Reactions of Allyl Alcohols of the Pinane Series and of Their Epoxides in the Presence of Montmorillonite Clay

Abstract

The reactivity of allyl alcohols of the pinane series and of their epoxides in the presence of montmorillonite clay in intra-and intermolecular reactions was studied. Mutual transformations of (+)-trans-pinocarveol ((+)-2) and (À)-myrtenol ((À)-3a) were major reactions of these compounds on askanite-bentonite clay (Schemes 1 and 2). However, the two reactions gave different isomerization products, indicating that the reactivity of the starting alcohol (+)-2 or (À)-3a was different from that of the same compound (+)-2 or (À)-3 formed in the course of the reactions. (À)-cis-and (+)-trans-Verbenol ((À)-16 and (+)-12, resp.), as well as (À)-cis-verbenol epoxide ((À)-20) reacted with both aliphatic and aromatic aldehydes on askanite-bentonite clay giving various heterocyclic compounds (Schemes 4, 5 and 7); the reaction path depended on the structure of both the terpenoid and the aldehyde.

Unusual α-hydroxyaldehyde with a cyclopentane framework from verbenol epoxide

“…[2][3][4] Recently, 5 we found that the storage of (-)-cis-verbenol epoxide 1 on natural montmorillonite askanite-bentonite clay unexpectedly formed trans-diol 2 with a p-menthane framework as the major product (47%). Hydroxyketone 3, which had been obtained before as the major product of this reaction in the presence of ZnBr 2 , 6 was isolated in minor quantities (5%) (Scheme 1).…”

“…The mechanism suggested led to the formation of cation 7 at the key stage of the process. [a] 20 580 -44 (c 12, CHCl 3 )}, obtained from (-)-verbenone by oxidation with aqueous H 2 O 2 and further reduction with LiAlH 4 according to published procedures, 5,9 was added with stirring to a suspension of K10 clay (30.0 g, Fluka), preliminarily calcinated for 3 h at 120°C, in CH 2 Cl 2 (200 ml). The reaction mixture was stirred for 1 h at room temperature.…”

Reactivity of verbenol and verbenone epoxides in supercritical solvents

“…The 1 Н NMR spectra of compounds 5 coincided with those given in the literature. 2 Isopropyl alcohol contains no less than 99.8 wt. % of the main substance and no more than 0.05 wt.% of water.…”

“…Conversion products of this monoterpenoid are of great interest mainly due to their high biological activity, for example, compound 6 (Scheme 2) which can be obtained from verbenol epoxide 5 using Montmorillonite clays 2,3 demonstrates high antiepileptic 4 and antiparkinsonian 5 activities. Application of a flow technique for transformations of labile terpenoids such as compound 5 helps to avoid the use of acid catalysts and the inevitable difficulties associated with the catalyst separation, and may also improve the rate and selectivity of the transformations 6 .…”

Unusual Reactions of (+)‐Car‐2‐ene and (+)‐Car‐3‐ene with Aldehydes on K10 Clay

“…At the same time, it was logical to expect that the ratio of the diastereoisomeric products 16a and 16b would be the same, as in the case of 1, but in fact it was not so (16a/16b 7 : 1 from 1 and 20 : 1 from 2). Previously, we have already observed a considerable difference in the reactivity of monoterpenoids in the presence of clay, which depended on whether they were used as substrates or formed in the course of the reaction [17].…”