Enantioselective [4+2] cycloaddition of ketenes and 9,10-phenanthrenequinone catalyzed by N-heterocyclic carbenes
作者:Pan-Lin Shao、Xiang-Yu Chen、Li-Hui Sun、Song Ye
DOI:10.1016/j.tetlet.2010.02.122
日期:2010.4
Chiral N-heterocycliccarbenes were found to be efficient catalysts for the formal [4+2] cycloaddition reaction of alkyl(aryl)ketenes and 9,10-phenanthrenequinone to give the corresponding cycloadducts in good yields with high enantioselectivities.
Asymmetric Synthesis of Tetrahydrofurans through Palladium(0)-Catalyzed [3 + 2]-Cycloaddition of Vinylcyclopropanes with Ketenes
作者:Mukulesh Mondal、Manashi Panda、Vickie McKee、Nessan J. Kerrigan
DOI:10.1021/acs.joc.9b01854
日期:2019.9.20
In this article we describe a new asymmetric synthesis of highly substituted tetrahydrofurans through a Pd(PPh3)4-catalyzed formal [3 + 2]-cycloaddition of donor–acceptorcyclopropanes and ketenes. The desired structural motif was formed in moderate to excellent yields (42–84% for 16 examples), with excellent Z:E isomer diastereoselectivity (≥19:1 for 16 examples), and with good to excellent enantioselectivity
difluoroenoxysilanes is disclosed for the first time, which enabled the direct construction of versatile gem-difluoroalkenes through an unprecedented highly efficient addition reaction with ketenes. A series of valuable gem-difluoroenol esters were achieved in good to excellent yields. The synthetic versatility of this protocol is further demonstrated by the gram-scale synthesis and good functional group tolerance
An Asymmetric Hetero-Claisen Approach to 3-Alkyl-3-aryloxindoles
作者:Nicolas Duguet、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1021/ol901441t
日期:2009.9.3
The reaction of a chiral N-phenylnitrone derived from Garner's aldehyde with alkylarylketenes generates 3-alkyl-3-aryloxindoles directly in excellent yields and with good to excellent levels of enantioselectivity (up to 90% ee).