Hydroformylation of linalool

Benaissa M, Jauregui-Haza UJ, Nikov I, Wilhelm AM, Delmas H (2003) Hydroformylation of linalool in a supported aqueous phase catalyst by immobilized rhodium complex kinetic study. Catal Today 79-80 419-125. doi 10.1016/s0920-5861(03)00074-9... 

Catalyst 18 was then used to investigate the kinetics of the hydroformylation of linalool in toluene (Scheme 10) [36]. The reaction proceeded well with the aldehydes being the sole products. The selectivity in favour of the linear aldehyde was in the region of 70%. 

A typical example is the hydroformylation of linalool, a monoterpenoid allyhc alcohol with a pleasant lily odor. It is a key building block for the synthesis of various vitamins and fragrances, such as vitamin A, vitamin E, citral, citronel-lol, and phnol (see Scheme 6.44). Linalool is found in the essential oils of several plants, for example, Brazihan rosewood and Chinese Ho leaf oils, but mostly it is produced industrially from a-pinene or from the petrochemically derived source 6-methylhept-5-en-2-one (Hoflimann-La Roche Process) [144]. 

Rhodium-catalyzed hydroformylation of linalool gave almost quantitatively a cyclic hemiacetal in toluene solutions (Route I) and a corresponding mixed acetal in ethanol solutions (Route II, Scheme 6.48) [93, 145]. The reaction occurred 2 times faster in ethanol than in toluene solutions and 10 times faster with the Rh/P(O-0-iBuPh)3 system as compared to the catalytic system with PPhj as ligand. Recently, the reaction was run successfully in an aqueous two-phase system [94]. Both hemiacetal and acetal are compounds with fresh floral and/or citrus notes [22a]. 

The turnover frequencies measured at different temperatures were comparable to those found for hydroformylations using other strategies [1,3,33,35]. To develop the kinetic model, the effects of the linalool and the catalyst concentration and of the total carbon monoxide and hydrogen pressure on the outcome of the hydroformylation were investigated. In all cases, the reaction rate was enhanced by a first-order dependence. The results were in good agreement with the calculated model. The activation energy was found to be 14.5 kcal mol h... 

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