An increase in viscosity in region I arises from a relative decrease of acetone content in the solution, in which polyether segments lose their solvation sheaths and come together forming hydrophobic associates that physically cross-link (2); while the chain extender of diamine derivative that partially performs the chain extension of NCO -- NH reaction, and that is partially blocked by acetone forming a ketimine (acetimine) (21).
This ketimine can be used as a latent chain extender in order to control the NCO -- NH reaction, and can also be existed in a hydrophilic isocyanateterminated prepolymer without a reaction taking place.
[alpha],[beta]-Unsaturated ketimines are chalcone Schiff's bases posses various pharmacological properties [16-18].
Typical procedure for synthesis of [alpha],[beta]-unsaturated ketimines
In continuation of earlier research work devoted towards development of green chemistry and development of new synthetic methodologies in organic chemistry [25] herein, we report a simple, efficient and environmentally benign procedure for synthesis of some new [alpha],[beta]-unsaturated ketimines from condensation of 2-hydroxychalcone with substituted aromatic amines in water suspension with high yields (Scheme 1).
Recently various method have been developed for the synthesis [alpha],[beta]-unsaturated ketimines which involves use of hazardous solvent and costly chemicals/catalyst [19-23].
In conclusion, we have first time reported a simple and efficient synthesis for [alpha],[beta]-unsaturated ketimines from 2-hydroxychalcone and substituted aromatic amines under water suspension.