ChemInform Abstract: A Novel Bis‐Thiourea Organocatalyst for the Asymmetric Aza‐Henry Reaction.

Abstract

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Enantioselective Organocatalytic Direct Michael Addition of Nitroalkanes to Nitroalkenes Promoted by a Unique Bifunctional DMAP-Thiourea

“…7 Recently, we have found that as little as 2 mol% of a simple nonchiral thiourea can accelerate this reaction while suppressing oligomer formation. 8 Herein, we report on the development of a highly enantioselective version of this reaction using a novel bifunctional thiourea catalyst that was rationally designed for this particular transformation.…”

“…All of the reactions in Table 1 produced only small amounts of polymer or oligiomers which can be the exclusive product when substoichiometric amounts of a base is used as catalyst. 8,16 Since catalyst 8 is sluggish for this reaction under neat conditions, 5c it was not surprising to find that it is even more sluggish when a solvent is used (entry 1). To optimize turnover, the reaction of 1-nitropropane and nitrostyrene was investigated with decreasing amounts of the catalyst (R)-9, and as expected, the rate of the reaction decreased with decreasing amounts of the catalyst.…”