1, 3- Dipolar cycloadditions between diazocompounds and activated olefins or acetylenes have been extensively investigated and are presently well understood but, there has been little work reported on 1, 3-dipolar additions with substituted acroleins. Catalytic synthetic approach to get the highly functionalized pyrazolines was investigated. In the presence of chiral (S)-oxazaborolidinium ion as catalyst, the reaction proceeded with high to excellent enantioselectivities (up to 99 % ee).
Enantioselective cyclopropanation reactions via Michael- initiated ring closure between diazoacetates and alpha,beta-unsaturated aldehydes are highly desirable as the corresponding cyclopropanes containing two or more electron-withdrawing groups can be valuable synthetic intermediates for various applications. In the presence of chiral (S)-oxazaborolidinium cation as catalyst, catalytic synthetic approach to get the highly functionalized cyclopropane was investigated. Reactions proceeded in high yield (up to 93%) with high to excellent diastereoselectivity (up to 98% de) and enantioselectivity (up to 95% ee).