An intramolecular hetero Diels–Alder reaction of α-(alkynylsiloxy)aldimine derivatives

Intramolecular hetero Diels–Alder reactions of α-(alkynylsiloxy)aldimine derivatives were developed. α-(Alkynylsiloxy)aldehydes, which were prepared from 1,2-alkanediols in two steps, were converted into the corresponding biscarbamates or N-arylimines. In the presence of BF3·OEt2, the biscarbamates afforded oxazine derivatives in high diastereoselectivity. On the other hand, quinoline derivatives were obtained in good yields by treating the N-arylimines with trifluoromethanesulfonic acid.