Novel Dehydrations and Dehydrogenations of Terpin Hydrates (1, 8- and 1, 4- Terpin)

Abstract

Novel dehydrations and dehydrogenations of 1, 8-terpin hydrate (1) and 1, 4-terpin hydrate (2) were carried out using copper and zinc (Cu-Zn) system, synthetic zeolites (A-3, A-4, A-5 and F-9) or polar aprotic solvents [dimethyl sulfoxide (DMSO), N, N-dimethyl formamide (DMF), ethylene carbonate (EC) and sulfolane (SF)] as catalysts. With the Cu-Zn system catalyst, the dehydration or dehydrogenation of (1) and (2) gave α-terpinene (5) and 1-methyl-4-isopropenyl benzene (7), respectively, as major products. With DMSO or A-3 zeolite, the dehydration of (1) gave predominantly β-terpineol (10) in high yield (87%). With DMSO, EC or A-4 zeolite, terpinene-1-ol (11) was obtained from (2) as the main product, amounting to 84% of the dehydration product under the best conditions. With SF or F-9 zeolite, terpinene-4-ol (12) was obtained as the main product from (2) in high conversion (80_??_82%) among dehydration products.