Stereoelectronic Effect for the Selectivity in C-H Insertion of Alkylidene Carbenes and Its Application to the Synthesis of Platensimycin

摘要

The insertion of alkylidene carbenes into C-H bonds is a powerful synthetic tool for constructing stereochemically defined quaternary carbon centers. Various forms of alkylidene carbene species, including 1-4, have been studied for their reactivity and employed in natural product syntheses. In general, the C-H bonds become more reactive toward carbene insertion if an oxygen atom is directly connected to the reacting C-H bond. However, how the oxygen atom activates the C-H bonds toward insertion or how much it contributes to the reactivity of the C-H bonds in 2 and 3 relative to that in 1 has not been elucidated.