'QRadical-chain reactions of sulfonyl azides and of ethyl azidoformate rnwith allylstannanes: homolytic allylation at nitrogen Hai-Shan Dang and Brian P. Roberts * LZ Christopher Ingold Laboratories, Department of Chemistry, University College London, 20 Gordon Street, London WClH OAJ, UK 4-Methylbenzenesulfonyl azide reacts with allyl triphenylstannane (ATPS) in refluxing benzene, in the presence of 2,2'-azobis(2-methylpropionitrile)as initiator, to give N-allyl-4-methylbenzenesulfonamidein good yield after hydrolytic work-up. Small amounts of allyl 4-methylphenyl sulfone were also formed. The reaction follows a free-radical chain mechanism which involves competitive addition of Ph,Sn' to Na and to N" of the azido group in ArSO,NaNbNc. Addition to Nafollowed by loss of nitrogen gives ArSOJWnPh,, tpe precursor of the N-allylarenesulfonamide,while addition to Ncleads to the formation of ArSO, and thence to the allyl aryl sulfone.Allyltrimethylstannane behaves in a similar way to ATPS, but allyltributylstannane gives only a low yield of N-allylarenesulfonamide and the major product is the unsubstituted sulfonamide MeC,H,SO,NH,, which results because the radical ArSOpSnBu, undergoes intramolecular 1,5-hydrogen-atom transfer in preference to adding to the allylstannane. 2-Methylallyltriphenylstannanereacts in an analogous way to ATPS, but allylstannanes containing non- terminal double bonds do not react successfully. The arenesulfonyl azides 4-XC,H4SO,N, (X= H, MeO, F) react in a similar way to tosyl azide, but the reaction is very sluggish when X = NO,.With 1-octanesulfonyl azide, reaction with Ph,Sn' is much less selective and products arising from attack at Na and Ncare formed in comparable yields. Ethyl azidoformate reacts with allylstannanes in a similar manner to, although more slowly than, tosyl azide and gives good yields ofthe corresponding allylic carbamates. The available evidence indicates that homolytic addition to an azide YN"NbN" can take place at either N" or N" to give a 3,3- triazenyl radical 1 or a I ,3-triazenyl radical 2, respectively (see Scheme l).' It is sometimes not clear to which end of the azido 1 2 Scheme 1 group addition occurs, because the ultimate products could plausibly arise from either intermediate triazenyl radical.For example, aryl, acyl and sulfonyl azides undergo induced decomposition when heated in propan-2-01 at 50-80 "C in the presence of diethyl peroxydicarbonate initi?tor and the key step was thought to involve reaction of Me,COH with the azide according to eqn. (l).3 It was proposed3 that addition of Me,cOH + YN, -YAH + Me,CO + N, (1) Me,tOH takes place initially at N" to give a 1,3-triazenyl radical, followed by intramolecular hydrogen-atom transfer from oxygen to N" with concerted elimination of acetone and molecular nitrogen. However, it seems equally possible that the 3,3-triazenyl radical YN(H)-N=N' is forTed initially, by hydrogen-atom transfer frqm oxygen in Me,COH, followed by loss of nitrogen to give YNH.Indeed, we have proposed that the reaction between Me,COH and a primary alkyl azide RCH,N3 to give the aminyl radical Me,C(OH)CH,fiR also involves attack at N", except that here 1,2-migration of the alkyl group R to nitrogen takes place in preference to hydrogen-atom transfer from oxygen. However, we have also reported that the EPR spectra observed during the generation of triorganosilyl radicals in the presence of a variety of types of azide are best jnterpreted as arising from 1,3-triazenyl adducts of the type YNNNSiR,.' The largest value of a(I4N) for these radicals arises from hyperfine coupling to the central nitrogen atom and the unpaired electron resides in a B molecular orbital symmetric to reflection in the NNN plane, as it does in the related 173-dialkyltriazenyl radical^.