Synthesis of 1,3,5-Trisubstituted [4-tert-Butyl 2-（5,5-difluoro- 2,2-dimethyl-6-vinyl-l,3-dioxan-4-yl）acetate]pyrazoles via a Pd-Catalyzed C--H Activation

The gem-difluoromethylenated acetonide 2 was efficiently synthesized as new precursor of HMG-CoA reduc- tase inhibitor. Straightforward olefination via Pd-catalyzed C4-H activation of 1,3,5-trisubstituted pyrazoles 1 was proceeded smoothly in the presence of Pd（OAc）2 and AgCO3. This protocol has merits in terms of the improved atomic economy and prevention from the generation of by-products.