The aldol reaction of 1-acyl-3,5-dimethylpyrazoles (1) was kinetically
controlled with syn stereoselectivity through lithium enolate interme
diate using LDA. On the contrary, the anti stereoselective aldol react
ion of 1 was caused by the action of DIEA in the presence of MgBr2 und
er the thermodynamic control. in the formation of syn-aldol products u
sing 3-phenyl-1-menthopyrazole as a chiral auxiliary, the diastereosel
ectivity was observed up to 81% de with the predominant configuration
of 2'S form.