^ On the other hand, the r,eaction of trichloromethyl radicals with aryl azides to give ArNCC1, would appear much more likely to proceed by way of a 3,3-triazenyl ad$uct, rather than via an intermediate 1,3-triazenyl radical ArNNNCCl,, as originally suggested.Intramolecular addition of ary16 or alkyl' radicals to an azido function evidently takes place preferentially at N" to give intermediate 3,3-triazenyl radicals, which undergo subsequent loss of nitrogen to give cyclic aminyl radicals, and this reaction shows promise for organic synthesis. The reactions *-' of tributylstannyl radicals with alkyl an$ acyl azides appear to give stannylaminyl radicals of the type YNSnBu,. It seems likely that these radicals are formed following addition of Bu3Sn' to N", although addition to N" cannot be ruled out entirely because metallotropic interconversion of 1,3- and 3,3-triazenyl adducts could be rapid and it is even possible that the tin atom could bridge between N" and N" to form an intermediate containing a four-membered ring. Alkyl radicals react with alkane- and arene-sulfonyl azides at elevated temperatures to displace the corresponding sulfonyl radical [eqn.(2)J,I3 presumably via an intermediate 1,3-R' + ArSO,N,-RN, + ArSO, (2) triazenyl radical adduct. Thus, we conclude that quite subtle J. Chem. SOC.,Perkin Trans. 1,1996 1493 factors determine the relative rates of homolytic addition to Na and N" of the azido function and the balance can be tipped in either direction depending on the nature of the azide and of the attacking radical. For some reactant pairs, reversibility of addition to N" could also be important.The diazo group -CH=N, is isoelectronic with the azido group -N=N, and we have reported recently that a-diazocarbonyl compounds react with allyltributylstannane (ATBS) by a radical-chain mechanism to bring about allylation at carbon [eqn. (3)].14 Here Bu,Sn' evidently adds to the RC(O)CH=N, +Bu,SnCH,CH=CH, --+ RC(O)CH(SnBu,)CH,CH=CH, +N, (3) carbon atom of the -CH=N, group (analogous to N" of the azido group) to form a diaz:nyl radical, followed by rapid loss of nitrogen to give RC(O)CHSnBu, which then reacts with ATBS. The Bu,Sn group in the ultimate product [eqn.(3)] is readily replaced hydrolytically by H and thus the reaction of ATBS with a-diazo carbonyl compounds provides a new radical-mediated method for allylation at carbon a to a carbonyl group under non-basic conditions. Against this background, we have now investigated the reactions of sulfonyl azides with allylstannes I5-l8 with the aim of developing new methods for homolytic allylation at nitrogen. The corresponding reactions of benzoyl azide and of ethyl azidoformate have also been studied. Results and discussion Reactions of sulfonyl azides All reactions between sulfonyl azides and allylstannanes were carried out in refluxing benzene, under an atmosphere of nitrogen or argon, and were initiated by thermal decomposition of 2,2'-azobis(2-methylpropionitrile)(AIBN; 5 mol% based on sulfonyl azide).The reaction between benzenesulfonyl azide 3a and two molar equivalents of allyltriphenylstannane (ATPS) 4 was carried out under these conditions for 3 h, after which the mixture was treated with saturated aqueous potassium fluoride. After removal of Ph,SnF and a standard work-up, the crude product mixture was examined by 'H NMR spectroscopy. No sulfonyl azide remained and the only detectable products were N-allylbenzenesulfonamide 5a and allyl phenyl sulfone 6a, together with a trace amount of benzenesulfonamide 7a (see Scheme 2). The products were separated by flash chromato- graphy on silica gel and their identities were confirmed by comparison with the authentic compounds.No reaction took place in the absence of AIBN and, in the presence of initiator, the reaction could be inhibited with the nitroxide 2,2,6,6-tetramethylpiperidine-N-oxyl(5mol% based on sulfonyl azide), confirming the involvement of a free-radical chain mechanism. The proposed propagation sequence for the formation of the N-and S-allylation products