Enantioselective Trichloromethylation of MBH-Fluorides with Chloroform Based on Silicon-assisted C-F Activation and Carbanion Exchange Induced by a Ruppert-Prakash Reagent

Enantioselective trichloromethylation of Morita-Baylis- Hillman (MBH)-type allylic fluorides with chloroform (HCCl3) under organocatalysis was achieved with high to excellent enantioselectivities. Silicon-assisted C-F bond activation by a Ruppert-Prakash reagent and direct activation of HCCl3 by a carbanion exchange process with trifluoromethyl (CF3) carbanion generated in situ from the Ruppert-Prakash reagent realized the direct asymmetric trichloromethylation at a stereogenic allylic positon, without any help from transition metal catalysis, and under very mild conditions. Pre-activation of HCCl3 was not required. This method was extended to the direct enantioselective introduction of other C-H compounds such as alkyne, arene, indene, and FBSM without any preactivation under a metal-free system.