The development of highly active acyclic chiral hydrazides for asymmetric iminium ion organocatalysis
作者:Eoin Gould、Tomas Lebl、Alexandra M. Z. Slawin、Mark Reid、Tony Davies、Andrew D. Smith
DOI:10.1039/c3ob41719k
日期:——
Double asymmetric induction has been employed as a tool to optimise pyrazolidinone-derived organocatalysts for the asymmetric iminiumion catalysed Diels–Alder reaction. Mechanistic studies revealed a superior hydrazide catalyst deriving from methanolysis of the chiral pyrazolidinone precursor. This catalyst displays unusually high endo diastereoselectivity and good enantioselectivity with a range
(1<i>R</i>)-(+)-Camphor and Acetone Derived α′-Hydroxy Enones in Asymmetric Diels−Alder Reaction: Catalytic Activation by Lewis and Brønsted Acids, Substrate Scope, Applications in Syntheses, and Mechanistic Studies
作者:Patricia Bañuelos、Jesús M. García、Enrique Gómez-Bengoa、Ada Herrero、José M. Odriozola、Mikel Oiarbide、Claudio Palomo、Jesús Razkin
DOI:10.1021/jo9023039
日期:2010.3.5
enones as reaction partners of the Diels−Alder reaction are shown, with especial focus on their potentials and limitations in solving the above difficult cases. α′-Hydroxy enones are able to bind reversibly to bothLewisacids and Brønsted acids, forming 1,4-coordinated species that are shown to efficiently engage in these inherently difficult Diels−Alder reactions. On these bases, a convenient control