is shown in Scheme 3 and involves competitive addition of the triphenylstannyl radical to N" and to N' of the azide, to give the 3,3-triazenyl radical 8 or the 1,3- triazenyl radical 9, respectively. Loss of nitrogen from the triazenyl radical 8 gives the electrophilic N-stannylsulfonamidyl radical 10, which then adds to the allylstannane, followed by p-scission of the adduct radical to give the N-allyl-N-stannyl- sulfonamide 11, hydrolysis of which yields the allylsulfon- amide 5.Fragmentation of the 1J-triazenyl radical 9 to give stannyl azide and an arenesulfonyl radical is followed by addition of the latter to the allylstannane'9 and p-scission of the adduct to give the allyl aryl sulfone 6. The reaction was repeated with the 4-substituted benzene- sulfonyl azides 3M, each of which was consumed completely under the reaction conditions, to give the corresponding N-allyl- arenesulfonamide 5b-d and allyl aryl sulfone 6M, along with small amounts of unsubstituted arenesulfonamide 7b-d, as the only detectable products (see Scheme 2). The yields of 1494 J. Chem. SOC.,Perkin Trans. I, 1996 02fN30 + Ph3Snw I 4X 3a-e a X=H b X=Me c X=MeO d X=F 8 X=NO, i, iiJ.5a-e 6a-e 7a-e Scheme 2 Reagents and conditions: i, AIBN, benzene, reflux; ii, KF-H2O R3Sn* + ArSO,N, J Ars02\N-N=N' R3Si 8 9 -R3SnN3i PlrSOL ArS02\ 11 \R3Sn71 6 H20 /F-Arsoz\ Hp-7, 5 Scheme 3 the sulfonamides 7a-d were determined by quantitative chrom- atographic isolation and, assuming that 5-7 are the only products deriving from the azides, the yields of N-allylarene- sulfonamides 5a-d and allyl arene sulfones 6a-d were estimated from the 'H NMR spectra of the crude reaction products. The reaction of 4-nitrobenzenesulfonyl azide 3e proceeded only to a small extent and most of the original azide was recovered unchanged; a 15% yield of the N-allylarenesulfonamide 5e was isolated by flash chromatography.The results are summarised in Table 1. Broadly similar results were obtained when allyltrimethyl- stannane (ATMS) was used in place of ATPS under otherwise identical conditions. For each of the azides 3a-d there was a Table 1 Yields of products from the reactions of arenesulfonyl azides 4-XC,H,S0,N3 3a-e with allyltriorganostannanes R,SnCH,CH=CH , Yield (%) 3 R (stannane) 5 6 7 aX = H Ph 91 5 4 Me 81 12 7 Bu 6 30 64 bX=Me Ph 89 8 3 Me 83 11 6 Bu 7 32 61 CX = Me0 Ph 86 10 4 Me 82 14 4 Bu 4 37 59 dX=F Ph 83 12 5 Me 72 20 8 BU 14 21 65 eX = NO, Ph 15 b b Bu c c c Based on arenesulfonyl azide.Only traces present. 'No significantreaction. modest decrease in the product ratio 5:6, although the N-allylarenesulfonamide 5 was still by far the major product, on going from ATPS to ATMS and again small amounts of the arenesulfonamide 7 were obtained. Although the major fate of the N-stannylsulfonamidyl radical 10 is addition to the allylstannane (Scheme 3), it appears that 10 also abstracts hydrogen to a small extent to give the N-stannylsulfonamide 12 [eqn. (4)], which would yield 7 after treatment with aqueous ArS(O,)kSnR, + H-Z +ArS(O,)N(H)SnR, + Z' (4)12 fluoride. The most probable hydrogen-atom donor H-Z would appear to be ATPS or ATMS, since the allylic C-H bonds in these compounds will be relatively weak.Very different results were obtained from the corresponding reactions of allyltributylstannane (ATBS) with sulfonyl azides. Compared with reactions involving ATPS or ATMS, the yields of the N-allylarenesulfonamides 5 are dramatically reduced, the yields of allyl aryl sulfones 6 (resulting from attack of the triorganostannyl radical at N")are increased, and there are large increases in the yields of the arenesulfonamides 7. We propose that the increase in the yield of 7 at the expense of 5 arises because the intermediate N-stannylsulfonamidyl radical 10 now undergoes relatively rapid intramolecular 1,5hydrogen-atom transfer, involving a butyl group attached to tin [eqn. (5)], to give the radical 13 which subsequently