TANDEM WOLFF REARRANGEMENT ALPHA-CYCLIZATION OF TERTIARY-AMINES SEQUENCE - SYNTHESIS OF SOME 1H-2-BENZOPYRAN DERIVATIVES

The thermolyses of dimethyl 1-diazo-2-oxo(2-(N,N-disubstituted aminome thyl)phenyl)-ethylphosphonates 6a-e or the related ester 6f afford 1-d isubstituted amino-1H-2-benzopyran derivatives 9a-f through a 3-step s equence involving Wolff rearrangement, [1,5] hydride shift and subsequ ent ring closure. Compounds 9 can be easily transformed into 1-hydroxy -, 1-methoxy- or 1-thiophenoxy-1H-2-benzopyran or isoquinoline derivat ives by the action of various nucleophilic reagents. Extension of the reaction to some heterocyclic diazophosphonates analogous to 6 is also described. (C) 1998 Elsevier Science Ltd. All rights reserved.