首页   按字顺浏览 期刊浏览 卷期浏览 Chapter 10. Organometallic chemistry. Part (i) The transition elements
Chapter 10. Organometallic chemistry. Part (i) The transition elements

 

作者: D. Parker,  

 

期刊: Annual Reports Section "B" (Organic Chemistry)  (RSC Available online 1984)
卷期: Volume 81, issue 1  

页码: 211-226

 

ISSN:0069-3030

 

年代: 1984

 

DOI:10.1039/OC9848100211

 

出版商: RSC

 

数据来源: RSC

 

摘要:

10 Organometallic Chemistry Part (i)The Transition Elements By D. PARKER Department of Chemistry University of Durham South Road Durham DH13LE 1 Introduction 1984 was a year in which organotransition metal chemistry was applied successfully to several synthetic problems notably asymmetric carbon-carbon bond forming reactions. Several useful texts and reviews appeared including Volume 2 of the Patai series on the metal-carbon bond,’ a summary of leading developments in homogeneous catalysis and another monograph on the application of transition metals to organic synthesis3 Leading reviews appeared on the use of metal carbenes in synthesis the photochemistry of transition metal alkyls,’ aspects of organocopper cobalt mediated cycloadditions,8 palladium-assisted reactions of mono- olefins,’ palladium and mercury catalysed sigmatropic rearrangements,” and transi- tion metal trialkylsilane complexes.’ A timely text discussed olefin metathesis and ring-opening polymerization of cyclo-olefins,12 topics which were also Notable articles appeared lying outside the scope of this report on carbon-carbon bond activation in unstrained alkanes,” the catalytic chlorination of methane,16 the mechanism of nickel catalysed HCN addition to alkenes,”-19 and the development of a modified flash chromatography procedure for the purification of air-sensitive organometallics.20 ‘The Chemistry of the Metal-Carbon Bond’ ed.F. R. Hartley and S. Patai Vol. 2 John Wiley New York 1984. ‘Fundamental Research in Homogeneous Catalysis’ ed.M. Graziani and M. Giongo Vol. 4 Plenum New York 1984. ‘New Pathways for Organic Synthesis. Practical Applications of Transition Metals’ H. M. Colquhoun Plenum New York 1984. K. H. Dotz Angew. Chem. Znr. Ed. Engl 1984 23,587. ’ H. G. Alt Angew. Chem. Znf. Ed. Engl. 1984 23,766. J. Lindley Tetrahedron 1984 40 1433. ’ B. H. Lipshutz R. S. Wilhelm and J. A. Kozlowski Tetrahedron 1984.40 5005. * K. P. C. Vollhardt Angew. Chem. Inr. Ed. Engl. 1984 23,539. L. S. Hegedus Tetrahedron 1984. 40,2415. lo L. E. Overman Angew. Chem. Int. Ed. Engl. 1984 23,579. ‘I J. A. Gladysz Acc. Chem. Res. 1984 17 326. 12 ‘Olefin Metathesis and Ring Opening Polymerisation of Cyclo-Olefins’ V. Dragutan A. T. Balaban and M. Dimonie John Wiley Chichester 1984.I’ B. A. Dolgoplask and E. I. Tinyakova Usp. Khim. 1984 53,40. 14 B. A. Dolgoplask and Y. V. Korshak Usp. Khim. 1984 53,65. R. H.Crabtree and R. P. Diou J. Chem. SOC. Chem. Commun. 1984 1260. 16 N. Kitajima and J. Schwartz J. Am. Chem. SOC. 1984 106 2220. 17 C. A. Tolman W. C. Seidel J. D. Druliner. and P. J. Domaille Organornetallics 1984 3,33. 18 J. D. Druliner Organornetallics 1984 3,205. 19 R.J. McKinney and D. C. Roe J. Am. Chem. SOC. 1985 107 261. 20 K. A. M.Kremer and P.Helquist Organomerallics 1984 3,1743. 211 212 D. Parker 2 Metal-promoted Alkylations Acylations and Vinglations Iron acyl complexes have long been recognized as useful in synthesis because of the range of mild decomplexation methods permitting their conversion into a variety of carbonyl functionalities.A series of articles has reported diastereoselective carbon-carbon bond formation based on elaboration of the acyl ligand of (1). Treatment of (1) with base followed by alkylation leads to the diastereoisomeric acyl (2) while reaction of the methoxycarbene (3) with base gives a methoxyvinyl complex which may be alkylated to give the opposite diastereoisomer (4) (Scheme 1).21*22 Similar methods permit the stereoselective synthesis of quaternary carbon i. BuLi i. BuLi ii. PhCH,Br ii. PhCH,Br I I Scheme 1 atoms leading to chiral 2,2-dialkylb~tyrolactones.