The synthesis of substituted 2-aryl 4(3H)-quinazolinones using NaHSO3/DMA.Steric effect upon the cyclisation-dehydrogenation step

A number of 2-aryl substituted 6-pyrrolidino-4(3H)-quinazolinones a re repo rted. They were synthesised in four steps starting from commercially availa ble 5-chloro-2-nitrobenzoic acid. The key cyclisation-dehydrogenation step between 2-amino-pyrrolidinobenzamide 5 and different benzaldehydes employs NaHSO3 as the dehydrogenating agent in hot DMA. This last reaction shows a strong dependence on the position of the substituent at the aromatic ring o f the benzaldehyde used. Thus, the 2-substituted benzaldehydes, in contrast to 3- and 4-substituted compounds give a poor yield of desired products or a mixture.