Photochemical preparation of cyclopropanes from cyclobutanones

Abstract

A general method for the preparation of cyclopropanes is reported. Triplet-photosensitized reactions of a series of cyclobutanones give cyclopropanes as the major product. Part 1 describes the synthesis of substituted cyclobutanones used in this study. In Part 2, the photo-reactions of cyclobutanones are reported. Triplet-sensitized reactions of cyclobutanones using acetone as a sensitizer give cyclopropanes as the major non-polar products. The extent of photodecarbonylation seems to be dependent on α-substitution. Electron-donating groups promote decarbonylation while electron-withdrawing groups favour cycloelimination.Key words: photodecarbonylation, cyclobutanones, cyclopropanes, triplet-sensitization.