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 pre-activation under a metal-free system.
Department of Frontier Materials, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, 466-8555 (Japan).
Takayuki
T
Nishimine
Department of Frontier Materials, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, 466-8555 (Japan).
Hiromi
H
Taira
Department of Frontier Materials, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, 466-8555 (Japan).
Etsuko
E
Tokunaga
Rigaku Corporation, 3-9-12 Matsubara-cho, Akishima, Tokyo, 196-8666 (Japan).
Motoo
M
Shiro
Department of Frontier Materials, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, 466-8555 (Japan). nozshiba@nitech.ac.jp.
Norio
N
Shibata
C-F activation; fluorine; organocatalysis; silicon; trichloromethylation