Abstract
Hydrolytic cyclization of 3-acetyl-3-(3, 4-dimethoxyphenyl) adiponitrile (V) in 65% sulfuric acid at 140° was found to yield 3a-(3, 4-dimethoxyphenyl)-2, 3, 3a, 4, 5, 6-hexahydroindol-2, 6-dione (VI), whose structure was confirmed by spectral properties and transformation into dl-mesembrane (=3a-(3, 4-dimethoxyphenyl)-1-methylperhydroindol) (XI). Reactions of V in 65% sulfuric acid at room temperature yielded five products, XIII, XIV, XV, XVI and XVII as intermediates of this cyclization reaction, all of which were converted to the final cyclization product (VI) by heating to 140°in the acid. Possible reaction mechanisms of the formation of VI and the intermediates were proposed. An alternate synthesis of VI from 3, 4-dimethoxyphenyl acetone via methyl 3-(2-cyanoethyl)-3-(3, 4-dimethoxyphenyl) levulinate (XIX) was also described.
