Amides Niementowski quinazoline synthesis

Niementowski quinazoline synthesis. Formation of 4-oxo-3,4-dihydroquinazolines by cycli-zation of the reaction products of anthranilic acid and amides. 

The Niementowski quinazoline synthesis is the condensation of an anthranilic acid (1) with an amide (2) to produce a 4-keto-3,4-dihydro-quinazoline product (3). The reaction occurs under thermal conditions, and reaction temperatures > 100 °C are generally required. This reaction is also often referred to as the Niementowski reaction, and occasionally as the Niementowski 4-quinazolone synthesis or von Niementowski synthesis. ... 

Quinazolin-4(3//)-one and derivatives 17 with substituents at the benzene ring and/or the 2-position are conveniently prepared in high yield by fusing anthranilic acid derivatives 16 with amides or thioamides. The synthesis was first reported by von Niementowski in 1895 and is best suited for the preparation of 2-unsubstituted quinazolin-4(3i/)-ones by the fusion of anthranilic acid derivatives with formamide. Homologous acylamides require higher tempera-... 

Quinazolines can be prepared by several methods. AT-Acylanthranilic acids undergo cyclization with ammonia or primary amines via amides 14 forming quinazolin-4(3ii0-ones 15 (Niementowski synthesis). Alternatively o-(acylamino)benzaldehydes or -acetophenones react with ammonia producing quinazolines 16 (Bischler synthesis) ... 

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