Calcium catalyzed hydroalkoxylation

A calcium catalyzed intramolecular hydroalkoxylation reaction is presented, as a transition metal free, inexpensive, and very mild process for the highly atom economic formation of cyclic ethers from γ,δ-unsaturated alcohols. In contrast to most of the previously reported procedures, room temperature conditions are fully sufficient in most cases for a high yielding cycloisomerization in the presence of a combination of 5 mol-% Ca(NTf2)2 and 5 mol-% Bu4NPF6. Full regioselectivity is observed in all transformations.