Highly Selective Synthesis of Octahydroaminoacridine over Mesoporous ZnAlMCM-41 Catalysts

Abstract

A very ecofriendly heterogeneous catalytic method has been used for the highly selective synthesis of octahydroaminoacridine/1,2,3,4,5,6,7,8-octahydroacridin-9-amine (OA) by a single-step vapor phase cyclization of cyclohexanone (CHCO) with a mixture of formamide (HCONH2) and ammonia (NH3) over different nanoporous catalysts, for example, mesoporous solid acid catalysts, ZnAlMCM-41, AlMCM-41, and ZnMCM-41, and microporous catalysts, for example, USY, Hβ, HZSM-5, and H-mordenite. In pharmaceutical companies, the main product, OA, is used as a drug intermediate in the production of tacrine that is a licensed drug, which is used for the treatment of Alzheimer’s disease. In order to determine their catalytic stabilities, recyclable mesoporous ZnAlMCM-41 catalysts have been reused in this reaction. To find an optimal parameter for highly selective synthesis of OA, various reaction parameters have been extensively investigated for this reaction. Additionally, an important byproduct, 1,2,3,4,5,6,7,8-octahydroacridine, is also formed by deamination of OA. The mesoporous ZnAlMCM-41(75) produces 92% OA selectivity with 100% CHCO conversion at 0.5 h–1 weight hourly space velocity and 340 °C with a feed ratio of CHCO/HCONH2/NH3 = 2:1:5. Interestingly, we have observed from the catalytic results of all the catalysts used for the single-step selective synthesis of OA that the ZnAlMCM-41(75) catalyst has higher OA selectivity with exceptional catalytic activity than other microporous and mesoporous catalysts.