Preparation of Fused Tetracyclic Quinazolinones by Combinations of Aza‐Wittig Methodologies and Cu^I‐Catalysed Heteroarylation Processes

Abstract

Abstract A number of linear quinazolinones fused to five‐membered rings – benzimidazo[2,1‐ b ]quinazolinones 8 and benzothiazolo[2,3‐ b ]quinazolinones 10 – have been prepared from iminophosphoranes 4 , derived from N ‐substituted o ‐azidobenzamides by a combination of the aza‐Wittig methodology and Cu I ‐catalysed heteroarylation. The presence of a nitrogen functionality in the N ‐aryl substituent of 4 promotes heterocyclization after an aza‐Wittig reaction/reductive process, either across the 2‐position, to afford quinazolino[2,1‐ b ]quinazolinones 11 – 14 , or across the 4‐position, to afford the benzimidazo[1,2‐ c ]quinazoline 16 from the initially formed 3 H ‐quinazolin‐4‐one. When an acetyl group is present in the N ‐aryl substituent of 4 , aza‐Wittig reactions with isocyanates lead directly to 4‐methylene‐4 H ‐3,1‐benzoxazines 18 ; this transformation involves the initial formation of a carbodiimide, which undergoes ring‐closure through the enol form of the carboxamide group and eventually an unprecedented iminobenzoxazine/methylenebenzoxazine rearrangement. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)