Imidazo quinolines, formation

Figure 1. Suggested route for the formation of the imidazo-quinoline compounds.

FIGURE 7.3 Suggested pathway for the formation of imidazo-quinolines and hnidazo-quinoxalines. (Adapted from Jagerstad, M. et al. 1998. Z. Lebensm. Unters. Forsch. A 207 419-427. With permission.)... 

The hydrolysis proceeds via a diazafulvene intermediate, which in these systems can be formed without a total loss of aromatic character of the tricycle. It is tempting to suggest that, using this reasoning, linearly annelated 2-trifluoromethyl-imidazo[4,5-g]quinoline should be inert toward alkaline hydrolysis, as formation of the diazafulvene intermediate will again involve total dearomatization of the heterocyclic system (Scheme 36). 

Condensation of endione 328 with aminal 329 in acetonitrile gave the imidazo[l,2-fl]quinoline 330 via the formation of a C-C bond intermediate. Alternatively, 330 was prepared in a one-pot reaction by refluxing 1 with 329 and benzaldehyde in acetonitrile (99JCS(P1)2087). When the enamine 31 (R = CH2CC>2Et), obtained from reaction of 1 and ethyl glycinate, was reacted with 2-(3-nitrobenzylidene)malononitrile, it gave 330 (R = CN, Y, X = O) via the formation of 2-aminoquinoline 331 that spontaneously cyclized to 330 (01ARK73) (Scheme 62). 

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