undergoes 13 radical-radical reactions or allylation by ATBS to give an N-stannylsulfonamide and thence 7 after treatment with aqueous fluoride.The rapidity of the inter- and intra-molecular reactions of the N-stannylsulfonamidyl radical 10 implies that this species is more reactive than an N-alkylsulfonamidyl radical." This would parallel the increased reactivity of N-trialkylsilylaminyl radicals compared with the corresponding radicals containing N-alkyl groups.2',22 For example, the reactivity of the bis(trimethy1silyl)aminyl radical (Me,Si),N' is much greater than that of Me," and more like that of an alkoxyl radical.,l Provided that only the reactions shown in Scheme 3 are involved and that reversibility of any addition process may be neglected, the yields of N-allylsulfonamide 5 and allyl aryl sulfone 6 will reflect directly the relative rates of addition of R,Sn' to N" and N" in the original sulfonyl azide.Inspection of Table 1 shows that, apart from 4-nitrobenzenesulfonyl azide which is unsatisfactory presumably because of interference by the nitrophenyl group with the propagation cycle, the electronic properties of the 4-substituent on the arenesulfonyl azide have little effect on the relative rates of attack of R,Sn' at N" compared with N". Of the triorganostannyl radicals, the tendency to add to N" (leading to N-allylation) decreases along the series Ph,Sn' > Me,Sn' > Bu,Sn', and the reaction of the crystalline 4-methylbenzenesulfonyl azide 3b with ATPS would appear to be the most suitable system for preparative N- allylation.In order to compare the behaviour of an alkanesulfonyl azide, the reactions of octane-1 -sulfonyl azide (OctSO,N,) with two molar equivalents of ATPS or ATBS were carried out under the same conditions; the results are summarised in Scheme 4.7The product yields indicate that both Ph,Sn' and OctSO,N, 2OctS0,NHAllyI + OctS0,Allyl + OctSO,NH, + R = Ph 56% 42% 2% ASfi3 R = BU 9% 36% 55% Scheme 4 Reagents and conditions: i, AIBN, benzene, reflux; ii, KF-H,O Bu,Sn' attack N" and N" at quite similar rates and thus the alkanesulfonyl azide is less suitable for selective N-allylation at nitrogen. In order to explore the limitations of N-allylation using arenesulfonyl azides and allylstannanes, the reactions of 4-methylbenzenesulfonyl azide with the three allyltriphenylstan- nanes 14-16 were carried out under the standard conditions 14 15 16 in refluxing benzene.Unfortunately, significant reaction took place with only the 2-methylallyl derivative 14, indicating that a terminal double bond is necessary to achieve a sufficiently high rate of radical addition to the allylstannane to maintain the chain. With the allylstannane 14, the azide was completely consumed and the N-2-methylallylsulfonamide 17 (86%) and the 2-methylallyl sulfone 18 (9%) were isolated by flash chromatography, together with a small amount of the sulfonamide 7b. 17 18 Reactions of benzoyl azide and of ethyl azidoformate The analogous reactions of benzoyl azide 19 and of ethyl azidoformate 20 with ATPS were also investigated under 19 20 21 similar conditions (2 molar equivalents of ATPS, AIBN initiator, refluxing benzene).Benzoyl azide gave mainly 1,3- 7 The product yields were estimated as described for the arenesulfonylazides. J. Chem. SOC.,Perkin Trans. I, I996 I495 diphenylurea after work-up, which presumably arises from hydrolysis of phenyl isocyanate, itself formed by thermally- induced Curtius rearrangement of the azide. Ethyl azido- formate, like the sulfonyl azides, does not undergo such rearrangement and ethyl N-allylcarbamate 21 was isolated in 45% yield from the reaction with ATPS (2.5 h reflux) after work-up with saturated aqueous potassium fluoride.However, cu. 50% of the azide remained unreacted and thus the reaction to give 21 is clean, but relatively slow. The allylcarbamate presumably arises by a route analogous to that shown in Scheme 3 for the