resumo
The development of general and efficient asymmetric organocatalytic additions of malononitrile and nitromethane to 1,5-diarylpenta-2,4-dien-1-ones (cinnamylideneacetophenones) catalyzed by cinchona organocatalysts is reported. The reactions afforded excellent enantioselectivities (up to 99%), high yields (up to 97%), and exclusive 1,4-addition regioselectivities. The potential of these new enantioselective additions lies in the demonstration that organocatalysts bearing primary amino groups in combination with TFA provide effective catalytic systems for the activation of a broad range of aryl ketones under mild conditions to give compounds with high levels of enantioselectivity and yields.
palavras-chave
ASYMMETRIC CONJUGATE ADDITION; QUATERNARY AMMONIUM-SALTS; PHASE-TRANSFER CATALYSTS; AZA-MICHAEL REACTIONS; ALPHA,BETA-UNSATURATED KETONES; CARBONYL-COMPOUNDS; CYCLIC ENONES; THIOUREA ORGANOCATALYST; BOND DONORS; NITROALKANES
categoria
Chemistry
autores
Oliva, CG; Silva, AMS; Resende, DISP; Paz, FAA; Cavaleiro, JAS
nossos autores
Filipe Alexandre Almeida Paz
Investigador Principalagradecimentos
Thanks are due to the University of Aveiro, to the Fundacao para a Ciencia e a Tecnologia (FCT) and the Fundo Europeu de Desenvolvimento Regional (FEDER) for funding the Organic Chemistry Research Unit and for financial support towards the purchase of a single-crystal diffractometer. The authors are very grateful to Professor Juan Carlos Carretero (Universidad Autonoma de Madrid, Spain) for providing access and information on the use of chiral HPLC columns and also to Dr. Fernando Domingues (Universidade de Aveiro) for his assistance with HPLC determinations. One of us (C. G. O.) thanks the FCT for a