~~ More significantly this methodology has led to the development of a chiral acetate enolate equivalent for the synthesis of P-hydroxy acids with 3200 :1 diastereoselectivity ! Condensation of the dialkylaluminium enolate of (5) with carbonyls at low temperature gives rise to the P-hydroxyacyl complex (6) (3100 l) with the P-alkyl group preferring the least hindered position in the transition state and in the initial aluminium chelated product directed away from the phenyl group of the PPh3 ligand.Further elaboration of the acyl permits the synthesis of the erythro disastereoisomer (7) with 3200 1 diastereoselectivity (Scheme 2) .24*25 Imines also condense stereoselectively with (5) to give P-aminoacyl iron complexes which may be oxidatively cyclized to p-~actams.~~.~~ 21 G. J. Baird J. A. Bandy S. G. Davies and K. Rout J. Chem. Soc. Chem. Commun. 1983 1202. 22 G.J. Baird S. G. Davies R. H. Jones K. Prout and P. Warner J. Chem. SOC.,Chem. Cornmun. 1984,745. 23 P. J. Curtis and S. G. Davies J. Chem. Soc. Chem Commun. 1984 747. 24 S. G. Davies I. M. Dordor and P. Warner J. Chem. SOC.,Chem. Commun. 1984 956. 2s S. G. Davies I. M. Dordor J. C. Walker and P. Warner Tetrahedron Lett. 1984 25 2709. 26 L. S. Liebeskind M. E. Welker and V. Goedken J. Am. Chem. SOC.,1984 106 441. 27 K. Broadley and S. G. Davies Tetrahedron Lett. 1984 25 1743. 213 Organometallic Chemistry -Part (i) The Transition Elements i. BuLi ii. Me1 Ph,P iii. HIO iv. BrJH,O H OH (6) (7) Scheme 2 The regio- and stereo-controlled functionalization of cycloheptadiene~~~*~~ and cyclohexene~~~ using organoiron organomanganese and organomolybdenum car- bony1 complexes has been reported.Reaction of (8) with stabilized enolate nucleophiles gives an intermediate .rr-allyl (9) which was converted into the lactone (10) using a modified iodolactonization demetallation procedure;l (Scheme 3). MO(CO),CP C0,Me ,cp -CH(CO,Me), 0 o:yob _____* ii.yH/MeOH /M? (CO,Me),HC” iii. H,O+ ‘I oc co (8) (9) (10) Scheme 3 A highly enantioselective homoaldol addition reaction with chiral N-allylureas mediated by organotitanium species has facilitated the synthesis of a series of chiral y-lactone~.~~ Reaction of (1 1) with base followed by TiCl( NEt,) gave the stabilized titanium alkyl (12) which condensed stereoselectively with a series of carbonyls to give the enamide (13) which may be readily converted into the desired lactone (14) (Scheme 4).The reaction of 1,3-dialkyl-substituted ally1 anions with aldehydes is mediated by v3-allyltitanium compounds facilitating a synthesis of hydroxy- substituted cy~loalkanes.~~ Similarly the allylmetallation of alkynes has been shown to assist the synthesis of various cycloalkenes in the presence of C1,ZrCp2. Reaction of allyldi-isobutylalane with terminal alkynes mediated by Cp2ZrC12 gives the cis monoallylation product as two constitutional isomers permitting a general method for converting terminal alkynes into various penta-l,4-diene derivative^,^^ (Scheme 5). A convergent approach has joined a masked conjugated diene with a potential dienophile in a metal-catalysed alkylation reaction.Each partner may be readily assembled individually and the sensitive intermediate is generated under very mild alkylation conditions immediately prior to intramolecular cycloaddition. The nature of the Diels-Alder reaction is governed by the regioselectivity of the alkylation which depends upon the choice of the metal template. Thus alkylation of (15) with 28 A. J. Pearson S. L. Kole and T. Ray J. Am. Chem. SOC.,1984 106 6060. 