Galla V. Karunakar

Gold-Catalyzed Intramolecular Cyclization of N-Propargylic β-Enaminones for the Synthesis of 1,4-Oxazepine Derivatives.

An efficient and mild one-pot, gold-catalyzed intramolecular cyclization of N-propargylic β-enaminones has been achieved for the generation of 1,4-oxazepine derivatives. This synthetic transformation tolerates a range of substituted N-propargylic β-enaminones in moderate to good yields.

Gold-catalysed cyclisation of N-propargylic β-enaminones to form 3-methylene-1-pyrroline derivatives.

A gold(I) catalysed reaction between N-propargylic β-enaminones and arynes was developed to access 3-methylene-1-pyrrolines. The title compounds were obtained in 57-78% yields. This reaction is useful for the generation of substituted 1-pyrrolines exhibiting significant molecular complexity.

Reaction of N-propargylic β-enaminones with acetylene dicarboxylates: catalyst-free synthesis of 3-azabicyclo[4.1.0]hepta-2,4-dienes

3-Azabicyclo[4.1.0]hepta-2,4-dienes were efficiently synthesized in a reaction of N-propargylic β-enaminones with acetylenedicarboxylates under novel and exceptional catalyst- and base-free conditions in a single step.

Oxidative coupling of 2-naphthol to (R)/(S)-BINOL by MCM-41 supported Mn-chiral Schiff base complexes

Three Mn(III)-chiral Schiff base complexes supported on MCM-41 are found to be effective reusable catalysts for enantioselective oxidation of 2-naphthol to (R)- and (S)-BINOL (1,1′ bi-2-naphthol) in the presence of oxygen. The supported Mn(III)-complexes are characterized by PXRD, FTIR, solid state-NMR, BET, and cyclic voltammetry study. The homo-coupling reaction with oxygen as the oxidant is promoted by 20 mg of Mn(III) Schiff base complexes to afford binaphthols in nearly quantitative yields with high enantioselectivity of up to 91% ee. The catalytic activities of the homogeneous and heterogeneous chiral catalyst are found to be almost similar. However, the heterogeneous counterparts are found to be advantageous in terms of recyclability and storability. Oxygen partial pressure, the nature of the solvent, temperature and the amount of catalyst affect the catalytic oxidation process. High temperature and highly polar solvent are found to have adverse effects on the catalytic oxidation process.