Guobin Ma

Enhancement of Neighbouring-Group Participation in Cu-0-Promoted Cross-Coupling gem-Difluoromethylenation of Aryl/Alkenyl Halides with 1,3-Azolic Difluoromethyl Bromides

A copper(0)-promoted direct reductive gem-difluoromethylenation of unactivated aryl or alkenyl halides with benzo-1,3-azolic (oxa-, thia- or aza-) difluoromethyl bromides or 2-bromodifluoromethyl-1,3-oxazoline has been developed for the construction of pharmaceutically important gem-difluoromethylene-linked twin molecules. The unique π-conjugated aryl-fused 1,3-azolic moiety in difluoromethyl bromide substrates could stabilise the reaction intermediates, which promotes the reactivities, providing facile access to the cross-coupling products in good to excellent yields, and allowing significant functional group tolerance. The reaction exhibits an enhanced neighbouring-group-participation effect. This method could provide a new strategy for the construction of gem-difluoromethylene-linked identical or nonidentical twin drugs through further functionalisation of 1,3-azolic skeletons.

Asymmetric aldol reaction organocatalyzed by bifunctional N-prolyl sulfinamides under solvent-free conditions

A class of chiral bifunctional N-prolyl sulfinamide and its TFA salts were prepared and proven to be effective for catalyzing the aldol reaction under solvent-free conditions. In general, the corresponding aldol adducts were obtained with high to excellent yields, and satisfactory diastereo-selectivities and enantioselectivities. A matching effect between chiral proline and sulfinamide moieties was observed in the catalysts. The enantioswitching of both enantiomers in the asymmetric aldol synthesis is found to be dominated by the prolyl moiety.

A facile total synthesis of drospirenone isomers containing 14β-hydrogen configuration.

A facile strategy for the preparation of two isomeric drospirenones 13 and 16 possessing a 14β-hydrogen was developed, using 3β-hydroxyandrost-5-en-17-one as the starting material. The total synthetic route involves eight steps, giving 2% overall yield. The structures of the main compounds 11, 13, 14 and 16 were determined by single crystal XRD analysis.