thus obtainable only as a chloroform solution with 2-4% of (2) and 10-15% of tert-butyl alcohol.Although the hydrocarbon (1) is a highly reactive compound, which polymerizes in condensed phase even at -78"C, its solution in chloroform containing a small amount of hydroquinone can be kept several days at -30 "C. Its spectroscopic resemble those of cyclopropane and cyclopropene. In particular the I3C-H spin-spin coupling constants (158 and 225 Hz) compared to the coupling constants observed for cyclopropane and 3,3-dimethylcyclopropene (respectively 161 and 220 Hz)@I, suggest no difference in the states of hybridization of the corresponding C-H bonds. This would indicate that (1) is a normal spiro compound, and that the interaction between the cyclopropane Walsh orbitals and the cyclopropene m orbitals (pseu-doconj~gation)~'~, if at all present, is not important. Confirmation by UV and PE spectroscopy has so far been precluded by the impurities present in (I).The high strain of (1) is revealed by its unusual chemical reactivity compared with that of 3,3-disubstituted cyclopropenes. As expected, the cyclopropene double bond is very

No abstract

The asymmetric epoxidation of several chalcones and other electron-poor olefins, in the presence of catalytic amounts of poly-(S)-amino-acids in a triphase system with optical yields of up to 96% is described. The influence of the molecular structure of the catalysts and substrates, the solvent, and the temperature on the stereochemistry is discussed.

Thirteen N,N‐diazolylmethanes, including derivatives of pyrazole, imidazole, 1,2,4‐triazole, benzimidazole and indazole were prepared by reaction of azoles with methylene chloride under phase transfer catalysis conditions. The relative amounts of isomeric mixtures obtained with ‘asymmetric’ azoles or with equimolar mixtures of azoles are compared with literature results on monoalkylation of azoles. Proton and carbon‐13 nmr spectra of the N,N'‐diazolylmethanes are discussed.

No abstract