Synthesis of optically active cyclopropanes by functionalization of cyclopropenes

In this review, the synthesis of optically active cyclopropanes from cyclopropenes, via the formation of C-H, C-C and C-heteroatom bonds, is described. The transformations used to access optically active cyclopropanes can proceed either by enantioselective reactions of racemic cyclopropenes, such as reductions and organometallic additions, or by diastereoselective transformations of optically active cyclopropenes, such as radical additions, cycloadditions, and 3,3-sigmatropic rearrangements. The mechanisms that rationalize the observed stereochemical outcomes are also discussed.