formation of the N-allylsulfonamide 5 and involves attack of Ph,Sn' at N" of the azido group. Competitive addition to N" would give the 1,3-triazenyl radical 22 which- . EtOC(0)N zNZNSnPh3 EtOyNI-i& 22 0 23 does not break down readily to give EtO&O, in contrast to the corresponding sulfonyl azide adduct 9 which readily loses Ar$02. One probable fate of 22 is reversion to the azidoformate and Ph,Sn', but the triazenyl radical could also act as a scavenger for chain-carrying radicals, thereby inhibiting the formation of the N-allyl-N-stannylcarbamate and thus reducing the yield of 21.Under more forcing conditions (9 h total reaction time, with further additions of 3 mol% ATBN after 3 h and after 6 h), essentially all the azidoformate was consumed and the isolated yield of 21 increased to 74%. Under the same conditions, the reaction of ethyl azidoformate with the 2-methylallylstannane 14 afforded the N-allylic urethane 23 in an isolated yield of 78%. Since the free amine may be readily obtained by hydrolysis of such urethanes, the radical-chain reaction of allyltriphen ylstannanes containing terminal double bonds with alkyl azidoformates could provide a useful synthetic route to allylic amines. Experimental NMR spectra were recorded using a Varian VXR-400 instrument (400 MHz for 'H).The solvent was CDCI, and chemical shifts are reported relative to Me4Si; J values are quoted in Hz. Column chomatography and TLC were carried out using Merck Kieselgel 60 (230-400 mesh) and Kieselgel 60 F, 54 aluminium-backed precoated plates, respectively. All manipulations and reactions of air-sensitive compounds were carried out under an atmosphere of dry argon or nitrogen and all extracts were dried over anhydrous MgSO,. Petroleum refers to light petroleum (bp 40-60 "C). Materials Benzene was heated under reflux over metallic sodium, then distilled and stored over 4 8, molecular sievesunder argon. AIBN (Merck-BDH) was recrystallised from dichloromethane-petro- leum. Allyltributylstannane (ATBS) and allyltriphenylstannane (ATPS) (both Aldrich) were used as received.Allyltrimethylstan- nane (ATMS),,, 2-methylallyltriphenylstannane23 14 and 1-triphenylstannylbut-2-enel9 15 (cis + trans mixture) were prepared by a modified Grignard method 23 and 3-triphenyl- stannylcyclohexene 16 was prepared from 3-lithiocyclo- hexene, as described previously. Benzoyl azide 24 and ethyl azidoformate25[S, 1.30 (3 H, t, J 7.1) and 4.25 (2 H, q, J 7.1); 6, 14.0, 64.5 and 157.51 were prepared by literature methods. Sulfonyl azides These were prepared in 87-96% yield by the reaction of the corresponding sulfonyl chloride (50mmol) with sodium azide (55 mmol) in aqueous ethanol, following the standard procedure. 26 1496 J. Chem.SOC.,Perkin Trans. I, 1996 Benzenesulfonyl azide27 3a. Obtained as an oil which solidified on standing at 5 "C; 6, 7.62 (2 H, m), 7.74 (1 H, m) and 7.96 (2 H, m); 6,127.4, 129.7, 134.8 and 138.4. 4-Methylbenzenesulfonyl azide 28 3b. Obtained as an oil which solidified on standing at 5 "C, mp 20 "C (lit.,28 mp 19-20 "C);6, 2.48(3H,s),7.42(2H,d,J8.4)and7.83(2H,d,J8.4);6,21.7, 127.4, 130.2, 135.3 and 146.2. 4-Methoxybenzenesulfonyl azide29 3c. Recrystallised from CH2C1,-petroleum, mp 54 "C (lit.,29 mp 55 "C); 6, 3.91 (3 H, s), 7.05 (2 H, d, J9.0) and 7.90 (2 H, d, J9.0);6, 55.8, 114.7, 114.9, 129.9 and 164.6. 4-Fluorobenzenesulfonyl azide 3d. Recrystallised from CH,CI,-petroleum, mp 35-36 "C; 6, 7.31 (2 H, dd, JHH 8.45, JHF 8.33) and 8.00 (2 H, dd, JHH8.45, JHF4.98); 6, 117.1 (d, JCF 23.0), 130.5 (d, JCF9.8), 134.4 (d, JCF 3.1) and 166.3 (d, JCF 25 7.2).4-Nitrobenzenesulfonyl azide31 3e. Recrystallised from CH,CI,-petroleum as pale yellow needles, mp 101-102 "C (lit.,31 mp 101.5-102 "C); 6, 8.17 (2 H, m) and 8.46 (2 H, m); 6, 124.9, 128.9, 143.7 and 151.2. 