Asymmetric decarboxylative 1,4-addition of malonic acid half thioesters to vinyl sulfones: highly enantioselective synthesis of 3-monofluoromethyl-3-arylpropanoic esters.

An asymmetric decarboxylative 1,4-addition of malonic acid half thioesters (MAHTs) to 2-aryl-substituted vinyl sulfones has been developed, yielding adducts with excellent enantioselectivity (up to 97 % ee). In view of tuning pKa values, a quinine-based benzyl-substituted thiourea was designed and demonstrated as the most efficient catalyst. The enantioselective synthesis of 3-monofluorinated analogues of 3-methyl indanone and (+)-turmerone has been accomplished from decarboxylative 1,4-addition adducts with satisfactory results.