Microwave Activation of Reaction between 1,3,5-Trisubstituted Pyrazole-4-carbaldehydes and Sterically Hindered Aminoalcohols

Abstract

Structure of products of reaction between 1,3,5-trisubstituted pyrazole-4-carbaldehydes and 2-aminoalkan-1-oles is determined by the structure of the alkyl chain of aminoalcohol. The reaction with 2-aminobutan-1-ol proceeds for 2 h in conditions of microwave activation at 150°C with the formation of 2-hydroxyalkylimines of pyrazole-4-carbaldehyde. At reaction of 1,3,5-trisubstituted pyrazole-4-carbaldehydes with 2-amino-2-methylpropan-1-ol mixtures form of the corresponding 2-hydroxyalkylimines and pyrazol-4-yl-1,3-oxazolidines in ratios 66 : 33–80 : 20. Heating of 2-hydroxyalkylimines of pyrazole-4-carbaldehyde in the presence of dehydrating agents, in particular, trimethylchlorosilane, does not result in 1,3-oxazolidines.