Catalytic Asymmetric Formal [3+2] Cycloaddition of 2-Isocyanatomalonate Esters and Unsaturated Imines: Synthesis of Highly Substituted Chiral γ-Lactams

Unlike their isocyano and isothiocyanato analogues, isocyanato esters remain almost unexplored as formal 1,3-dipoles in asymmetric catalytic reactions. The first asymmetric formal [3+2] cycloaddition involving isocyanato esters and electrophilic alkenes is reported. Diisopropyl 2-isocyanatomalonate reacts with α,β-unsaturated N-(o-anisidyl) imines in the presence of a Mg(OTf)₂ -BOX complex to give highly substituted chiral pyrrolidinones featuring a conjugate exocyclic double bond with excellent yields and enantiomeric excesses up to 99 %. Several transformations of the resulting heterocycles, including the synthesis of a pyroglutamic acid derivative, have been carried out.

Synthesis of (±)-Aphanorphine Using Rh-Catalyzed Cyclohydrocarbonylation

A facile formal synthesis to aphanorphine and its analogue is described, featuring Rh-catalyzed cyclohydrocarbonylation of 2-aminodihydronaphthalene to the bridged benzazepine core. Subsequent introduction of the methyl group and functional group transformation complete the synthesis of aphanorphine and its analogue over eight steps.

Total synthesis of dehaloperophoramidine using a highly diastereoselective Hosomi–Sakurai reaction

Synthesis involving diastereoselective Hosomi–Sakurai reaction to install the contiguous quaternary stereocentres.

Enantioselective Synthesis of Dialkylated α-Hydroxy Carboxylic Acids through Asymmetric Phase-Transfer Catalysis

In the presence of an L-tert-leucine-derived urea-ammonium salt as phase-transfer catalyst, a highly enantioselective alkylation of 5H-oxazol-4-ones with various benzyl bromides and allylic bromides has been developed to furnish catalytic asymmetric synthesis of biologically important dialkylated α-hydroxy carboxylic acids with a broad scope. This is the first example of an L-amino acid-derived urea-ammonium salt being used as a phase-transfer catalyst with excellent catalytic efficiency.