Abstract
Photolysis of 5-benzyl-2-methoxy-2,5-dimethyl-Δ3-1, 3,4-oxadiazoline and of the 5,5-dibenzyl analogue with 300-nm light afforded 1-phenyl-2-diazopropane and 1,3-diphenyl-2-diazopropane, respectively. The diazoalkanes were intercepted, in situ, with dimethyl acetylenedicarboxylate to afford 3-benzyl-4,5-bis(methoxycarbonyl)-3-methyl-3H-pyrazole and 3,3-dibenzyl-4,5-bis(methoxycarbonyl)-3H-pyrazole, respectively. Those pyrazoles are short-lived under the reaction conditions and undergo two major reactions. Photolysis prior to rearrangement affords the corresponding 3,3-dialkyI-1,2-bis(methoxycarbonyl)-cyclopropenes. Thermal 1,5-benzyl migration converts the two 3H-pyrazoles in part into the corresponding 4H-pyrazoles, which undergo photolysis to 2,3-dialkyl-1,3-bis(methoxycarbonyl)cyclopropenes.
Thermolysis of the 3,3-dialkyl-1,2-bis(methoxycarbonyl) cyclopropenes affords conjugated dienes, presumably through the sequence cyclopropene → vinyl carbene → diene. The stereochemistry of the dienes was determined and a mechanism consistent with that stereochemistry is proposed.
The 2,3-dialkyl-1,3-bis(methoxycarbonyl)cyclopropanes are very stable under conditions that convert isomeric 3,3-dialkyl-1,2-bis(methoxycarbonyl)cyclopropenes to conjugated dienes. It is proposed that the effect of substitution pattern on the thermolysis rate constants is the result of combined ground state and transition state factors.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Wiberg, K. B., and Bartley, W. J.J. Am. Chem. Soc.,1960,82, 6375.
For recent reviews see: (a) Baird, M. S.Top. Curr. Chem.,1988,144, 147;
For recent reviews see: Billups, W. E., Haley, M. M.; Lee, G.-A.Chem. Rev.,1989,89, 1147;
For recent reviews see: Steinmetz, M. G.; Srinivasan, R.; Leigh, W. J.Rev. Chem. Intermed.,1984,5, 57.
York, E. J.; Dittraar, W.; Stevenson, J. R.; Bergman, R. G.J. Am. Chem. Soc.,1973,95, 5680.
Pincock, J. A.; Montsokapas, A. A.Can. J. Chem.,1977,55, 979.
Yoshimine, M.; Pacansky, J.; Honjou, N.J. Am. Chem. Soc.,1989,111, 2795.
Majchrzak, M. W.; Békhazi, M.; Tse-Sheepy, I.; Warkentin, J.J. Org. Chem.,1989,54, 1842.
Hoffmann, R. W.; Luthardt, H.J. Tetrahedron Lett.,1966, 411.
Békhazi, M.; Warkentin, J.J. Org. Chem.,1982,47, 4870;
Békhazi, M.; Warkentin, J.J. Am. Chem. Soc.,1981,103, 2473;
Békhazi, M.; Warkentin, J.J. Am. Chem. Soc.,1983,105, 1289;
Békhazi, M.; Warkentin, J.Can. J. Chem.,1983,61, 619;
Békhazi, M.; Warkentin, J.J. Am. Chem. Soc.,1983,105, 5675.
Butler, R. N.; Scott, F. L.; O'Mahoney, T. A. F.Chem. Rev.,1973,73, 93;
Warkentin,J. Synthesis,1970, 279.
Majchrzak, M. W.; Jefferson, E.; Warkentin, J.J. Am. Chem. Soc.,1990,112, 2449.
Dietrich-Buchecker, C.; Franck-Neumann, M.Tetrahedron,1977,33, 751.
Kapur, S.; Mathur, N. C.; McManus, K.; Pincock, A. L.; Pincock, J. A.;Can. J. Chem.,1988,66, 2888.
Zimmerman, H. E.Acc. Chem. Res.,1972,5, 393.
Padwa, A.; Chou, C. S.; Rosenthal, R. J.; Rubin, B.J. Am. Chem. Soc.,1981,103, 3057.
Calculated by Dr. N. H. Werstiuk, using the AM1 (Austin Model 1) program. Dewar, M. J. S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J. J. P.J. Am. Chem. Soc.,1985,107, 3902.
Brauman, J. I.; Ellis, L. E.; van Tamelen, E. E.J. Am. Chem. Soc.,1966,88, 846.
Closs, G. L.; Böll, W. A.; Heyn, H.; Dev, V.J. Am. Chem. Soc.,1962,90, 173.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Majchrzak, M.W., Warkentin, J. & Woollard, J.M.K.R. Synthesis and thermolysis of tetrasubstituted cyclopropenes. Struct Chem 2, 137–146 (1991). https://doi.org/10.1007/BF00676625
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00676625