Ipsenol acylation

Silicon has also been used to control the acylation of 1,3-dienes in a manner analogous to the situation with alkenes. Isoprenylation with 2-trimethylsilylmethylbuta-1,3-diene follows the course expected of acylation of the allylic silane. In these very rapid reactions, titanium tetrachloride seems to be one of the more efficient catalysts, as is aluminum chloride. The method was used in synthetic approaches to the terpenes ipsenol (14) and ipsdienol (15 Scheme 16). Of particular interest is the comparison of this iso-prenylating agent with isoprene itself. The examples of Friedel-Crafts acylations cited show the regio-control that can be achieved by suitable choice of substrate. 

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