Heteroarylboronates in Rhodium-Catalyzed 1,4-Addition to Enones

Rhodium­(I)-catalyzed 1,4-addition of aryl and alkenylboronic acids to α,β-unsaturated carbonyl compounds is well established, but the transfer of heteroaryl residues in this reaction remains underdeveloped. We have studied heteroaryl MIDA and pinacol boronates as alternatives to the labile boronic acid counterparts. Under racemic conditions, 12 adducts with heteroaryl residues, among them unsubstituted 3- and 4-pyridinyl, 2-furanyl, thienyl, and pyrrolyl groups, were obtained in moderate to excellent yields. The enantioselective version of the reaction proved highly sensitive to the electronic character of the heteroaryl substituents, with boronates carrying electron-rich residues giving modest to high yields but consistently high enantiomeric excesses

Lewis Acid Catalyzed (3 + 2)-Annulations of Donor–Acceptor Cyclopropanes and Ynamides

The Sc­(OTf)₃-catalyzed (3 + 2)-annulation of donor–acceptor cyclopropanes and ynamides is described, providing the corresponding cyclopentene sulfonamides in good to excellent yield. Deprotection and hydrolysis of the resulting ensulfonamides delivers 2,3-substituted cyclopentanones with high diastereoselectivity