A Formal [3 + 3] Cycloaddition Reaction. 5. An Enantioselective Intramolecular Formal Aza-[3 + 3] Cycloaddition Reaction Promoted by Chiral Amine Salts
摘要:
A detailed account on chiral secondary amine salt promoted enantioselective intramolecular formal aza-[3 + 3] cycloadditions is described here for the first time. The dependence of enantioselectivity on the structural feature of these chiral amines is thoroughly investigated. This study also reveals a very interesting reversal of the stereochemistry in the respective cycloadducts obtained using C-1- and C-2-symmetric amine salts. In addition, the influence of solvents, counteranions, and temperatures on the enantioselectivity is described, and a unified mechanistic model based on experimental results as well as semiempirical calculations is proposed.
New members of the chiral pool: β-Hydroxypiperidine carboxylates from Baker's yeast reductions of the corresponding keto-esters
作者:David W. Knight、Neil Lewis、Andrew C. Share、David Haigh
DOI:10.1016/s0957-4166(00)80164-0
日期:1993.4
Baker's yeast reduction of the keto-piperidinecarboxylates 2 and 6 leads to the corresponding hydroxy-esters 3 and 7a in good chemical yields and with >99% d.e. and >93% e.e. in both cases.