Synthesis of α,β-unsaturated aldehydes and nitriles via cross-metathesis reactions using Grubbs’ catalysts

• Ru-catalysed cross-metathesis of electron-deficient olefins successfully carried out.
• Aldehydes/nitriles relevant to the fragrance industry prepared with good selectivity.
• Valuable intermediates derived from 2-allyloxy-6-methylheptane have been prepared.

A series of α,β-unsaturated aldehydes and nitriles of significant interest in the fragrance industry have been prepared using Grubbs’ catalysts in cross-metathesis reactions of electron-deficient olefins (i.e., acrolein, crotonaldehyde, methacrolein, and acrylonitrile) with various 1-alkenes, including 1-decene, 1-octene, 1-hexene and 2-allyloxy-6-methylheptane. The latter is of particular interest, as it has not previously being used as a substrate in cross-metathesis reactions and allows access to valuable intermediates for the synthesis of new fragrances. Most reactions gave good selectivity of the desired CM product (≥90%). Detailed optimisation and mechanistic studies have been performed on the cross-metathesis of acrolein with 1-decene. Recycling of the catalyst has been attempted using ionic liquids.

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