A mild two-step process for the regioselective, transition-metal-free preparation of carbon-carbon bonds from allylic alcohols/ethers and Grignard reagents is described. This process obviates the need for the harsh deprotection conditions usually required for removal of methyl ethers. The synthesis is accomplished by photochemically promoted allylic substitution reactions of allylic alcohols and ethers with diethylphosphorothioic acid followed by sp(3)-sp(3) or sp(2)-sp(3) bond formation with various Grignard reagents under transition-metal-free conditions. Depending on the nature of the nucleophile, the regioselectivity of the carbon-carbon bond-forming event can be controlled to furnish either quaternary or tertiary carbon centers.