29 A. J. Pearson P. Bruhn and I. C. Richards Tetrahedron Lett. 1984 25 387. 30 A. J. Pearson M. Khan and I. Nazrul Tetrahedron Lett. 1984 25 3507. 31 A. J. Pearson M.Khan and I. Nazrul,J. Am. Chem. SOC.,1984 106 1872. 32 H. Roder G. Helmchen E. M.Peters K. Peters and H. G. Van Schnering Angew. Chem Znt. Ed.Engl. 1984 23 898. 33 Y. Kobayashi K. Umeyama and F. Sato J. Chem. Soc. Chem Commun. 1984 621. 34 J. A. Miller and E. Negishi Tetrahedron Lett. 1984 25 5863. 214 D. Parker 0 __--Ti( NEt,) i. BuLi -b MeN ii. (NEt,),TiCI ,\ Me Ph Me I. Ph (1 1) (12) R*R~CO x MeOH MeN NCH=CHCH,-C--R' R2-&Lo I 4 LJ ii. BFJMCPBA R' Me Ph (14) (13) Scheme 4 major minor Scheme 5 the stabilized carbanion (16) is mediated by Mo(CO) to give after hydrolysis the aldehyde (17) which may be cyclized under Lewis acid catalysis to give the tricyclic pyran (18) (Scheme 6). Similarly reaction of (19) with the carbanion (20) in the presence of (MeCN) W(CO)3 proceeds uia exclusive internal attack on the inter- mediate wallyl to give (21) which is readily cyclized to (22) (Scheme 7).35 Metal alkyls and aryls are usually extremely sensitive to moisture but the chromium alkyls such as (THF),Cl,Cr-R (R = Me Bun allyl) permit the alkylation of carbonyls under mild conditions in protic media to give the corresponding 1-Bromoallenes may be converted into phenyl-substituted allenes with inversion of configuration in the allenyl moiety by reaction with diphenylzinc in the presence of Pdo(PPh3),;37 reaction of (R)-(23) generates (S)-(24).A series of heterocycles may be synthesized via a stepwise thallation and palladium-promoted vinylation sequence; reaction of (25) gives (26) in high yield while (27) gave the benzopyran (28) ~electively.~~ 2-Bromo-l,6-dienes are catalytically cyclized to give conjugated five-membered bis-exocyclic dienes and six-membered mono-exocyclic dienes under 35 B.M. Trost M.Lautens M. Lautens M. H.Hung and C. S. Carmichael J. Am. Chem SOC.,1984 106 7641. 36 T. Kauffmann R. Abeln and D. Wingbermuhle Angew. Chem. Int. Ed. Engl 1984 23 729. 37 C. J. Elsevier H. H. Mooiweer H. Kleijn and P. Vermeer Tetrahedron Lett. 1984 25 5571. 38 R. C. Larock C. L. Liu H. H. Lau. and S. Varaprath Terrahedron Lett. 1984 25 4459. Organometallic Chemistry -Part (i) The Transition Elements MeAICI CH,CI i (18) Scheme 6 Scheme 7 rhodium and palladium catalysis (Scheme 8). RhCl(PPh3)3 catalyses formation of the 5-exo-trigonal product while Pd( PPh3)4 favours the 6-endo ring-clo~ure.~~ The bis-exocyclic dienes undergo Diels- Alder reactions in high yield so that the attractive combination of consecutive metal-catalysed creation of Diels- Alder precursors with Diels-Alder cycloadditions is partially realised (uiz.Schemes 6 and 7). In a related reaction RuC12( PPh3) catalyses cyclization of N-allyltrichloroacetamides to give the corresponding y-butyrolactams in good yield:’ (29) -+ (30). Copper( I) chemistry continues to attract considerable interest and the alkenyl copper reagents have again proved remarkably versatile. The carbocupration of acetylenic acetals and ketals has facilitated synthesis of geranial and 2,4-(E,Z)-diena1s;l while the amidomethylation of alkenylcopper reagents permits the syn- thesis of various allylic amides?2 Thus reaction of (31) with the formamide deriva- tives (32) generates the allylic amide (33) which may be readily converted into the corresponding amine.The chiral epoxide (34) reacts stereospecifically with the 39 R. Grigg P.Stevenson and T. Worakun J. Chem. SOC.,Chem Commun. 1984 1072. 40 H. Nagashima H. Wakamatsu and K. Itoh J. Chem. SOC.,Chem. Commun. 