Divergent synthesis of withasomnines via synthesis of 4-hydroxy-1H-pyrazoles and Claisen rearrangement of their 4-O-allylethers

H Ichikawa, R Watanabe, Y Fujino, Y Usami

Index: Ichikawa, Hayato; Watanabe, Ryo; Fujino, Yuiko; Usami, Yoshihide Tetrahedron Letters, 2011 , vol. 52, # 34 p. 4448 - 4451

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Citation Number: 20

Abstract

4-Hydroxypyrazoles were synthesized by the alkaline hydrolysis of the Baeyer–Villiger oxidation products of 4-formylpyrazoles. This new synthesis of 4-hydroxypyrazoles was applied to the divergent synthesis of withasomnine alkaloids in a unique strategy, for which the key steps included the regioselective Claisen rearrangement of their 4-O-allyl-4-hydroxy- 1H-pyrazoles and a Suzuki coupling of 4-trifluoromethanesulfonyloxy-1H-pyrazoles and ...