(The) radical allylation reactions

Abstract

Since radical alkylation of carbonyl compounds is not presently available, radical allylation using 2-phenylthio (2) and 2-benzyloxy allyl sulfone (5) as carbonyl equivalents was studied. Tin-mediated allylation was investigated with alkyl iodides, whereas allyl sulfones were used as radical precursors under tin-free conditions. Under tin-mediated condition, the allylation reactions worked well, giving the corresponding allylated products in good yields. The reaction of primary alkyl iodides with 2-substituted allyl sulfones gave better yields than that of secondary alkyl iodides. Under tin-free radical condition, the radical reaction with 2-phenylthio- and 2-benzyloxy allyl sulfone were not satisfactory, yielding several side products resulting from mainly [1,3]-rearrangement and hydrolysis. However, allylations worked well with other allylation reagents, irrespective of the structures of allyl sulfones. Furthermore, acylation and vinylation of β-carbonyl allyl sulfone as an electrophilic radical precursor proceeded but not very efficiently.