1984 652. 41 A. Alexakis A. Commercon C. Coulentoanos and J. F. Normant Tetrahedron 1984,40 715. 42 G. Germon A. Alexakis and J. F. Normant Svnthesis 1984 40. 216 D. Parker R,. H -Ph / Ph,Zn R. / H/c=c=c \Br Pd(PPh3) )'='=' \ H H u Li PdCl /MeCN aco2,& H,C=CHR ' 'R T 1 (CF,C02)2 X=Y=H X = Y = CO,Et X = Y = COMe X = Me,Y = COPh xy xy xy Scheme 8 CI,CCONHCH,CH=CH2 (29) H H xR2 -HR2 + CICH,NMeCHO ~1 CuLi R' CH,NMeCHO (32) (31) (33) alkenylcopper reagent (35) to generate the allylic alcohol (36).Repeating such reactions in sequence has permitted the synthesis of chiral all syn 1,3-p0lyols.~~ Nuclear magnetic resonance and X-ray crystallographic studies have revealed that the Reformatsky reagent exists as a dimer in both solution and in the solid-state and dissociates into a monomer only in very polar solvents such as DMSO.@Finally 43 B. H. Lipshutz and J. A. Koslowski J. Org. Chern. 1984,49 1147. 44 J. Boersma G. J. M. Van der Kerk and A. J. Spek Organornerallics 1984 3 1403. Organometallic Chemistry -Part (i) The Transition Elements 217 PhCH,OCH P (H2C=CH)2Cu(CN)Li2 PhCH20CH2CH(OH)CH2CH=CH2 (34) (3 5) (36) in contrast to the highly diastereoselective stoicheiometric carbon-carbon bond- forming reactions discussed earlier in this section a highly promising enantioselec- tive catalytic carbon-carbon bond-forming reaction has been de~cribed.~' The pres- ence of a cobalt(I1) diamine complex of (S,S)-(+)-1,2-diphenyl-l,2-ethanediamine catalyses the Michael addition of methyl vinyl ketone with P-keto esters.Reaction of (37) with (38) at -50 "C generates the corresponding 1,5-dicarbonyl (39) with 66% enantiomeric excess. 3 Nucleophilic Attack on Co-ordinated n-Ligands The enhanced susceptibility to nucleophilic attack of co-ordinated digands has once more facilitated many important syntheses.The anti-tumour agent 1 1 -deoxyan- thracyclinone (40) has been synthesized via a method involving ex0 nucleophilic attack of the stabilized enolate (41) on the (q6-arene)tricarbonylchromium complex of the hydronaphthalene derivative (42).& The thienamycin precursor (43) has been prepared with the key step involving insertion of (-)-PhCH( Me)NH2 into the .Ir-allyltricarbonyliron complex (44) in the presence of ZnCl,.TMEDA to give diastereoisomeric lactone complexes (45) and (46) in 60% yield.47 The separated CN Me II 45 H. Brunner and B. Hammer Angew. Chem. Int. Ed. Engl. 1984 23 312. 46 M. Uernura T. Minarni and Y. Hayashi 1.Chem. Soc. Chem. Commun. 1984 1193. 47 S. T. Hodgson D. M.Hollinshead and S. V. Ley J. Chem. Soc.Chem. Commun. 1984,494. 218 D. Parker lactam (45) was oxidized with Ce’” to give the p-lactam (47) which may be readily transformed into (43). Nucleophilic attack on the ex0 isomer of the chiral allylmolyb- denum complex [R(CO)( NO)MoL]+ (R = neomenthylcyclopentadienyl L = 7’-cyclo-octenyl) has provided a simple route to enantiomerically pure allylically substituted alkenes e.g. (48) The configuration at the metal centre controls the configuration at the generated chiral allylic centre owing to preferential attack cis to the NO ligand in the ex0 i~omer.~~.~’ An enantiospecific synthesis of (+)-gabaculine (49) involves amination of the resolved q4-dienetricarbonyliron com- plex (50)” (Scheme 9). Various new organoiron synthons have been developed51i52 including some vinyl ether iron complexes as vinyl cation equivalents.Reaction of (51) with the lithium enolate (52) generates the a-methylene lactone (53).52 R = neomenthylcyclopentadienyl W L = ~3-cyclooctenyl C0,Me i. Ph3C+ ii. H,N-C0,Bu‘ Hunig’s base (CO),Fe -6 (48) C0,Me 1,0)&--6H i. Me,NO ii. -OH/MeOH ~ iii. H30+ CO,Me& (50) NHC0,Bu‘ (49) NH Scheme 9 Nickel(I1) complexes have been used to catalyse the synthesis qf conjugated dienes from various 5-ring aromatic heterocycles,s3 and amination of but-2-yne in the presence of (Et,NH),NiBr under a CO atmosphere generates the unsaturated 48 J. W. Faller K. H. Chao and H. H. Murray Organometaffics 1984 3 1231. 