FREE-RADICAL REARRANGEMENT OF UNSATURATED SULFONES INVOLVING AN INTRAMOLECULAR HYDROGEN ABSTRACTION

5-(p-Tolunesulphonyl)-1-alkenes CH2=CHCH2CH2CH(SO2pTol)CHR1R2 (R1=Ph o r Me, R2=OH; or R1=R2=Me) underwent rearrangement to give pTolSO2CH2CH 2CH2CH2CH=CR1R2 (which tautomerise to ketones when R2=OH) upon treatme nt with benzoyl peroxide in tBuOH or pTolSO2Na inaqueous AcOH. The rel ative reactivities of the substrates can be rationalised in terms of t he proposed reaction mechanism, namely a free radical chain involving, as propagating steps, sulphonyl radical addition to the double bond o f the sulphone, 1,5-hydrogen shift, and beta-scission of the resulting beta-sulphonyl alkyl radical.