1-Octanesulfonyl azide. Prepared in 85% yield following the method used for the arenesulfonyl azides; it was an oil which solidified on standing at 5 "C;BH 0.88 (3 H, t, J 6.7), 1.31 (8 H, m), 1.45(2H,m), 1.91 (2H,m)and3.30(2H,m);6,14.0,22.5, 23.3, 27.9, 28.8(2), 28.8(4), 31.6 and 55.9 (Found: C, 43.8; H, 7.9; N, 19.2. C,H,,N,O,S requires C, 43.8; H, 7.8; N, 19.2%). General procedure for reactions of sulfonyl azides with allyltriorganostannanes A solution containing the sulfonyl azide (2.0 mmol), the allylstannane (4.0 mmol) and AIBN (17 mg, 0.10 mmol) in benzene (6 cm3) was heated under reflux for 3 h under an atmosphere of argon.The reaction mixture was allowed to cool to room temperature, diluted with diethyl ether (15 cm3) and shaken vigorously with saturated aqueous potassium fluoride (15 an3).The precipitate was removed by filtration and washed with diethyl ether. The organic layer was separated from the filtrate and the aqueous layer was extracted with diethyl ether (3 x 20 cm3). The combined organic phase was washed with saturated brine, dried and the solvent removed under reduced pressure. The rcsidue was examined by 'H NMR spectroscopy to determine the relative yields of N-allylarenesulfonamide and ally1 aryl sulfone, by integration of the characteristic signals from the allylic protons.The residue was subjected to flash chromatography, eluting successively with petroleum (to remove unreacted ATMS or ATBS) or petroleum-diethyl ether (10: 1) (to remove ATPS), followed by petroleumcliethyl ether (5:1) to obtain the allylsulfonamides 5 and ally1 aryl sulfones 6, followed by petroleum-diethyl ether-CH,Cl, (2 :1:1) to obtain the sulfonamides 7. The yields are given in Table 1 and the analytical data are given below. N-Allylbenzene~ulfonamide~~5a. A viscous oil; 6, 3.60 (2 H, m), 4.81 (1 H, br t, Jca. 6, NH), 5.08 (1 H, dd, J 10.3, 1.2), 5.16 (1 H, dd, J 16.0, 1.2), 5.70 (1 H, ddt, J 16.0, 10.3,6.1), 7.51 (2 H, m), 7.58 (1 H, m) and 7.88 (2 H, m); 6,45.7, 117.7, 127.0, 129.1, 132.7, 132.8 and 139.9.N-Allyl-4-methylbenzenesulfonamide33 5b. Mp 63-65 "C (lit.,,, mp 65-66 "C); BH 2.43 (3 H, s). 3.57 (2 H, m), 4.82 (1 H, br t, Jca. 6.1, NH), 5.08 (1 H, dd, J 10.3, 1.3), 5.16 (I H, dd, J 17.1, 1.3), 5.70 (1 H, ddt, J 17.1, 10.3, 6.0), 7.30 (2 H, d, J 8.0) and7.76(2H,d,J8.0);6,21.5,45.7, 117.6, 127.1, 129.7, 132.9, 136.8 and 143.4. N-Allyl-4-methoxybenzenesulfonamide34 5c. Mp 45 "C (lit. ,34 mp 45-47 "C);6, 3.56 (2 H, m), 3.86 (3 H, s), 4.71 (1 H, br t, Jca. 6, NH), 5.08 (1 H, dd, J 10.3, 2.3), 5.15 (1 H, dd, J 18.5, 2.3), 5.71 (1 H, ddt, J 18.5, 10.3, 5.9), 6.97 (2 H, d, J9.0) and 7.80 (2 H, d, J 9.0); 6, 45.7, 55.6, 114.2, 117.6, 129.2, 131.4, 133.0 and 162.9.N-Allyl-4-fluorobenzenesulfonamide5d. Mp 53 "C; 6, 3.60 (2 H, ni), 4.73 (1 H, br t, Jca. 6, NH), 5.09 (1 H, dd, J 10.3, 1.2), 5.16(1 H,dd, J17.1, 1.2)and5.70(1 H,ddt, J17.1, 10.3,6.0);6, 45.7, 116.3 (d, JCF 9.4), 132.7, 136.0 22.5), 117.9, 129.8 (d, JCF (d, JCF3.2) and 165.0 (d, JCF254.7) (Found: C, 50.2; H, 4.7; N, 6.5. C,H,,FNO,S requires C, 50.2; H, 4.7; N, 6.5%). N-Allyl-4-nitrobenzenesulfonamide35 5e. Mp 1 12-1 13 "C (lit.,35mp113-l13.50C);6H3.70(2H,m),4.75(1H,brt,Jca. 6, NH), 5.15 (1 H, dd, J 10.2, 1.1), 5.19 (1 H, dd, J 17.1, 1.1), 5.73 (1 H, ddt, J 17.1, 10.2,6.7), 8.10 (2 H, m) and 8.45 (2 H, m); ~5~45.9.118.4, 124.5, 128.4, 132.4, 146.1 and 152.3. N-Allyl-l-octanesulfonamide.Mp 43 "C; 6, 0.87 (3 H, t, J 7.1), 1.27 (8 H, m), 1.39 (2 H, m), 1.78 (2 H, m), 3.00 (2 H, m), 3.73(2H,m),4.78(1 H,brm,NH),5.18(1 H,dd,JlO.l,l.l), 5.28(1 H,dd,J17.1, l.l)and5.85(1 H,ddt, J17.1, 10.1,5.9);6, 14.0,22.6,23.6,28.2,28.9,29.0,31.7,45.6,53.2,117.6and 133.7 (Found: C, 56.6; H, 10.0; N, 6.0.C, 1H,3N02S requires C, 56.6; H, 9.9; N, 6.0%). Allyl phenyl sulfone 36 6a. An oil; 6,3.80 (2 H, d, J7.3), 5.13 (1 H, dd, J 17.0, 1.2), 5.32 (1 H, dd, J 10.1, 1.2), 5.78 (I H, ddt, J 17.0, 10.1,7.3),7.55(2H,m),7.65(1 H,m)and7.87(2H,m);dC 60.8, 121.4, 124.7, 128.4, 129.0, 133.7and 137.0. Allyl 4-methylphenyl ~ulfone~~ 6b. Mp 59 "C (lit.,37 mp 