THE KULINKOVICH CYCLOPROPANATION OF CARBOXYLIC ACID DERIVATIVES

摘要

Cyclopropanes are characterized by high ring-strain energy and have been employed as useful building blocks in organic synthesis. The incorporation of a heteroatom donor substituent, such as OH, OR, NR2, or SR, on the ring imparts enhanced reactivity. Hydroxycyclopropanes (cyclopropanols), in particular, have been thoroughly studied due to their facile ring cleavage. Among several known methods, a new method for the preparation of cyclopropanols involves dialkoxytitanacyclopropane-mediated cyclopropanation (the Kulinkovich cyclo-propanation) of esters with a Grignard reagent R~3CH2CH2MgX in the presence of titanium isopropoxide (Eq. 1).