Thioacids and thioacid salts for determining the enantiomeric excess of chiral compounds containing an electrophilic carbon center

A composition comprising a compound of formula I or a salt thereof,

• wherein R1, R2, and R3 are each independently (C1-C6)alkyl, (C3-C6)cycloalkyl, (C1-C6)alkoxy, aryl, aryloxy, aryl(C1-C3)alkyl, aryl(C1-C3)alkoxy, wherein any cycloalkyl, alkyl, or aryl group is optionally substituted with one or more halo, oxo, hydroxy, methoxy, ethoxy, acetoxy, acetamido, cyano, nitro, nitroso, methylmercapto, ethylmercapto, carboxyl, sulfonate, or sulfinate groups;
• and wherein any cycloalkyl or aryl group is additionally optionally substituted with one or more methyl or ethyl;
• wherein none of R1, R2, and R3 are identical to each other, and no two of R1, R2, and R3 are linked together to form a cycloalkyl or aryl ring.