58oC);6,2.42(3H,s),3.77(2H,d,J7.4),5.13(1H,dd,J17.l, 1.0),5.31(I H,dd, J10.1, l.O), 5.760 H,ddt, J17.1, lO.l,7.4), 7.32 (2 H, d, J8.4) and 7.72 (2 H, d, J8.4); 6,21.6, 60.8, 124.6, 128.4, 129.4, 129.7, 135.2and 144.7.Allyl 4-methoxyphenyl ~ulfone~~ 6c. An oil; 6, 3.77 (2 H, d, J 7.4), 3.87 (3 H, s), 5.13 (1 H, dd, J 17.1, l.l), 5.30 (I H, dd, J 10.2, l.l), 5.77 (1 H, ddt, J 17.1, 10.2, 7.4), 7.00 (2 H, d, J8.9) and7.77(2H,d, J8.9);6,55.6, 61.1, 114.2, 124.4, 124.9, 129.2, 130.6 and 163.7. Allyl 4-fluorophenyl sulfone 39 6d. Mp 46"C(lit.,39 mp 47 "C); ~5~3.81(2H,d, J7.4),5.15(1 H,dd, J17.1,1.1),5.35(1 H,dd,J lO.l,I.l),5.79(1H,ddt,JI7.1,10.0,7.4),7.23(2H,d,J8.9,8.4) and7.89(2H,dd, J8.9, 5.1);6,61.0, 116.3(d, JCF22.7), 124.7, 124.9, 131.3 (d, JCF9.6), 134.2 (d, JCF3.1) and 165.8 (d, JCF 256.2). Allyl oct-l-yl sulfone.An oil; 6, 0.87 (3 H, t, J 6.6), 1.28 (8 H, m), 1.41 (2 H, m), 1.81 (2 H, m), 2.93 (2 H, m), 3.69 (2 H, d, J 7.4), 5.43 (1 H, dd, J 17.0, 1.0), 5.48 (1 H, dd, J 10.1, 1.0) and 5.93 (1 H, ddt, J 17.0, 10.1, 7.4);6, 14.0, 21.7, 22.5, 28.4, 28.9, 29.0, 31.7, 51.2, 57.6, 124.4 and 125.2 (Found: C, 60.6; H, 10.0. C, ,H,,O,S requires C, 60.5; H, 10.2%). Sulfonamides 7a4. The melting points of the unsubstituted sulfonamides 7a4 agreed with those given in the literat~re.~' Benzenesulfonamide 7a, mp I 50-1 5 I "C; 4-methylbenzenesul-fonaniide 7b, mp 1 37-1 39 "C; 4-methoxybenzenesulfonamide 7c, mp 1 10-1 12 "C and 4-fluorobenzenesulfonamide 7d, mp 124-125 "C. l-Octanesulfonamide. Mp 67-68 "C (lit.,41 mp 68-69 "C). N-(2-methylallyl)-4-methylbenzenesulfonamide42 17.Mp 49 "C (lit.,42 mp 50-52 "C);6, 1.67 (3 H, s), 2.42 (3 H, s), 3.47 (2 H, d, J6.5), 4.75 (1 H, br t, Jca. 6.5, NH), 4.81 (1 H, s), 4.85 (1 H,s), 7.72(2H,d, JS.l)and7.75(2H,d, J8.1);6,20.1,21.5, 49.0, 112.7, 127.7, 130.0, 136.9, 140.5 and 143.4. 2-Methylallyl 4-methylphenyl s~lfone~~ 18. Mp 70-7 1 "C (lit.,43 mp 70.5-71.5 "C); 6, 1.85 (3 H, t, J l.O), 2.44 (3 H, s), 3.73 (2 H, s),4.68 (1 H, m), 5.02(1 H, m), 7.33 (2 H, d, J8.5) and 7.74(2H,d, J8.5);6,21.6,22.7,64.5, 120.6, 128.5, 129.6, 133.5, 135.4 and 144.6. Reactions of ethyl azidoformate 20 A solution in benzene (6 cm3)containing ethyl azidoformate (2 mmol), allyltriphenylstannane (4 mmol) and AIBN (0.1 mmol) was heated under reflux for 2.5 h, as described for the reactions of sulfonyl azides.After work-up as described before, ethyl N-allylcarbamate 44 21 (45%) was obtained as an oil, together with unreacted azide (50%); 6, 1.24 (3 H, t, J 7.0), 3.80 (2 H, br m), 4.12 (2 H, q, J 7.0), 4.79 (I H, br s, NH), 5.12 (I H, dd, J 10.3, 1.4). 5.18 (I H, dd, J 17.2, 1.4) and 5.84 (I H, ddt, J 17.2, 10.3, 6.8);6, 14.6, 43.3, 60.8, 115.8, 134.6 and 156.6. When the reaction was repeated, but with an initial reflux time of 3 h, followed by addition of ATBN (0.06 mmol) and further heating for 3 h, then addition of more AIBN (0.06 mmol) and heating for an additional 3 h, the yield of urethane 21 was increased to 74%. Under these conditions, the reaction of ethyl azidoformate with 2-methylallyltriphenylstannane14 afforded ethyl N-2-methylallylcarbamate45 23 in 78% yield; 6, 1.21 (3 H, t, J7.5), 1.70 (3 H, s), 3.68 (2 H, d, J6.0), 4.09 (2 H, q, J 7.5) and 4.75-4.90 (3 H including NH, m); 6, 14.7, 20.2,46.6, 60.9, 110.6, 142.4 and 156.7.Acknowledgements We thank the EPSRC for support. References 1 B. P. Roberts and J. N. Winter, J. Chem. Soc., Perkin Trans. 2, 1979, 1353. 2 R. A. Abramovitch and E. P. Kyba, in The Chemistry of the Azidu Group, ed. S. Patai, Interscience, New York, 1971, ch. 5. 3 L. Horner and G. Bauer, Tetrahedron Lett., 1966,3573. 4 J. C. Brand and B. P. Roberts, J. Chem. Sue., Chem. Commuri., 1981, 748; J. Chem. Soc., Perkin Trans. 2, 1982, 1459. 5 J. E. Leffler and H. H. Gibson, Jr., J. Am. Chew. Suc., 1968,90,4117. 6 L.Benati, P. C. Montevecchi and P. Spagnolo, Tetrdzedron Lett., 1978,815; L. Benati and P. C. Montevecchi, J. Org. Chem., 1981,46, 4570. 