Copper-Catalyzed Divergent Addition Reactions of Enoldiazoacetamides with Nitrones
摘要:
Catalyst-controlled divergent addition reactions of enoldiazoacetamides with nitrones have been developed. By using copper(I) tetrafluoroborate/bisoxazoline complex as the catalyst, a [3+3]-cycloaddition reaction was achieved with excellent yield and enantioselectivity under exceptionally mild conditions, which represents the first highly enantioselective base-metal-catalyzed vinyl-carbene transformation. When the catalyst was changed to copper(I) triflate, Mannich addition products were formed in high yields with near exclusivity under otherwise identical conditions.
Highly Regio- and Stereoselective Dirhodium Vinylcarbene Induced Nitrone Cycloaddition with Subsequent Cascade Carbenoid Aromatic Cycloaddition/NO Cleavage and Rearrangement
作者:Xiaochen Wang、Quentin M. Abrahams、Peter Y. Zavalij、Michael P. Doyle
DOI:10.1002/anie.201201917
日期:2012.6.11
An abnormal cascadeprocess provides a selective method for the preparation of tricyclic heterocycles. The cascade involves a metal carbene induced regioselective [3+2] cycloaddition, a Buchner reaction, and a [1,7]‐oxygen migration, which occurs with NO cleavage (see scheme). The products are formed with remarkable specificity.
Herein, we report a novel strategy for the regioselectivesynthesis of aromatic and heteroaromatic 2,3-dihydrooxazoles from 2-alkynyl-1,3-dithianes and nitrones. This method exploits the 1,3-dithiane umpolung, nucleophilic cycloaddition, and rearrangement processes to achieve the rapid assembly of dihydrooxazole molecules. The regioselective method is extremely mild, achieving complete conversion within