Chiral Proline Amide‐Isothiouronium Salt Spaced with Diamine as an Efficient Bifunctional Organocatalyst for Enantioselective α‐Hydrazination of Aldehydes

The chiral proline amide‐isothiouronium salt‐based bifunctional organocatalyst was prepared by methylating of the corresponding chiral thiourea, containing more acidic and active N−H bonds compared to thiourea. This catalyst was applied to α‐hydrazination of aldehydes using azodicarboxylates, which can be transformed into β‐hydrazino alcohols, β‐amino alcohols, and α‐amino acid derivatives. Enantioselective α‐hydrazination of aldehydes has been successfully carried out with amide‐isothiouronium salt as a chiral catalyst. Various hydrazino aldehydes were obtained in high to quantitative yields and excellent enantioselectivities (of up to 99 % ee) in the presence of a benzoic acid additive. A chiral proline amide‐isothiouronium salt based bifunctional organocatalyst was prepared by methylation of the corresponding thiourea. This asymmetric catalyst facilitates α‐hydrazination of aldehyde with azodicarboxylates in high to quantitative yields and excellent enantioselectivities (of up to 99 % ee) in the presence of a benzoic acid additive.