thiourea and carbene

Stereochemical control during polymerization is a key strategy of polymer chemistry to achieve semicrystalline engineered plastics. The stereoselective ring-opening polymerization (ROP) of racemic lactide (

Topics: Dioxanes; Methane; Plastics; Polyesters; Polymerization; Stereoisomerism; Thiourea; Toluene; Urea

Aliphatic amines strongly coordinate, and therefore easily inhibit, the activity of transition-metal catalysts, posing a marked challenge to nitrogen-hydrogen (N-H) insertion reactions. Here, we report highly enantioselective carbene insertion into N-H bonds of aliphatic amines using two catalysts in tandem: an achiral copper complex and chiral amino-thiourea. Coordination by a homoscorpionate ligand protects the copper center that activates the carbene precursor. The chiral amino-thiourea catalyst then promotes enantioselective proton transfer to generate the stereocenter of the insertion product. This reaction couples a wide variety of diazo esters and amines to produce chiral α-alkyl α-amino acid derivatives.

Topics: Amines; Amino Acids; Catalysis; Chemistry Techniques, Synthetic; Copper; Hydrogen Bonding; Kinetics; Methane; Molecular Structure; Stereoisomerism; Thiourea

Many hands make light work: In an organocatalytic asymmetric sulfonation of enones, the activation of a sulfonyl imine by an N-heterocyclic carbene (NHC) catalyst led to the release of a sulfinic anion, which underwent nucleophilic addition to the enone. The enantioselectivity of the process was controlled by a chiral thiourea/amine co-catalyst through anion recognition and hydrogen-bonding interactions. Tol=p-tolyl.

Topics: Amines; Catalysis; Heterocyclic Compounds; Imines; Ketones; Methane; Stereoisomerism; Sulfones; Thiourea