A unique synthesis of N-(Z)-5-bromo-6-hydroxyhexahydro isobenzofuran-1(3H)-ylidene)methanaminium bromide

Substituted cyclohexane derivatives are used as key compounds in the synthesis of different natural or synthetic compounds. In this context, we synthesized a new 1,6-disubstituted cyclohexene derivative and studied its bromination reaction. First, we obtained carboxamide 11 containing three functional groups by reduction of tetrahydro-1H-isoindole-1,3(2H)-dione with NaBH4. Bromination of carboxamide 11 gave the interesting rearrangement product hexa-hydroisobenzofuran-1(3H)iliden)methanaminium depending on the groups in the cyclohexene ring and its exact configuration was determined by X-ray analysis. Hydrolysis of the iminium salt gave 5-bromo-6-hydroxyhexyhexahydro isobenzofuran-1(3H)one. The reaction mechanism for the rearrangement product was proposed. As a result, two unexpected reactions occurred in the bromination reaction. The first is the incorporation of halohydrin into the molecule in anhydrous medium and the second is the facile formation of the five-membered lactone ring. [Graphical Abstract]