4- Amino-1 //-imidazo quinazoline

Ishikawa, R, Saegusa, J., Inamura, K., Sakuma, K., Ashida, S.-I. Cyclic guanidines. 17. Novel (N-substituted amino)imidazo[2,l-h] quinazolin-2-ones water-soluble platelet aggregation inhibitors. J. Med. Chem. 1985, 28, 1387-1393. 

Cyclization of either 3-allyl-4-imino-2-mercaptoquinazoline (154) [77IJC(B)751 ] by heating with polyphosphoric acid or N-(4-quinazolinyl)-a amino acids (156) (76KGS1268) by heating with a mixture of acetic anhydride and acetic acid was reported to afford the imidazo[l,2-c]-quinazolines 155 and 157, respectively. 

Aryl-5,6-dihydrobenzo[4,5]imidazo[l,2-C]-quinazolines Isatoic anhydride could also be reacted with amino-, hydroxyl- or thiolanilines to form 2-(2-aminophenyl)benz-imidazoles, oxazoles or thiazoles, Scheme 5.38. In the case of 2-(2-aminophenyl)benzimidazoles (X=N), the product was formed after 3 min at 150°C in acetic acid. The products could subsequently be further elaborated 6-aryl-5,6-dihydrobenzo[4,5]imidazo[l,2-C]quinazolines, a four ring system, was formed by treatment of the 2-(2-aminophenyl) benzimidazole (X=N) with different aldehydes in acetic acid at 150°C for 5 min (J. Westman, and K. Orrling, Personal Chemistry, Uppsala, Sweden, unpublished results). Fifteen compounds were synthesised in 20-75% overall yield. This 3 + 5 min procedure should be compared to the conventional heating protocol developed by Devi and co-workers57, where each reaction step was run overnight to eventually afford the products in only 30-50% yield. 

Imidazo[4,5-0]quinazoline-4,9-diones (406) were synthesized as purine mimics. They were obtained from the 4-amino precursor and Fremy s salt or from the 4,9-unsubstituted derivatives with nitrogen dioxide. In strong acid, a diprotonated quinone is present (86JOC4784). 

Imidazo[4,5-c]quinolin-2-ones. In a continuation of the work that led to the isolation and characterization of the series of 2,6-dihydroimidazo[l,5-c]quinazoline-3,5-diones described in this section, Klasek and co-workersinvestigated the reaction of analogues of 145 bearing 3-amino substituents as shown in Scheme 6. To characterize these products, the authors again resorted to long-range correlation data. For 148,... 

Many ring-fused imidazole derivatives have been synthesized by various methods. Domino Michael addition retro-ene reaction of 2-alkoxyiminoimidazolidines and acetylene carboxylates provided a synthesis of 2,3-dihydroimidazo[l,2-a]pyrimidin-5-(l//)-ones <05T5303>. A single step synthesis of 3,5-dialkyl-9-nitroimidazo[l,2-c]quinazolin-2(3//)-ones from simple carbonyl compounds, primary amines or amino acid methyl esters and 2-azido-5-nitrobenzonitrile has been published <05TL5778>. Diels-Alder reaction of azadienes and benzimidazole-4,7-diones afforded imidazo[4,5-g ]quinoline-4,9-dione derivatives <05EJ01903>. Reaction between isocyanides and dialkyl acetylenedicarboxylates in the presence of 4,5-diphenyl-l,3-dihydro-2//-imidazol-2-one provided a one-pot synthesis of 5//-imidazo[2,l-ft][l,3]oxazine derivatives <05T2645>. Microwave irradiation was employed in the synthesis of 1-ary 1-3-acetyl-1,4,5,6-... 

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