Thermal rearrangement of v-triazolo[1,5-a]pyridine-3-acraldehydes into 3-methyl-5-(2-pyridyl)pyrazoles

Abstract

The cis-v-triazolo[1 5-a]pyridine-3-acraldehyde (2) undergoes thermal rearrangement to 3-methyl-5-(2-pyridyl)-pyrazole-4-carbaldehyde (4); 3-methyl-5-(2-pyridyl)pyrazole (7) is also produced. The trans-acraldehyde (3) gives only the pyrazole (7). Conversion of the aldehyde (4) into the pyrazole (7), and a synthesis of the pyrazole (7) are described. A mechanism for the rearrangement is suggested.