Journal
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
Volume 175, Issue 1-2, Pages 33-42Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/S1381-1169(01)00217-5
Keywords
monoterpenes; hydration; acetoxylation; heteropoly acid
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The liquid-phase hydration and acetoxylation of limonene (1), P-pinene (2) and alpha -pinene (3) catalyzed by dissolved or silica-supported heteropoly acid H3PW12O40 (PW) in acetic acid and acetic acid/water solutions have been studied. All three substrates give alpha -terpineol (4) as the main product along with alpha -terpenyl acetate (5). The reaction rate increases in the order: limonene < alpha -pinene < beta -pinene. Synthetically useful homogeneous and heterogeneous acetoxylation and hydration of 1, 2 and 3 into 4 and 5 have been developed. At room temperature under optimized conditions, 2 and 3 form a mixture of 4 and 5 with 85% selectivity at 90% substrate conversion. 1 gives 4 and 5 with 85% selectivity at 50% conversion, with the main product being ester 5 in acetic acid (4/5 similar to 30/70) and alcohol 4 in HOAc/H2O (90/10 v/v) solutions (4/5 similar to 85/15). Virtually no oligomerization of monoterpenes occurs under the optimized conditions. The catalyst can be separated without neutralization and may be reused. The PW shows a much higher catalytic activity than conventional acid catalysts such as H2SO4 and Amberlyst- 15. (C) 2001 Elsevier Science B.V. All rights reserved.
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