Organocatalytic Enantioselective Synthesis of 2,3-Allenoates by Intermolecular Addition of Nitroalkanes to Activated Enynes

The first efficient intermolecular addition of nitroalkanes to activated enynes for asymmetric synthesis of 2,3-allenoates is described. It is a new addition to the limited available strategies for catalytic asymmetric synthesis of allenoates. Enabled by a new bifunctional catalyst, a range of trisubstituted allenoates can be obtained in excellent chemical and optical purity. These allenoate products with a pendant 2-nitroethyl alpha-substituent are useful chiral building blocks.