Hydroformylation for the Production of Flavors and Fragrances

Short-chain C3-C5 aldehydes accessible by hydroformylation, such as isobu-tyraldehyde, isovaleraldehyde, and 2-methyl-butyraldehyde, are used only rarely in fragrance compositions. They are characterized by a fruity and roast odor [42]. More important are linear and branched aldehydes with longer carbon chains. Typical examples are -hexanal, n-octanal, n-decanal, -undecanal, -dodecanal, and -tridecanal. Their odor detection threshold in water is between 4.5 ppb 

Currently, the workhorse in hydroformylation that converts a range of terminal long-chain olefins with high activity and w-regioselectivity into the corresponding n-aldehydes is a Rh catalyst modified with the commercially available and cheap diphosphite ligand BIPHEPHOS [48] (used for inexpensive floral notes) [49]. 

Entry Olefin Aldehyde Conversion (%) Aldehyde (%) //6 ratio TOFth ) 

Since the hydroformylation of 1-octene under the formation of -nonanal (pelargonaldehyde) is a model reaction in academia for testing new reaction conditions in hydroformylation, several efficient methods have been developed. The reaction works well with a Rh(BIPHEPHOS) catalyst (compare Table 6.1, entry 3). Alternatively, internal octenes can be used under the conditions of isomerizing hydroformylation [53]. The aldehyde is naturally occurring in citrus and rose oils. It has a fatty-rose-like odor and confers floral perfumes a typical rose nuance. 

The current market of MNA is estimated to be 500-600t/a. Important producers or/and suppliers are Symrise, Givaudan, Firmenich, and Kao Corporation. MNA possesses an odor that differs strongly from that of other aldehydes. Its animal note is highly appreciated in perfume accords, for example, for the manufacture of the famous feminine perfume Chanel N 5. 

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