Aniline derivatives reaction with dicarbonyl

More recently, a catalyst-free aqueous version of this strategy was proposed with simple acyclic 1,3-dicarbonyls, formaldehyde, and styrene or anilines derivatives (Scheme 40) [131], In the first case (Scheme 40), the very reactive 2-methylene-1,3-dicarbonyl intermediate reacts smoothly at 80°C with a variety of substituted styrenes to give the corresponding dihydropyrans in moderate to good yields. Remarkably, when styrenes were replaced by A-ethylaniline, a novel five-component reaction involving twofold excess of both formaldehyde and 1,3-dicarbonyl selectively occurred (Scheme 41). The result is the formation of complex fused pyranoquinolines following a Friedel-Craft alkylation - dehydration sequence to furnish the quinoline nucleus, which suffers the Hetero-Diels-Alder cyclization in synthetically useful yields. 

Solid-solid reactions 2.00 mmol of the 1,3-dicarbonyl compound 1 or 4 and 2.00 mmol of the solid aniline derivative 2 were ball-milled at room temperature for 30 min. After drying of the solid hydrates at 0.01 bar at 80 °C the pure enam-ine ketones 3 or 5 were obtained with quantitative yield. 

Aminomethylene derivatives of ketones and 1,3-dicarbonyls are used in order to incorporate a formyl group into CH-acidic heterocycles via initial reaction with ethyl orthoformate and aniline followed by hydrolytic cleavage, as is shown e.g. with barbituric acid301 (equation 224). 

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