Abstract Dimethyl sulfoxide (DMSO) and tBu 2 C= C= O in diglyme require heating to about 150 C to furnish the Pummerer-type product tBu 2 CHCO 2 CH 2 SCH 3 through a novel mechanistic variant. The “ester enolate” tBu 2 C= C (O–)–O–S+(CH 3) 2 arising through the reversible addition of DMSO (step 1) to C-1 of tBu 2 C= C= O must be trapped through protonation (step 2) at C-2 by a carboxylic acid catalyst to form tBu 2 CH–C (= O)–O–S+( ...
