A general and efficient synthesis of pyrazoles catalyzed by Sc(OTf)3 under solvent-free conditions

pyrazoles were prepared in excellent yields via solventless condensation of various 1,3-diketones (r1cochxcoch3, r1 = me, ph; x = h, me, cl) and hydrazines, acylhydrazines or sulfonyl hydrazines in the presence of a catalytic amount of sc(otf)3 at room temperature. additionally, the catalyst could be recovered easily after the reactions and reused without evident loss in activity.