Unusual α-hydroxyaldehyde with a cyclopentane framework from verbenol epoxide

Reactivity of verbenol and verbenone epoxides in supercritical solvents

“…In the presence of ZnBr 2 verbenol epoxide 5 transforms into compound 7, 12 while in the presence of Montmorillonite clay the main product is compound 6 (44% yield); compounds with cyclopentane skeleton 7 and 8 are formed in smaller quantities (16 and 10%, respectively). 3 Our results in this flow system are more similar to those on clays then to those catalyzed by ZnBr 2 .…”

“…Additionally, a very small amount of α-hydroxy aldehyde 8 was formed, as in earlier studies in the presence of Montmorillonite clay. 3 In considering how 8 could form, the authors 3 suggested a quite complex multi-step scheme which assume compound 8 to form from verbenol epoxide 5 via specific adsorption of the latter on the catalyst surface, though a comparable explanation cannot apply here. Heating verbenol epoxide 5 in this way gave a large amount of unidentified products, making up about half of the reaction products; the main by-product did not exceed 5% of this.…”

“…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 .…”

Prins cyclization: Synthesis of compounds with tetrahydropyran moiety over heterogeneous catalysts

“…(1R,2R,6S)-Diol can be synthesized from carvone [15], but the most effective way leading to this compound with high stereoselectivity starts from (-)-verbenone and includes three stages: epoxidation of verbenone to verbenone oxide with hydrogen peroxide in alkali/methanol solution, reduction of verbenone oxide using LiAlH 4 and subsequent isomerisation of obtained verbenol oxide [16,17]. Verbenone is a natural organic compound which can be found in a variety of plants or synthesized by allylic oxidation of α-pinene [18].…”

Environmentally Benign Transformations of Monoterpenes and Monoterpenoids in Supercritical Fluids

“…The main products of the reaction at 413 K were keto alcohol 29 (44%) and diol 28 (30%); a-hydroxy aldehyde 30 was also identified with 2% yield (Scheme 6) [32]. The product distribution was similar to that obtained in the presence of montmorillonite clay [34] and differed sufficiently from that in the presence of ZnBr 2 [35].…”