Palladium-catalyzed intramolecular enantioselective C(sp3)-H insertion of donor/donor carbenes

摘要

Herein, the first palladium-catalyzed intramolecular enantioselective C(sp(3))-H insertion reaction of donor-donor carbenes has been successfully achieved. This facile protocol enables the rapid construction of a collection of enantioenriched decorated indolines with two contiguous stereocenters in a single step. Both enynones and diazo compounds are efficient donor-donor carbene precursors for this reaction. By an adjustment of ligands and protecting groups of the substrates, the palladium-carbene intermediates from diazo compounds afford sparse trans-indolines with excellent enantioselectivities, while carbenes from enynones deliver cis-indolines exclusively. Based on the control reactions and Hammett analysis, a stepwise Mannich-type pathway through a short-lived and compact zwitterionic intermediate is proposed.

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