384. Researches in the methone series. Part XVIII. Pyrolysis of (–)-menthyl acetate

Abstract

2067 384. Researches in the Menthone Series. Part X VIII.* Pyrolysis of (-)-Menthy1 Acetate.

The Stereoisomerism of Cyclohexane Derivatives.

“…The experimental data, as presented in the text of his paper, show the product from (+)-neomenthyltrimethylammonium hydroxide to be 80 per cent 2-p-menthene and 20 per cent 3-p-menthene instead of the inverse ratio listed in the table. Moreover, the recent data of McNiven and Read (193) show that this reaction yields 10.5 per cent (+)-¿rans-2-p-menthene and 89.5 per cent 3-p-menthene. From these results it follows that the Hofmann rule does not control eliminations in such ring systems.…”

“…Further evidence for the configuration of menthol has been provided by pyrolysis of (-)-menthyl acetate and of (-)-menthyl chloride (193). As in the case of the xanthate, the structure of (-)-menthyl acetate will permit cis elimination between Cs and C3 or C3 and C4, whereas trans elimination would involve Cs and C3.…”

“…The homogeneous unimolecular thermal decomposition of (-)menthyl chloride yields a mixture of 2-p-menthene and 3-p-menthene in the ratio of 1:3, thus confirming the structure shown in formula XXIII. 3 Another approach to the configurational characterization of the menthols has involved thermal decomposition of the optically active quaternary ammonium hydroxides to yield optically active menthenes (193): interpreted on the basis of the following configurations of the starting materials (cf. figure 5):…”