49 J. W. Faller and K. H. Chao Organometallics 1984 3 927. 5o R.B. M. Bandara A. J. Birch and L. F. Kelly J. Org. Chem. 1984 49 2496. 51 M. Marsi and M. Rosenblum J. Am. Chem. SOC. 1984 106 7264. 52 T. C. T. Chang and M. Rosenblum Isr. J. Chem. 1984 24 99. 53 E. Wenkert H. M. Leftin and E. L. Michelotti J. Chem. SOC.,Chem. Commun. 1984 617. 219 Organometallic Chemistry -Part (i) The Transition Elements lactone (54) in 91% yield.’4 In an interesting application of porphyrin complexes N-substituted aziridines e.g. (55) are formed stereospecifically by reaction of PhI=NR (R = OTs) with stilbene in the presence of iron(Ir1) or manganese TPP.” The nature and synthetic utility of nucleophilic attack on q3-allylpalladium complexes continues to be explored. Using a chiral ?r-allyl (56) it was found that attack by malonates and amines proceeded with inoersion of configuration with the nucleophile attacking the ?r-ally1 directly from the side opposite the metal.With Grignard reagents as nucleophiles retention of configuration occurred with the ?r-ally1 being attacked from the same side as the palladium in a two-step proce~s.’~ Such experiments neatly confirmed the stereochemical course of these two generally accepted reaction pathways. In a separate study the mechanism of the palladium- assisted olefin animation was examined with the reaction sequence varying with the nature of the amine.” Efficient intramolecular chirality-transfer has been observed in reactions of E and 2 ally1 carbonates using Pdo catalysts with phosphine or phosphite ligands.” Thus cyclization of (57) in the presence of a phosphine- palladium complex stereoselectively generated the chiral lactone (58).The synthesis of various bicyclic and tricyclic 7-oxaprostaglandin endoperoxide analogues has been devised uia oxypalladation of norbornadiene. Alkoxylation of dichloro(norbor- nadiene)palladium with OH(CH2)5C02B~‘,followed by in situ hydroformylation gave (59).59 The stereoselective palladium-catalysed 1 ,Cdiacetoxylation of 1,3-dienes 0 0),,C02Me Pd,(dba),.CHCI Me0,CO A H m 5 C0,Me (58) (57) (59) 54 H. Hoberg and J. F. Fananas J. Organomet. Chem. 1984 262 C24. 55 D. Mansuy J.-P. Mahy A. Dureault G. Bedi and P. Battioni J. Chem. SOC.,Chem. Commun. 1984 1161. 56 T. Hayashi M. Konishi and M. Kumada J. Chem. SOC.,Chem Commun.1984 107. 57 L. S. Hegedus B. Altermark K. Zetterberg and L. F. Olsson 1. Am Chem Soc. 1984 106 7122. 58 T. Takahashi Y. Jinbo K. Kitamura and J. Tsuji Tetrahedron Left. 1984 25 5921. 59 R. C. Larock and D.R. Loach 1. Org. Chem. 1984.49. 2144. 220 D. Parker permits the synthesis of 1,4-diacetoxy-2-alkenes under ambient conditions,6' and this route has been applied to the preparation of a key intermediate in the synthesis of racemic shikimic acid.6l A palladium-promoted synthesis of 5-dialkylamino-1,3-pentadienes (as found in the antibiotic griseoviridin) has also been described (Scheme - -/ 0 It LiCI/LiOAc C1 P(OEt),/Nal P(OEt) Pd(OAc),/HOAc ' AcO-R,NH/Pd(PPh,)4+ R,N i. ~NP~JTHF ii. R'CHO Scheme 10 4 Use of Metal Carbenes The potential of Fischer carbene complexes as olefinating agents has long been realised but despite the earlier work on tantalum ~arbenes~~ and the introduction of the Tebbe developments have been surprisingly slow.A series of papers however has described tandem and concurrent cycloaddition-annulation reactions of chromium alkynyl carbene The Diels-Alder reaction of a,P -acetylenic chromium