Diastereoselective Diels−Alder Reaction of 2-(α,β-Unsaturated)acyl-3-phenyl-l-menthopyrazoles
摘要:
The reaction of 2-(alpha,beta-unsaturated)acyl-3-phenyl-l-menthopyrazoles (9) with dienes gave Diels-Alder adducts in good yield. The addition of MgBr2. OEt2 or ZnCl2 accelerated these reactions through the formation of chelating bonds such as N ... Mg ... O=C or N ... Zn ... O=C. The structural fixation by these catalysts also promoted the endo and diastereoselectivities of the Diels-Alder addition on the Re-face of the dienophiles. These results were supported by PM3 calculations, in which the heats of formation of the transition states anticipated the remarkable differences between the Re- and Si-facial attacks of the dienes.
The reaction of 2-(alpha,beta-unsaturated)acyl-3-phenyl-l-menthopyrazoles (9) with dienes gave Diels-Alder adducts in good yield. The addition of MgBr2. OEt2 or ZnCl2 accelerated these reactions through the formation of chelating bonds such as N ... Mg ... O=C or N ... Zn ... O=C. The structural fixation by these catalysts also promoted the endo and diastereoselectivities of the Diels-Alder addition on the Re-face of the dienophiles. These results were supported by PM3 calculations, in which the heats of formation of the transition states anticipated the remarkable differences between the Re- and Si-facial attacks of the dienes.