7 S. Kim, G. H. Joeand J. Y. Do, J, Am. Chem. Soc., 1994,116,5521. 8 M. Frankel, D. Wagner, D. Gertner and A. Zilka, J. Organomet. Chem., 1967,2, 518. 9 H. Redlich and W. Roy, Liehigs Ann. Chem., 1981, 121 5. 10 S. Kim, G. H. Joe and J. Y. Do, J. Am. Chem. Soc., 1993, 115, 3328. 11 S. Kim and J. Y. Do, J. Chem. Soc., Chem. Commun.. 1995, 1607. 12 S. Kim, K. S. Yoon, S. S. Kim and H. S. Seo, Tetrahedron, 1995,51, 843 7. 13 M. F. Sloan, W. B. Renfrow and D. S. Breslow, Tetrahedron Lett.. 1964,2905; D. S. Breslow, M. F. Sloan, N. R. Newburg and W. B. Renfrow, J. Am. Chem. Soc., 1969,91,2273;R.A. Abramovitch and W. D. Holcomb, J. Chem. Soc., Chern. Cumrnun., 1969, 1298. 14 H.-S.Dang and B. P. Roberts, J. Chem Soc., Perkiiz Trans. I, 1996, 769. 15 G. E. Keck and J. B. Yates, .J. Am. Chem. Soc., 1982, 102, 5289; G. E. Keck, E. J. Erholm, J. B. Yates and M. R. Wiley, Tetrtihec/ron, 1985,41,4079. 16 D. P. Curran, Synthesis, 1988,489. 17 W. B. Motherwell and D. Crich, Free Radicd Chain Reactions in Organic Synthesis, Academic Press, London, 1992, pp. 202-207. 18 Y. Yamamoto and N. Asoa, Chem. Rev., 1993,93, 2207. 19 G. A. Russell and L. L. Herold, J. Org. Chem.. 1985,50, 1037. 20 G. Somer and J. B. F. N. Engberts, Tetrahedron Lett., 1977, 3901; H. Teeninga and J. B. F. N. Engberts, J. Org. Chem., 1979,44,4717; W. C. Danen and R.W. Gellert, J. Am. Chem. Suc., 1979,102, 3264: R. Sutcliffe, M. Anpo, A. Stolow and K. U. Ingold, J. Am. Chem. Soc., 1982,104,6064. 21 B. P. Roberts and J. N. Winter, J. Chem. Sue., Chern. Commun., 1978,545; J. C. Brand, B. P. Roberts and J. N. Winter, J. Chem. Soc., Perkin Truns.2., 1983,261. M. D. Cook, B. P. Robertsand K. Singh, J. Chem. Sot-.,Perkin Trans. 2, 1983, 635. 22 J. C. Brand, M. D. Cook and B. P. Roberts, J. Chem. Soc., Perkin Trans. 2, 1984, 1187. 23 H.-S. Dang and A. G. Davies, J. Chem. Soc., Perkin Trans. 2, 199I, 201 1; J. Organomet. Chem., 1992,430, 287. 24 B. C. Ranu, A. Sarkar and R. Chakraborty, J. Org. Chem.. 1994,59, 41 14. 25 P. Frayen, Phosphorus, Sulfur Silicon Relat. Elem., 1993,78, 161. 26 M.Regitze, J. Hooker and A. Liedhegener, Org. Synth., 1973, Coll. Vol. 5. 179. 27 J. E. Leffler and Y. Tsuno, J. Org. Chern., 1963, 28, 902; M. T. Reagan and A. Nickon, J. Am. Chem. Soc., 1968,90,4096. 28 D. L. Rector and R. E. Harmon, J. Org. Chem., 1966,31, 2837. 29 L. Horner and A. Christmann, Chem. Ber., 1963,96,388. 30 C. Garganta, J. Hazelett and J. M. Shaw, Biochem. Bioplzys. ActLi, 1985,812,261;R. M. Moriarty and M. Rahman, J. Am. Cizetn. Soc., 1966, 88, 842. 31 S. M. Kumar, Synth. Comnzun., 1987, 17, 101 5. 32 A. J. Hurbert, A. Ferson, G. Goebbels, R. Warin and P. Teyssie, J. Chern. Soc., Perkin Trans. 2, 1977, 11. J. Chem. SOC.,Perkin Trans. 1, 1996 1497 33 N. M. Sanghavi, V. L. Parab; B. S. Patravale and M. N. Patel, Synth. Commun., 1989,19, 1499. 34 A. Fabrycy, J. Kaszubska, W. Jacobson and M. Gwiazda, Pr. Inst. Przem. Org., 1973, 5, 223 (Chetn. Abstr., 1975,83, 192957a). 35 J. Petranek and M. VeCefa, Collect. Czech. Chenz. Commun., 1959, 24, 2191. 36 J. Dunogues and R. Calas, Synthesis, 1977,469. 37 J. Wildeman and A. M. van Leusen, Synthesis, 1979,733. 38 K. H. Bell, J. Chem. Soc., Perkin Trans. 1, 1988, 1957. 39 B. D. Gupta, S. Roy and S. Sen, Indian J. Chem., Sect. B, 1985,24, 1032. 40 M. Ludwig, 0. Pytela, K. Kalfus and M. VeEeia, Collect. Czech. Chem. Commun., 1984,49, 1184. 41 M. S. Kharasch and R. A. Mosher, J. Org. Chem., 1952,17,453, 42 T. Kataoka, M. Yoshimatsu, Y. Noda, T. Sato, H. Shimizu and M. Hori, f,Chem. Soc., Perkin Trans. I, 1993, 121. 43 J. K. Crandall and C.Pradat, J. Org. Chern., 1985,50, 1327. 44 S. P. McManus and J. T. Carroll, f.Org. Chem., 1970,35, 3768. 45 J. L. Brewbaker and H. Hart, J. Am. Chem. Soc., 1969, 91, 711; E. Kleinpeter, R. Widera and M. Muhlstadt, Z. Chem., 1977, 17, 267. Paper 6/014025 Received 27th February 1996 Accepted 2 1st March 1996 1498 J. Chem. SOC.,Perkin Trans. I, 1996