carbene complexes (60) with dienes proceeds smoothly at 20°C and the resultant carbenes are of high synthetic value by virtue of their annulation reactions with alkynes to give the chromium complexed phenols (R2 = H) or cyclohexadienones (R2= Me) (Scheme 11). The cycloaddition and annula- tion reactions may also be carried out concurrently with the carbene complex the diene and the alkyne in one pot.The concurrent reaction (Scheme 12) of (61) (2-trimethylsi1oxy)butadiene and the alkyne (62) gives after ketalization the phenol (63) which is a key intermediate in the synthesis of the anti-tumour agent daunomy- cinone. Carbonyl olefinations may be carried out in protic media using methyl- enemolybdenum reagents such as (64). Aldehydes are selectively olefinated over ketones and the reagent is clearly of value for hydrophilic substrates.68 Some control of olefination stereochemistry has been achieved with long-chain zirconium alkylidene analogues of the Tebbe reagent such as (65).69The photolysis of chromium carbenes with azobenzenes gives rise to azo-metathetical products ;photo-lysis of azobenzene with (66) gives rise to monomeric (67) and dimeric products 60 J.E. Baeckvall J. Vaagberg and R. E. Nordberg Tetrahedron Lett. 1984 25 2717. 61 J. E. Baeckvall E. S. Bystroem and R. E. Nordberg J. Org. Chem. 1984,49 4619. M. Nikaido R.Aslanian F. Scavo P. Helquist B. Aakermark and J. E. Baeckvall J. Org. Chem. 1984 49 4738. 63 R. R. Schrock J. Am. Chem. SOC.,1976,98 5399. 64 F. N. Tebbe G. W. Parshall and G. S. Reddy J. Am. Chem. SOC., 1978 100 3611. 65 W. D. Wulff and C. D. Jung J. Am. Chem. SOC.,1984 106 7565. 66 W. D. Wulff and P. C. Tang J. Am. Chem. SOC.,1984 106 434. 67 W. D. Wulff and P. C. Tang J. Am. Chem. SOC.,1984 106 1132. T. Kauffmann P. Fiegenbaum and R. Wieschdlek Angew. Chem. In?.Ed. Engl. 1984 23 531.69 S. M. Clift and J. Schwartz J. Am. Chem. Soc. 1984 106 8300. Organometallic Chemistry -Part (i) The Transition Efements 221 (C0),Cr<OMe*R2 + R1f -+ ~1% /cr(CO)5 (60) OMe R2=$c-cH 1 RC=CHR2 = Me 1 OH Scheme I1 Ill Me3S10h + @ 1. 0 (62) OMe k <OH ,Me,SiCI ' OH (63) Scheme 12 0 II CIMo=CH LCP2Zr-IR L = PPh, R = But (64) (65) (68) and (69)." Rh,(OAc) has been used to catalyse cyclization of a-diazoketones derived from 3-arylpropanoic acids for the synthesis of bicyclo[5.3.0]decatrienones and tetra lone^.^^ Thus reaction of (70) proceeds to give the trienone (71) in 99% yield at 40 "C. 70 L. S. Hegedus and A. Kramer Organornetailics 1984 3 1263. 71 A. M. McKervey S. M.Tuladhar and F. M. Twohig 1. Chem. SOC.,Chern. Cornrnun. 1984. 129. 222 D. Parker Me PhNf -OMe PhCH,CH,COCHN J-NPh 0 The asymmetric cylopropanation of styrene with 2-diazodimedone (72) is cata- lysed by copper complexes of 3-trifluoroacetyl-( +)-camphor and an immobilized analogue on silica to give product (73) with high enantiomeric purity." 5 Oxidation and Reduction The synthetic application of catalytic homogeneous hydrogenation and oxidation has been a major triumph for organotransition metal chemistry over the past decade. Further progress has been made in the stereoselective hydrogenation of cyclic and acyclic olefinic alcohols. Using Crabtree's cationic iridium complex [Ir(COD)py.( PCy3)]+PF, or the Schrock and Osborn cationic rhodium diene [Rh(nbd)Ph,P(CH,),PPh,]+ the hydroxy-group directs the stereochemical course of the hydrogenation of various allylic alcohols.Reduction of (74) using the rhodium catalyst gives (75) with 2290 :1 diastereo~electivity,'~while the related methyl- enecyclohexanol (76) may be reduced using the same catalyst with 398% selectivity go Me6 Me,.J 0Ph (73) (74) (75) Q""' oMe OH OH (76) (77) in aprotic solvents to give the alcohol (77).74 In the latter case the axial hydroxy- group binds to the rhodium preferentially stabilizing formation of the shown transition-state (78). Such diastereoselective reductions are apparently sensitive to the catalyst to substrate stoicheiometry and the reduction of acyclic olefinic alcohols generally proceeds with lower ~electivity.'