Squaramide-catalysed enantio- and diastereoselective sulfa-Michael addition of thioacetic acid to α,β-disubstituted nitroalkenes

A highly enantio- and diastereoselective sulfa-Michael addition of thioacetic acid to α,β-disubstituted nitroalkenes catalysed by a chiral squaramide organocatalyst has been described. This organocatalytic reaction at an extremely low catalyst loading (0.2 mol%) furnished synthetically useful β-nitro sulfides in excellent yields with good diastereoselectivities and high enantioselectivities (up to 94 : 6 dr, 95% ee). In addition, the catalytic reaction can be performed on a 10 gram scale, and facile transformation into taurine derivative is also presented.