Mendeleev Communications Electronic Version, Issue 1, 1999 (pp. 1–44) Intriguing modes of addition of 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol- 5-ylidene to bicyclopropylidene Armin de Meijere,*a Sergei I. Kozhushkov,a Dmitrii S. Yufitb and Judith A. K. Howardb a Institut für Organische Chemie der Georg-August-Universität Göttingen, D-37077 Göttingen, Germany. Fax: + 49 (0)551 39 9475; e-mail: ameijer1@uni-goettingen.de b Department of Chemistry, University of Durham, DH1 3LE, UK 1,3,4-Triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene 1 reacts with bicyclopropylidene 2 to yield four unexpected products 3–6, none of which resembles the typical [2+1] mode of cycloaddition observed for 1 with electron-deficient alkenes.Bicyclopropylidene 2 is a uniquely strained and reactive tetrasubstituted alkene which has been shown to readily add electrophiles including organometallics1 and undergo various cycloadditions2 including [2+1] cycloadditions even of nucleophilic carbenes such as dimethoxycarbene.3 We have now tested the reactivity of 2 towards the stable carbene 1,3,4-triphenyl-4,5- dihydro-1H-1,2,4-triazol-5-ylidene 14 and found four unexpected products 3–6 resembling four unusual modes of addition (Scheme 1).† The structures of all new compounds 3–6 were unequivocally established by X-ray crystal structure analyses (Figure 1).‡ No mechanistic details of these additions and cycloadditions have been proved as yet and even the rationalisation of their formation is difficult except for compounds 3 and 5.Most † Compounds 3–7 were obtained by heating a solution of the heterocycle 14 (183 mg, 0.615 mmol) and bicyclopropylidene 25 (246 mg, 288 ml, 3.075 mmol) in anhydrous toluene (10 ml) at 100 °C under argon for 3 h in a sealed tube.The resulting mixture was concentrated under reduced pressure and chromatographed (3×15 cm column, 40 g of silica gel, CH2Cl2–hexane, 5:1) to give 28 mg (12%) of 5,7,8-triphenyl-5,6,8-triazadispiro[ 2.0.4.3]undeca-6,10-diene 3, 53 mg (23%) of 1,4-diphenyl-2- (1-cyclopropylcyclopropyl)-6,7-benzo-1,3,5-triazepine 4, 37 mg (19%) of 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-one 7 and 60 mg (25%) of the non-separable mixture of 4,5-dihydro-1,3-diphenyl[4,1' :5,1'' ]bis- (spirocyclopropane)[3a-H][1,2,4]triazolo[4,3-a]quinoline 5 and N(3)-[2- (1-cyclopropylcyclopropylcarbonyl)phenyl]-N(1)-phenylbenzamidrazone 6.Their relative ratio was determined from the 1H NMR spectrum of the mixture in comparison to the spectra of the individual compounds obtained by the selection of the crystals in accordance with their shape. For 3: mp 166–168 °C (decomp.) (hexane–ether), Rf 0.57. 1H NMR (250 MHz, CDCl3) d: 0.86–0.97 (m, 1H, cyclopropyl), 1.04–1.12 (m, 1H, cyclopropyl), 1.24–1.26 (m, 1H, cyclopropyl), 1.39–1.46 (m, 1H, cyclopropyl), 2.46 (dt, 1H, CH2, J 19.3 Hz, 2.0 Hz), 3.24 (dt, 1H, CH2, J 19.3 Hz, 2.3 Hz), 5.53 (dt, 1H, =CH, J 6.5 Hz, 2.0 Hz), 5.70 (dt, 1H, =CH, J 6.5 Hz, 2.3 Hz), 6.77–6.83 (m, 1H, Ph), 7.05–7.19 (m, 3H, Ph), 7.23–7.27 (m, 9H, Ph), 7.43–7.47 (m, 2H, Ph). 13C NMR (62.9 MHz, CDCl3) d: 12.79, 14.61, 39.38 (CH2), 125.61, 127.54, 128.15, 128.52, 128.67, 128.75 (2CH), 113.23, 117.93, 125.09, 125.87, 136.28 (CH), 38.96, 94.09, 129.07, 139.02, 142.04, 145.60 (C).HRMS (EI, 70 eV) m/z: 377.1891 [M]+. For 4: mp 136–138 °C (decomp.) (hexane–ether), Rf 0.51. 