A new bifunctional thiourea featuring a methylated pyridinium ion and a chiral amine is reported. This readily prepared organocatalyst is more active than its analogous 3,5bis(trifluoromethyl)phenyl substituted thiourea ("Takemoto's catalyst"), significantly reducing reaction times in the Michael additions of diethyl malonate and other pronucleophiles to various aryl nitroolefins. Excellent enantioselectivities accompany this enhanced rate, particularly at colder reaction temperatures where the neutral catalyst is less efficient (i.e., 91-98% in most cases). Aggregation studies suggest that the self-recognition and dimerization of the charged catalyst is not dissimilar to what is typical of other amino-thioureas, indicating that electrostatic enhancement is viable as a general design strategy to improve additional bifunctional organocatalysts.

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