Tandem hydroformylation-acetalization of para-menthenic terpenes under non-acidic conditions

α-Terpinene, γ-terpinene, terpinolene, and limonene can be selectively transformed in corresponding diethylacetals in ethanol solutions containing [Rh(COD)(OMe)] 2 and triphenylphosphine or tris( O- tbu-phenyl)phosphite under mild non-acidic conditions through the hydroformylation and consecutive on...

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Bibliographic Details
Published in:	Applied catalysis. A, General Vol. 380; no. 1; pp. 125 - 132
Main Authors:	Vieira, Camila G., da Silva, José G., Penna, Cristiano A.A., dos Santos, Eduardo N., Gusevskaya, Elena V.
Format:	Journal Article
Language:	English
Published:	Kidlington Elsevier B.V 31-05-2010 Elsevier
Subjects:	Accounting Acetalization Catalysis Chemistry Dienes Ethanol Ethyl alcohol Exact sciences and technology General and physical chemistry Hydroformylation Ligands Monoterpenes Rhodium Terpenes Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry Toluene Acetalization Monoterpenes Rhodium Hydroformylation 1,8-p-Menthadiene Rhodium complex Catalytic reaction Hydrocarbon Ethanol Toluene Alcohol Transition metal Aldehyde Dienic compound Substrate Acetal Terpene Acids Alkanol Benzenic compound Monoterpene Chemical reactivity Platinoid Catalyst
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Summary:	α-Terpinene, γ-terpinene, terpinolene, and limonene can be selectively transformed in corresponding diethylacetals in ethanol solutions containing [Rh(COD)(OMe)] 2 and triphenylphosphine or tris( O- tbu-phenyl)phosphite under mild non-acidic conditions through the hydroformylation and consecutive one-pot acetalization of primarily formed aldehydes. One to three main fragrance para-menthenic acetals account for 70-90% of the mass balance for each substrate. Rhodium-catalyzed tandem hydroformylation/acetalization of a series of para-menthenic terpenes, i.e., α-terpinene (1), γ-terpinene (2), terpinolene (3), and limonene (4), has been studied in ethanol solutions in the presence of PPh 3 or P(O- o- tBuPh) 3 as auxiliary ligands. Limonene gives a corresponding acetal in high yields in both systems. The reaction with conjugated diene 1 occurs in the presence of PPh 3 at a reasonable rate giving aldehydes and acetals only as minor products. On the other hand, non-conjugated dienes 2 and 3 has showed an extremely low reactivity in the Rh/PPh 3 system. The use of P(O- o- tBuPh) 3 not only remarkably accelerates the hydroformylation of all four substrates but also increases significantly the acetalization activity of the catalytic system. With the Rh/P(O- o- tBuPh) 3 system, the mixtures of fragrance acetals have been obtained from substrates 1–3 in excellent combined yields, with two or three main acetals accounting for 70-85% of the mass balance for each substrate. The process is performed under mild conditions and in the absence of acid co-catalysts. The hydroformylation of all substrates in ethanol solutions was found to be much faster than in toluene.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0926-860X 1873-3875
DOI:	10.1016/j.apcata.2010.03.045