Reactivity and synthetic applications of bis(iminophosphoranes). One-pot preparation of pyrido[2,3,4-de]quinazolines and benzo[de][1,6]naphthyridines
摘要:
Aza-Wittig reaction of bis(iminophosphorane) 4 with 2 equiv of isocyanate leads directly to pyrido[2,3,4-de]quinazolines 5. Iminophosphoranes 8, available from 4 and 1 equiv of the appropriate isocyanate, react either with 1 equiv of isocyanate or ketene to give pyrido[2,3,4-de]quinazolines 9 or benzo[de][1,6]naphthyridines 10, respectively. Bis(iminophosphorane) 4 by sequential treatment with aldehydes and isocyanates yielded 2,3-dihydropyrido[2,3,4-de]quinazolines 17.