Tandem Pummerer-type rearrangement and nickel-catalyzed alkylative olefination of the cyclic dithioacetal S-oxides of aromatic aldehydes with Grignard reagents

The cyclic dithioacetal oxides of aryl aldehydes undergo nickel-catalyzed croos-coupling with Grignard reagents to form olefins via two different routes. In the presence of an acidic proton at C-2, a Pummerer-type rearrangement initially occurs, followed by concurrent alkylation and double bond formation. Where the C-2 carbon is already functionalized with an alkyl or aryl group, Pummerer-type rearrangement is either unneeded or impossible and the oxide undergoes direct alkylative olefination to yield the same type of products.