Rhodium(i)-catalyzed stereoselective [4+2] cycloaddition of oxetanols with alkynes through C(sp)-C(sp) bond cleavage.

An efficient and convenient synthesis of highly functionalized dihydropyrans has been achieved through rhodium(i)-catalysed tandem C(sp)-C(sp) bond cleavage and annulation of oxetanols with alkynes. An enantioselective version was enabled using a Binaphine ligand. Excellent site-selectivity and remarkable enantioretention are obtained for 2-substituted oxetanols.