1H NMR (250 MHz, CDCl3) d: 0.08–0.12 (m, 2H, cyclopropyl), 0.40–0.55 (m, 2H, cyclopropyl), 0.65–0.88 (m, 2H, cyclopropyl), 1.41–1.43 (m, 2H, cyclopropyl), 1.71–1.80 (m, 1H, cyclopropyl), 6.59 (d, 2H, J 8.0 Hz), 6.72 (t, 1H, J 7.8 Hz), 7.02 (t, 2H, J 7.8 Hz), 7.26–7.88 (m, 7H, Ph), 8.04 (dd, 2H, Ph, J 7.2 Hz, 1.8 Hz). 13C NMR (75.5 MHz, 100 °C, C2D2Cl4) d: 2.82, 15.11 (2CH2), 127.70 (4CH), 112.43, 128.57 (2CH), 12.51, 119.84, 126.81, 128.35, 129.33, 129.64, 130.04 (CH), 27.62, 134.52, 137.15, 144.40, 145.56, 159.07, 169.51 (C).HRMS (EI, 70 eV) m/z: 377.1891 [M]+. For 5: Rf 0.40. 1H NMR (250 MHz, CDCl3) d: 0.62–0.66 (m, 4H, cyclopropyl), 0.92–1.02 (m, 4H, cyclopropyl), 5.95 (s, 1H, CH), 6.95– 7.52 (m, 12H, Ph), 7.85 (d, 2H, Ph, J 7.5 Hz). HRMS (EI, 70 eV) m/z: 377.1891 [M]+. For 6: 1H NMR (250 MHz, CDCl3) d: 0.12–0.15 (m, 2H, cyclopropyl), 0.33–0.39 (m, 2H, cyclopropyl), 0.90–0.99 (m, 2H, cyclopropyl), 1.04– 1.10 (m, 2H, cyclopropyl), 1.38–1.46 (m, 1H, cyclopropyl), 6.09 (s, 1H, NH), 6.33 (d, 1H, J 7.5 Hz), 6.90–7.53 (m, 11H, Ph), 8.24 (d, 2H, Ph, J 7.5 Hz, 1.8 Hz), 11.37 (s, 1H, NH).MS (EI, 70 eV) m/z: 395 [M]+. Compound 7 is known,4 Rf 0.23. probably, the nucleophilic carbene 14 first attacks the double bond in 2 to give the 1,3-zwitterion 8 which may be in an equilibrium with the ring-closed form, the dispiro[2.0.2.1]- heptane derivative 11.For some reason, possibly due to considerable ring strain inherent in the sterically congested skeleton, 11 must be unstable under the employed conditions (100 °C)§ and prefer to open the central ring either back to 8 or with the reverse polarity to give the 1,3-zwitterion 10. The latter can close a six-membered ring by electrophilic attack of the cationic end on one of the vicinal phenyl groups to give the product 5.The triazaspiro[4.4]octadiene 3 can only arise by ring closure of a 1,5-zwitterion like 9 which must have formed from 8 by opening of the anionic cyclopropyl group going along with a 1,2-hydrogen shift (Scheme 2). The formation of the benzotriazepine derivative 4 is particularly obscure as the connectivity of the atoms is changed on ‡ Crystal data: some details of the single-crystal X-ray experiments for compounds 3–6 and crystal data are given in Table 1.All the data were collected using MoKa radiation (l = 0.71073 Å) on a ‘Nonius KAPPACCD’ and a ‘SMART-CCD’ diffractometers for compounds 3 and 4–6, respectively. The structures were solved by direct methods and refined by full-matrix least-square against F2 with anisotropic displacement parameters for all non-hydrogen atoms.Hydrogen atoms in molecules 3–5 were located in the difference Fourier maps and refined isotropically. For compound 6 the positions of H atoms were calculated. For all compounds the maximum features on the final residual maps do not exceed 0.3 e/Å3. Full lists of bond angles, bons lengths, atomic coordinates and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre (CCDC). For details, see ‘Notice to Authors’, Mendeleev Communications, 1999, Issue 1.Any request to the CCDC for data should quote the full literature citation and the reference number 1135/36. § Essentially the same distribution of products 3–6, yet with lower total yield (47%), was observed when carbene 1 was exposed to bicyclopropylidene 2 in THF solution under a pressure of 10 kbar at 20 °C for 24 h.Under the same conditions, but at ambient pressure, only 7% conversion of 1 to 3–6 was observed. N N N Ph Ph Ph toluene 100 ºC, 3 h N N N Ph Ph Ph N N N Ph Ph N N N Ph Ph HNPh Ph N N O H N N N Ph Ph Ph O 1 2 3 (12%) 4 (23%) 5 (12%) 6 (13%) 7 (19%) Scheme 1Mendeleev Communications Electronic Version, Issue 1, 1999 (pp. 1–44) Table 1 Crystal data for compounds 3–6. 