Diastereoselective titanium-mediated construction of cis-2,3-ring annelated 1-(2'-chloroethyl)cyclopropanols.

Titanium(IV)-mediated cyclopropanation induced by reaction of cycloalkylmagnesium bromides 1a-e in the presence of titanium tetraisopropoxide with ethyl beta-chloropropionate 2 yielded cis-fused 1-(2'-chloroethyl)cyclopropanols 3b-e with diastereoselectivity highly depending on the ring size. Unexpected rearrangement products 5d,e were isolated in some cases.