~ The mechanism of homogeneous hydro- gentation continues to arouse debate and interest.'H and "P magnetization transfer experiments have suggested a cis (PPh3),Rh arrangement during the course of alkene 72 S. A. Math W. J. Lough L. Chan D. M. H. Abram and 2.Zhou J. Chem. Soc. Chem. Commun. 1984 1038. l3 D.A. Evans and M. M. Morrissey Tetrahedron Lett. 1984 25 4637. 74 J. M. Brown and S. A. Hall Tetrahedron Lett. 1984 25 1393. 75 D. A. Evans and M. M. Momssey J. Am. Chem. Soc. 1984 106 3866. Organometallic Chemistry -Part (i) The Transition Elements hydrogenation using RhC1( PPh3)3 rather than the putative trans arrangement previously accepted.76 Further information pertinent to Sharpless' asymmetric epoxidation procedure has been divulged.Two new catalysts have been reported using Ti(OPri)4 with chiral tartramides the epoxidation of allylic alcohols with Me3C02H gives chiral epoxides with the opposite enantioselectivity from that reported using standard diester tartrates ;using TiCl,(OPr') instead of Ti( OPr'), chlorodiols are produced consistent with regiospecific opening of the intermediate epoxy alcohols.77 The crystal structures of two titanium tartrate asymmetric epoxidation catalysts have been determined (79) and (80).78 The catalysts have a dinuclear structure with the tartrate oxygens bridging the two titanium atoms to form a Ti202 rhombus. In (79) the weak co-ordination of the amide carbonyl oxygens implies facile dissociation and reco-ordination in solution.This feature may facilitate exchange of the alkoxide ligands for the substrate molecules Me3C02H and allylic alcohol via an intermedi- ate in which one or both titanium atoms are pentaco-ordinate. The Sharpless catalyst has been used for the asymmetric oxidation of aryl alkyl sulphides (81) to give Ti (OPr),/ Me,CO,H S . Ar/ 'R HO..JCO E I R = Me Pr Bu Ar = Np Ph the chiral sulphoxides (82) in up to 95% enantiomeric purity. Optimal results were obtained with R = Me in the prochiral sulphide (81) and operating with a closely defined water content at -20 0C.79 The stereochemical course of the osmium tetroxide oxidation of allylic alcohols has been examined in detail and it was found that the relative stereochemistry between the pre-existing hydroxy- or alkoxy-group and the adjacent newly introduced hydroxy-group of the major product is erythro in all cases.8o Alkenes may be epoxidized by iodosylbenzene in the presence of Cu2+ in organic solvents such as acetonitrile.Contrary to some previous suppositions it is apparent that porphyrin ligands are not required for the metal-ion activation of iodosylbenzene.*' 76 A. R. Lucy and J. M. Brown J. Chem. SOC.,Chem. Commun. 1984,914. 71 L. D. Lu R. A. Johnson M. G. Finn and K. B. Sharpless J. Org. Chem. 1984,49 728. 78 I. D. Williams S. F. Pedersen K. B. Sharpless and S. J. Lippard J. Am. Chem. Soc. 1984 106 6430. 79 H. B. Kagan and P. Pitchen Tetrahedron Lett. 1984 25 1049. 80 J. K. Cha W. J. Christ and Y.Kishi Tetrahedron 1984,40 2247. C. C. Franklin R. B. Van Atta A. Fan Tai and J. S. Valentine J. Am. Chem. Soc. 1984 106. 814. 224 D. Parker 6 Other Cycloadditions Isomerizations Carbonylations and Carboxylations In a further development of cobalt-catalysed cycloadditions an intramolecular [2 + 2 + 21 cycloaddition of linear enediynes has been reported in the presence of C~CO(CO)~.