Base-tuned selective 1,2-dichloromethylhydroxylation and 1,2-peroxyhydroxylation of 1,3-dienes via a tandem radical process.

A catalyst-free 1,2-difunctionalization of 1,3-dienes with CHCl 3 and TBHP in the presence of NEt 3 to give the dichloromethylhydroxylation products was developed. Various substituents on the aryl ring of the dienes tolerated the reactions and gave the corresponding products in moderate to good yields. When Na 2 CO 3 was employed as the base, the key intermediate α-amino radical could not be formed; therefore, 1,2-peroxyhydroxylation products were obtained instead. This protocol provides an effective and functional group tolerant strategy for diene 1,2-difunctionalization, thus providing great potential for further functionalization and modification of synthetic molecules.