H. Yasuda, H. Midorikawa
Aug 1, 1966
Citations
0
Influential Citations
12
Citations
Journal
Bulletin of the Chemical Society of Japan
Abstract
Substituted 2-hydroxybenzaldehydes react with two equivalents of ethyl cyanoacetate to give α-β-(substituted 3-coumarinyl)-β-cyano-β-ethoxycarbonylethylenes in the presence of piperidine. When equivalent aldehyde and the cyanoacetate are used, substituted 2-imino-3-ethoxycarbonyl-2H-chromenes result, without the isolation of arylidenecyanoacetates. In o-hydroxyaryls, salicylic and o-thymotinic aldehydes, which give benzopyrane derivatives, are exceptional cases. 5-Phenylazo- and 5-nitro-2-hydroxybenzaldehydes result in the formation of coumarin derivatives. An abnormal condensation is also shown in the cases of 3, 5-dibromo-2, 4-dihydroxy-, 2-hydroxy-3-methoxy- and 2-hydroxy-4-methoxybenzaldehydes; i. e., the first one yields a 1:1-condensation product, while the last two give 3-cyanocoumarin derivatives, even with an excess of ethyl cyanoacetate. The condensation of m- and p-hydroxybenzaldehydes with ethyl cyanoacetate give the normally-expected arylidenecyanoacetates, even in the presence of a large exc...