Orthoamide und Iminiumsalze, XCIV^a. Kondensationsreaktion von Orthoamiden von Alkincarbonsäuren mit 2-Methyl-5-phenacyl-1,3,4-thiadiazolen

Abstract

The ketene aminals 9a–e can be prepared from the orthoamide of propiolic acid 6a and 2-methyl-5-phenacyl-1,3,4-thiadiazoles 8a–e under mild conditions. The crystal structure analyses of 9b and 9d reveal that compounds 9 can be regarded as 1,4-dipoles (push-pull-substituted butadienes). Surprisingly, the analogous reactions of the orthoamides 6b,c with the thiadiazoles 8a–c give rise to the formation of 1,2-dihydro-pyridin-2-thiones 13a–j. The constitution of the compounds 13 was confirmed by crystal structure analyses of the compounds 13c,f,g,i.