3 4 5 6 Chemical formula C26H23N3 C26H23N3 C26H23N3 C26H25N3O Formula weight 377.47 377.47 377.47 395.49 T/K 100 150 120 150 Crystal system monoclinic triclinic triclinic monoclinic Space group P21/n P1 P1 P21 /c Z 4 2 2 4 a/Å 14.607(2) 9.583(1) 8.870(1) 10.715(1) b/Å 9.031(1) 10.053(1) 10.509(1) 19.578(1) c/Å 15.936(2) 12.805(1) 11.889(1) 10.415(1) a/° 90 98.12(1) 78.24(1) 90 b/° 110.05(1) 105.96(1) 70.70(1) 105.43(1) g/° 90 116.99(1) 72.67(1) 90 V/Å3 1974.9(5) 1004.6(1) 991.6(1) 2106.2(1) Dc/g cm–3 1.270 1.248 1.264 1.247 m/mm–1 0.075 0.074 0.075 0.077 Reflections measured 7471 8406 9014 11941 Unique reflections 3872 5241 4506 2748 R1 (I = 2s) 0.0575 0.0553 0.0863 0.0973 wR2 0.1654 0.1305 0.2299 0.1643 GOOF 0.990 1.076 0.972 1.196 3 4 5 6 C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) Figure 1 Structures of compounds 3–6 in the crystals.N(1) N(2) N(3) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) N(1) N(2) N(3) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) N(1) N(2) N(3) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) N(1) N(2) N(3) O(1) N N N Ph Ph Ph N N N Ph Ph Ph N N N Ph Ph 1 2 Scheme 2 N N N Ph Ph Ph 8 N N N Ph Ph Ph 9 10 N N N Ph Ph Ph 11 3Mendeleev Communications Electronic Version, Issue 1, 1999 (pp. 1–44) going from 8 or 10 to 4.Formally, this could be brought about by opening of the five-membered heterocycle in 10 between the two adjacent nitrogens, a subsequent 1,3-shift of a phenyl group from the central to the terminal nitrogen and ring closure by intramolecular nucleophilic aromatic substitution.Similarly difficult to explain is the formation of compound 6. Formally, an intramolecular electrophilically assisted nucleophilic aromatic substitution in 10 could lead to a tricyclic benzazepine derivative which due to its ring strain might undergo hydrolysis to give 6 during column chromatography.Without any further evidence, all these mechanistic considerations, especially the last ones, are highly speculative. None the less, the observed reactivity of the stable carbene 1, which so far has been reported to react only with acceptor-activated C=C double bonds,4 towards the strained tetrasubstituted alkene 2 is quite remarkable, and so are the products 3–6.This work was supported by the Fonds der Chemischen Industrie, and the Engineering and Physical Science Research Council (EPSRC, UK). We are grateful to the companies BASF AG, Bayer AG and Hüls AG for generous gifts of chemicals, to Dipl.-Chem. R. Machinek for recording the high-temperature 13C NMR spectra and to Dr.B. Knieriem for his careful reading of the manuscript. We are very thankful to Dr. J. Steed (Imperial College, London) for the opportunity to use the Nonius KAPPACCD X-ray diffractometer and for valuable help in processing of the collected data. References 1 S. Braese and A. de Meijere, Angew. Chem., 1995, 107, 2741 (Angew. Chem., Int. Ed. Engl., 1995, 34, 2545) and references cited therein. 2 A. de Meijere, S. I. Kozhushkov and A. F. Khlebnikov, Zh. Org. Khim., 1996, 32, 1607 (Russ J. Org. Chem., 1996, 32, 1555). 3 A. de Meijere, S. I. Kozhushkov, D. S. Yufit, R. Boese, T. Haumann, D. L. Pole, P. K. Sharma and J. Warkentin, Liebigs Ann. Chem., 1996, 601. 4 D. Enders, K. Breuer, J. Runsink and J. H. Teles, Liebigs Ann. Chem., 1996, 2019. 5 A. de Meijere, S. I. Kozhushkov, T. Spaeth and N. S. Zefirov, J. Org. Chem., 1993, 58, 502. Received: Cambridge, 26th October 1998 Moscow, 11th November 1998; Com. 8/08251K