1,2-Migration in rhodium(II) carbene transfer reaction: Remarkable steric effect on migratory aptitude

A series of diazo carbonyl compounds bearing different substituents have been prepared in order to investigate the steric effect in 1,2-migration reaction of rhodium(II) carbene. Through the investigation on the diazo decomposition of these compounds with Rh-2(OAc)(4), it was found that the steric effect could dramatically influence the migratory aptitude. In many cases, the steric effect could override the inherent electronic effect of the substituent.