Akiko Nishida

Stereoselective pyrroline-ring formation through the cyclization of conjugated azomethine ylides at the periphery of pyrido[1,2-a]pyrimidine system

The thermal reaction of N-benzyl-N-[3-(N-substituted imino)methyl-4-oxo-4H-pyrido[1,2-a]pyrimidin-2-yl]amino acid esters, generated from aldehyde esters and primary amines, provides 2,3-dihydropyrido[1,2-a]pyrrolo[2,3-d]pyrimidin-4(1H)-one derivatives effectively and stereoselectively. Therein, the stereoselective generation of conjugated azomethine ylides from the imine esters and their cyclization is essential for the pyrroline-ring formation.

Regioselective bromination of phenols

Abstract Regioselective bromination of phenols gave 2-bromo-, 4-bromo-, 2,6-dibromo-2,4-dibromo, 2-bromo-6-substituted, 4-bromo-2-substituted and 2,4-dibromo-6-substituted phenols, respectively. Especially, 2-bromo-, 2,6-dibromo- and 2-bromo-6-substituted phenols which were prepared via long steps, were obtained in NBS-amine (primary and secondary) system in high yields under ordinary conditions. The scope and their mechanisms were discussed.

Highly selective monotetrahydropyranylation of symmetrical diols catalysed by a strongly acidic ion-exchange resin

Several primary and secondary symmetrical diols, ranging from propane-1,3-diol to decane-1,10-diol, are selectively monoprotected by monotetrahydropyranyl ether formation catalysed by a strongly acidic ion-exchange resin (Dowex 50w × 2, 50–100 mesh) in a 3,4-dihydro-2H-pyran-hydrocarbon mixture.

Conversion of ketals to ketones by nitrogen dioxide in the presence of silica gel

Nitrogen dioxide transforms ketals to ketones in the presence of silica gel under neutral, anhydrous and mild conditions.