~~ Cyclization of (83) for example leads to formation of the tricyclic ring (84). Thermal non-catalysed [6 + 21 cycloadditions are symmetry forbidden (CH2L-2 H2C=CH(CH2),CrCCH2XCH2CECR x@ (83) X = O,CH,CH cpco R = SiMe R (84) but in the presence of TiCl4-Et2A1Cl or ( ~6-C6H6)Ti"(AlC14)2 the reaction proceeds to give mainly the bicyclic diene,83 (Scheme 13).The reaction of cycloheptatriene with dienes and alkynes is presumably facilitated by co-ordination of the triene and modification of its HOMO.Low-valent titanium (TiC13 Zn-Cu) also catalyses the retro-Diels-Alder reaction converting 1,4-endoperoxides into the corresponding 78% 8 Yo 5 yo Scheme 13 1,3-dienes in moderate yield.84 Copper( I) catalysts are useful for [2 + 21 photocyclo- additions and have been used to catalyse the [2 + 21 addition of alkenes with conjugated dienes," and also have facilitated the synthesis of bicyclic pyrrolidines via photobicyclization of ethyl N,N'-diallylcarbonates,86 (Scheme 14). Scheme 14 82 E. D. Sternberg and K.P. C. Vollhardt 1. Org. Chem. 1984 49 1564. 83 K. Mach H. Anttopiusova L. Petrusova V.Hanus and F. Turecek Tetrahedron 1984 40,3295. 84 R. Riguera E. Quinoa and L. Castedo J. Chem. SOC. Chem. Commun. 1984 1120. 85 K. Avasthi S. R. Raychaudhun and R. G. Salomon 1. Org. Chem. 1984 49 4322. 86 R. G. Salomon S. Ghosh S. R. Raychaudhun and T. S. Miranti Tetrahedron Lett. 1984. 25 3167. Organometallic Chemistry -Part (i) The Transition Elements An important step forward in asymmetric catalysis has been the report of the highly enantioselective preparation of chiral E-enamines by isomerization of pro- chiral allylamines catalysed by a chiral rhodium biphosphine comple~.~~-~~ Using the cationic complex (85) isomerization of (86) gives (87) in 100°/~ yield with at least 96% enantiomeric purity. The catalyst is stable for more than 7000 turnovers over a range of reaction temperatures and is tolerant of other functionalities including hydroxyl.The system thus presents a convenient and practical route to chiral aldehydes. For example the catalysed isomerization of (88) gives (+)-7-hydroxydihydrocitronellal,(89) following hydrolysis of the intermediate enamine. Compound (89) is responsible for the fragrance odour of lily of the valley. i. (85) F +HO ii. H,O+ The palladium( 11)-catalysed concurrent decarboxylation-decarbonylation of ally- lic carbones yields P,y-unsaturated esters in good yields” and the total synthesis of the tricyclic hetereocycle (90) involves a palladium-catalysed intramolecular carbonylationof the intermediate (91)?‘ The PdC1,-catalysed intramolecular alkoxy- palladation-carbonylation of the chiral alcohol (92) gives the cis-pyran (93) in high yield and high dia~tereoselectivity.~~ a-Lactams such as (94) may be converted into 87 K.Toni T. Yamagata S. Akutagawa H. Kumobayashi T. Taketomi H. Takaya A. Miyashita R. Nayori and S. Otsuka J. Am. Chem. Soc. 1984 106 5208. 88 S. Otsuka Fund. Res. Homog. Catal. 1984 4 145. 89 H. J. Hansen and R. Schmid Eur. Pat. Appl. EP 104 375; Chem Abstr. 1984 101 111196. 90 J. Tsuji K. Sato and H. Oknmoto J. Org. Chem. 1984 49 1341. 91 M. Mori M. Ishikura T. Ikeda and Y. Bou Heterocycles 1984 22 253. 92 M. F. Semmelhack and C. Bodurow J. Am. Chem. SOC.,1984 106 1496. 226 D. Parker azetidine-2,4-diones (95),by reaction with CO and Rh2C12(CO)4.93 Finally nickel(o) diene complexes catalyse the carboxylation of alkynes and 1,3-dienes to give a$? -unsaturated acids and a,o-diacids H CH,Ph 1 Me0 Hoq,-& CHMe Me0 0 (90) Me O C H CO H (93) 0 (94) (95) 93 D.Roberto and H. Alper Organornetallics 1984 3 1767. 94 H. Hoberg D. Schaefer,G. Durkhart,C. Krueger and M. J. Romas J. Organornet. Chern. 1984,266,203. 95 H. Hoberg and B. Apotecher J. Organornet. Chern. 1984 270 C15.

 



返 回