STEREOCONTROLLED ALDOL REACTION OF N-ACYLPYRAZOLES WITH ALDEHYDES USING LDA OR MGBR2-DIEA

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.