Substrate Structural Effects in Yttrium(III)-Catalyzed Hydroamination/Cyclizations of 1,2-Disubstituted and 1,1,2-Trisubstituted Aminoalkenes Terminated by 2-(Phenyl) and 2-(2-Heteroarenyl) Groups
摘要:
A series of 2-phenyl- and 2-(2-heteroarenyl)-bearing amines possessing 1,2-disubstituted and 1,1,2-trisubststuted alkenes have been evaluated in intramolecular hydroaminations catalyzed by Y[N(TMS)(2)](3) (1(Y)). Aminoalkenes possessing a terminal 2-(5-trimethylsilyl)thienyl group exhibited substantially enhanced reactivity compared to their 2-(phenyl)-containing counterparts. Cyclization efficiencies imparted by the 2-[(5-trimethylsilyl) furanyl] substituent were comparable or only slightly better than those obtained with the simple the 2-(phenyl) group.
作者:Ashok K. Basak、Naoyuki Shimada、William F. Bow、David A. Vicic、Marcus A. Tius
DOI:10.1021/ja103028r
日期:2010.6.23
An organocatalytic asymmetric Nazarov cyclization of diketoesters that proceeds by means of a dual activation mechanism has been developed. Screening of a number of catalysts led to a new thiourea that incorporates a primary amino group. The method gives rise to cyclic products with two adjacent quaternaryasymmetriccarbon atoms, one of which is an all-carbon stereocenter, with complete or nearly
The effect of absorbing resins on the yeast reduction of cl,P-unsaturated carbonyl compounds is reported. Enantioselectivity, chemoselectivity and space-time yields of the biotransformation are impressively enhanced. The distribution of substrates and products between the resin and the water phase shows that the improved selectivity has to be attributed to the control of substrate concentration, (C) 1998 Elsevier Science Ltd. All rights reserved.
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