1958 年 78 巻 6 号 p. 594-597
When acetyl, benzoyl, and phenylacetyl derivatives of ethyl dl-4-(2-piperidyl) butyrate are dry distilled with the same or twice the amount of soda lime, 4-methyl-, 4-phenyl-, and 4-benzyl-Δ3-dehydroquinolizidines are obtained in respective yield of 97%, 93%, and 95%, with generation of slight ammonia odor. These bases are unstable and colored in the air but their picrates and perchlorates form stable dehydroquinolizidinium salts and do not undergo any change even when heated in air at 120-130°.
Catalytic reduction of these bases in ethanol with palladium-carbon catalyst easily afforded 4-alkyl- or 4-arylquinolizidines in quantitative yield. It was found from these facts that this kind of cyclization reactions reported to date do not necessarily require the formation of enol type by the carbonyl group of the acid amide.