Regioselective Synthesis of Sulfonylpyrazoles via Base Mediated Reaction of Diazosulfones with Nitroalkenes and a Facile Entry into Withasomnine
作者:Rahul Kumar、Irishi N. N. Namboothiri
DOI:10.1021/ol201534f
日期:2011.8.5
A base mediated reaction of alpha-diazo-beta-ketosulfone with nitroalkenes affords sulfonylpyrazoles as single regioisomers in excellent yield in a one-pot room temperature reaction. Aryl, heteroaryl, styrenyl, alkyl, hydroxymethyl, and hydrazinyl groups could be introduced on the pyrazole ring by the appropriate choice of nitroalkenes. Synthesis of sulfonylpyrazole fused to other heterocycles and application of the methodology to an expedient synthesis of a pyrazole alkaloid, Withasomnine, are also reported.
Synthesis of Withasomnines and Their Non-natural Analogues from Aldehydes and 4-Nitro-1-butanol in Three Steps
作者:Deepti Verma、Rahul Kumar、Irishi N. N. Namboothiri
DOI:10.1021/jo400207u
日期:2013.4.5
Total synthesis of all three pyrazole-based withasomnine alkaloids and selected examples of their non-natural analogs has been achieved from readily available aldehydes and 4-nitro-1-butanol in three steps. Since 4-nitro-1-butanol in turn is prepared in two steps via Michael addition of nitromethane to acrylate followed by borane reduction of the ester group and the key 1,3-dipolar cycloaddition step