- Nickel-Catalyzed Arylation of C(sp3)-O Bonds in Allylic Alkyl Ethers with Organoboron Compounds
A nickel-catalyzed cross-coupling of allylic alkyl ethers with organoboron compounds through the cleavage of the inert C(sp3)-O(alkyl) bonds is described. Several types of allylic alkyl ethers can be coupled with various boronic acids or their derivatives to give the corresponding products in good to excellent yields with wide functional group tolerance and excellent regioselectivity. The gram-scale reaction and late-stage modification of biologically active compounds further prove the practicality of this synthetic method.
- Li, Xiaowei,Li, Yuxiu,Zhang, Zhong,Shi, Xiaolin,Liu, Ruihua,Wang, Zemin,Li, Xiangqian,Shi, Dayong
p. 6612 - 6616
(2021/09/02)
- 1,4-Addition of Triorganozincates and Silyldiorganozincates to α,β-Unsaturated Ketones
Lithium and magnesium triorganozincates, prepared by combination of ZnCl2(TMEDA) with 3 molar equivalents of RLi or RMgX, or from dialkylzinc and 1 molar equivalent of RLi or RMgX, react with 2-cyclohexen-1-one (1) under mild conditions to produce moderate to good yields of the 1,4-addition products 2.The approximate reactivity order obtained from the product distribution using unsymmetrical zincates is tBuCH2 tBu, Me Me2PhSi.The latter groups are transferred with good selectivity from mixed reagents derived from Me2Zn.This sequence differs strikingly from that exhibited by unsymmetrical cuprates which transfer neopentyl very easily, and also tert-butyl more easily than the corresponding zincates.The methylation with Me3ZnLi is catalyzed by cobalt complexes.Other enones (7-13) generally give poor yields, and the cobalt-catalyzed methylation of isophorone (3) is complicated by a Kharasch-type deconjugation.Mixed silyldialkylzincates, Me2PhSiZnR2Li, produce the β-silyl ketones from a variety of unhindered or moderately hindered enones in practically useful yields; one example of an α,β-unsaturated ester (12) is also included.
- Tueckmantel, Werner,Oshima, Koichiro,Nozaki, Hitosi
p. 1581 - 1593
(2007/10/02)