Wolff rearrangement silver -promoted

The main synthetic application of the Wolff rearrangement is for the one-carbon homologation of carboxylic acids.242 In this procedure, a diazomethyl ketone is synthesized from an acyl chloride. The rearrangement is then carried out in a nucleophilic solvent that traps the ketene to form a carboxylic acid (in water) or an ester (in alcohols). Silver oxide is often used as a catalyst, since it seems to promote the rearrangement over carbene formation.243... 

The Wolff and Amdt-Eistert rearrangements are probably among the earliest known reactions promoted by silver ions.2,3 Discovered at the turn of the nineteenth/ twentieth century, the Wolff rearrangement allows the transformation of a-diazo-ketones to carboxylic acids,4 while the Arndt-Eistert rearrangement is a similar sequence also leading to carboxylic acids, but including the preparation of a-dia-zoketones from a shorter acid chloride (Scheme 3.1).5... 

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