Synthesis of 2-(N-disubstituted amino)ethyltriphenylphosphonium bromides

2-(N-Disubstituted amino)ethyltriphenylphosphonium bromides are prepared in quantitative yields with high purity by reacting secondary amines with 2-methoxyethyltriphenylphosphonium bromide under aqueous conditions. The differential reactivity of this reagent offers advantages for the preparation of aminoethyltriphenylphosphonium bromides possessing nucleophiles such as hydroxy groups.     

Kinetics of the alkaline hydrolysis of isatin and N-methylisatin in water and water-N,N-dimethylacetamide mixtures

The kinetics of amide bond cleavage of isatin and N-methylisatin in the presence of N,N-dimethylacetamide (DMA) was followed spectrophotometrically in the range of solvent composition (0–48.53 wt.%) and temperatures (40–70 °C) using piperidine as a nucleophile. The reaction was studied under pseudo-first-order kinetics. The rate of the reaction decreases largely with increasing organic solvent content. The thermodynamic activation parameters were calculated and discussed in terms of solvation of the activated complex. No linearity was observed between log rate constant and the reciprocal dielectric constant for the solvent used suggesting that there is a selective solvation by higher polar solvent (water). Finally, a mechanism for the ring opening for isatin and N-methylisatin was proposed.     

2H-Pyran-2-ones and their annelated analogs as multifaceted building blocks for the fabrication of diverse heterocycles

2H-Pyran-2-ones are widely present in nature and found as either isolated or in fused form. Depending on the fusion of benzene ring, pyran can give coumarins, isocoumarins, dibenzopyrans etc. This class of molecules exhibit excellent biological activity and photophysical properties. Apart from these, 2H-pyran-2-one also acts as very good Michael acceptor, therefore act as very important synthetic precursor. Suitably functionalized 2H-pyran-2-one has been widely explored for their synthetic potential. In this review, we have focused on use of different nucleophiles based on carbon, nitrogen, oxygen and sulfur to generate vast molecular diversity. The functionalized 2H-pyran-2-ones exhibit three electrophilic centres with different electrophilicity. Use of suitable nucleophiles can act on either of the position based on its reactivity to generate new chemical entity. 2H-Pyran-2-one has been explored as precursor for the synthesis of various biologically important nucleuses like pyridine, pyrimidine, quinolines, isoquinolines, fused quinolines, pyrazole, pyrroles, imidazopyridine, thiazole, oxazole, fused and isolated pyrans, coumarins, isocoumarins, benzothiophenes, dibenzohiophenes, dibenzofurans, diazapines, oxahelicines, thia-oxa helicines, and various other heterocycles under base mediated conditions. Use of suitably substituted 2H-pyran-2-one and nucleophile can generate new molecular entity. In this review, we have discussed the properties, synthesis and their synthetic applications to generate various classes of heterocycles.