α-Acyloxynitroso dienophiles in [4+2] hetero Diels–Alder cycloadditions: mechanistic insights
作者:Géraldine Calvet、Susannah C. Coote、Nicolas Blanchard、Cyrille Kouklovsky
DOI:10.1016/j.tet.2010.02.065
日期:2010.4
alpha-Acyloxynitroso derivatives are a class of heterodienophiles leading to valuable 3,6-dihydro-1,2-oxazines or the corresponding aminoalcohols in good yields. The discovery that a beta-oxygenated moiety led to a domino [4+2] cycloaddition/sigma(N-O) bond cleavage in the presence of a catalytic amount of Lewis acid was investigated in detail, through kinetic profiling of the reaction both in the absence and presence of a promoter. These studies showed that the role of the Lewis acid was to accelerate the sigma(N-O) bond cleavage thereby promoting a highly reproducible sequence. In addition, our preliminary results on an asymmetric version of this domino sequence are reported. (C) 2010 Elsevier Ltd. All rights reserved.