Homopropargylic Ether Rearrangement via Gold Catalysis

Key words

gold catalysis - oxidative rearrangement - oxonium ylides

Significance

Gold catalysis has emerged as a powerful platform to conduct complex organic transformations. Specifically, the implementation of gold carbenoids has shown great promise in synthetic planning. These useful intermediates offer a convenient alternative to generate metal carbenes which are traditionally obtained from diazo compounds. The authors utilize these intermediates to synthesize α,β-unsaturated carbonyl compounds from homopropargylic ethers.

Comment

The authors report a silver-assisted gold(I)-catalyzed carbonyl synthesis. In an effort to obtain cyclobutanes 3 via a [1,2]-shift mechanism (path d), the authors unexpectingly obtained the corresponding α,β-unsaturated carbonyl compounds 2. Control experiments show that neither IMesAuCl, nor AgNTf₂ or HNTf₂ alone could catalyze the reaction. The scope of the reported reaction is quite broad; however, yields are generally moderate to good. In some instances cyclobutanones are obtained as the major product.