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

Article abstract of DOI:10.1016/j.tetlet.2011.06.061

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 arylboronic acids.