ONE POT PREPARATION OF PYRIDO[2,3,4-DE]QUINAZOLINES AND BENZO[DE][1,6]NAPHTHYRIDINES BY A CONSECUTIVE PROCESS INVOLVING AN AZA-WITTIG ELECTROCYCLIC RING-CLOSURE HETEROCUMULENE-MEDIATED ANNELATION OR INTRAMOLECULAR DIELS-ALDER CYCLOADDITION SEQUENCE

Aza Wittig-type reaction of bis(iminophosphorane) 1 with one mole of isocyanate leads to the iminophosphoranes 5 which by treatment with a second mole of isocyanate afforded pyrido[2,3,4-de]quinazolines 6. Similarly, reaction with ketenes leads to the formation of benzo[de][1,6]naphthyridines 9. Direct conversion 1 --> 6 and 1 --> 9 were achieved using two moles of isocyanate or ketene respectively.