Rhodium catalyzed hydroformylation of monoterpenes containing a sterically encumbered trisubstituted endocyclic double bond under mild conditions

• Published in: Applied catalysis. A, General General, 2007-07, Vol.326 (2), p.219-226
• Main Authors: da Silva, José G., Barros, Humberto J.V., Balanta, Angelica, Bolaños, Alberto, Novoa, Maria L., Reyes, Marisela, Contreras, Ricardo, Bayón, J. Carles, Gusevskaya, Elena V., dos Santos, Eduardo N.
• Format: Article
• Language: English
• Subjects: 2-Carene; 3-Carene; Bulky phosphite; Catalysis; Chemistry; Exact sciences and technology; General and physical chemistry; Hydroformylation; Rhodium catalyst; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; α-Pinene
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2007.04.014

The rhodium catalyzed hydroformylation 2-carene ( 1), 3-carene ( 2), and α-pinene ( 3), in the presence of PPh 3 or various diphosphines and phosphites has been studied. The use of a bulky P(O- o- tBuPh) 3 ligand both improves the selectivity, and increases significantly the hydroformylation rate under relatively mild reaction conditions (80–100 °C, 40–80 atm). ▪ The rhodium catalyzed hydroformylation of endocyclic monoterpenes, that is, 2-carene ( 1), 3-carene ( 2), and α-pinene ( 3), in the presence of PPh 3 or various diphosphines and phosphites has been studied. The unmodified Rh catalyst promotes an intense isomerization of both carenes whose hydroformylation occurs rather slowly, and results in a complex mixture of aldehydes and alcohols. The addition of PPh 3, diphosphines or P(OPh) 3 in a P/Rh ratio as high as 20, efficiently prevents the isomerization, but the activity for hydroformylation is drastically reduced. On the other hand, the use of a bulky P(O- o- tBuPh) 3 ligand both reduces the isomerization, and significantly increases the hydroformylation rate. All three sterically crowded olefins 1–3 have been efficiently hydroformylated under relatively mild reaction conditions (80–100 °C, 40–80 atm) to a main aldehyde (2-formylcarane, 4-formylcarane, and 3-formylpinene, respectively) with good chemo- and regioselectivity, and almost 100% stereoselectivity for the trans isomers.