摘要:
Photochemical cycloaddition of the enaminecarbaldehydes 15 and 16 with the acrylic acid derivatives 20a-c gave the 2-hydroxytetrahydropyridines 21a-c and 24a-c, respectively which cyclize on treatment with trifluoroacetic acid or Lewis acids to furnish the quinolizidines 22a-c and pyrido[1,2-a]azepines 25a-c, respectively in good yields and with high 1,3-induced diastereoselectivity. Indolizidines 27 cannot be prepared by this method.