Allyl Ethers and Homologs

The hydroformylation of allyl ethers with cumenyl, isobornyl, 2-methyl-2-pentanol, and terpinyl groups was patented by IFF (Table 6.4) [186]. In all cases, the linear and branched aldehydes were formed. After distillation, the odors of the linear compounds were evaluated. The isobornyl-derived aldehyde was reduced to give a corresponding hydroxy butylether with a typical patchouli aroma. 

In the same manner, also related branched allyl ethers were subjected to similar reaction conditions (Table 6.5) [186,187]. 

By application of these substrates, some of which were characterized by a distinctive odor, exclusively the terminal 4-oxysubstituted 3-methylbutyraldehydes yielded. The cumyl-derived aldehyde was converted into the primary alcohol by using NaBH,j [186]. The alcohol showed a nutty woody ozoney, fresh air cloth, and green-orange aroma profile. 

The hydroformylation, which, for example, was carried out in a 430 g scale, gave rise to the corresponding 5-formyl-l,3-dioxepane with an odor reminiscent of fresh sea breeze and lily of the valley. As a side product, 4-formyl-l,3-dioxepane was formed in 10% yield. It could be easily removed by distillation. Based on this protocol, numerous other ketones and aldehydes, respectively, were reacted with 

4-butene-diol derivatives and subsequently hydroformylated with unmodified or PPhg-modified Rh catalyst to give products with quite different but useful fragrance properties. Interestingly, the related 4- or 7-formyl-substituted analogs are not useful as aroma compounds [189]. 

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