Catalyst Controlled Site- and Stereoselective Rhodium(II) Carbene C(sp 3 )-H Functionalization of Allyl Boronates.

Rhodium(II) catalyst-controlled site- and stereoselective carbene insertion into the distal allylic C(sp 3 )-H bond of allyl boronates is reported. The optimum chiral catalyst for this reaction is Rh 2 ( S -TPPTTL) 4 . The fidelity and asymmetric induction of this catalytic transformation allows for a highly diastereoselective and enantioselective C-C bond formation without interference from the allyl boronate functionality. The resulting functionalized allyl boronates are susceptible to stereoselective allylations, generating products with control of stereochemistry at four contiguous stereogenic centers.