Research of the Ozonolitic Conversion of R-(-)-Carvone in Methanol in the Presence of Pyridine

Abstract

Carvone is a menthane monoterpenoid, a component of essential oils of cumin and dill, Mentha spicata, known for its antimicrobial, nematicidal, antitumor, and plant growth regulating properties. S-and R-carvones are used in the synthesis of compounds with practically important properties: sesqui-and diterpenes, alkaloids, macrolides, insect pheromones, and steroid systems. This terpenoid is also of great interest as a substrate for ozonolytic transformations due to the simultaneous presence of disubstituted and conjugated double bonds in the structure. There are many reagents for the transformation peroxide products of ozonolysis, both reducing and oxidizing reagents are traditionally used. Recently, however, the socalled "non-peroxide" ozonolysis in the presence of peroxide oxygen acceptor compounds (tertiary amines, pyridine), which allows one-stage obtaining of O-containing compounds without the use of additional reducing agents, has attracted interest. Previously, we have carried out ozonolytic transformations of (R)-(-)-carvone in the presence of pyridine without the use of additional reducing agents. It was found that the exhaustive ozonolysis of R-(-)-carvone in a MeOH-Py mixture after treatment with a 5% HCl solution leads to a mixture of monomethyl ester of 3-acetylpentadiic acid and 2,8-dioxo-1-methylbicyclo[3.3.0]octane-3,7-dione. In this study, as a result of processing the reaction mixture in two versions (5% HCl solution or saturated CuSO4 solution), it is shown that 2,8-dioxo-1-methylbicyclo[3.3.0]octane-3,7-dione is a product of cyclization of 3-acetylpentadiic acid monomethyl ester under acidic conditions. When determining the role of pyridine in the ozonolytic transformations of (R)-(-)-carvone, it was found that the treatment of peroxide products of carvone ozonolysis with pyridine did not lead to their complete reduction. The preparation of carbonyl and carboxyl compounds from (R)-(-)-carvone is most preferable by ozonation in the presence of pyridine.