Regioselective Synthesis of 3-Carbo-5-phosphonylpyrazoles through a One-Pot Claisen-Schmidt/1,3-Dipolar Cycloaddition/Oxidation Sequence
作者:Anthony R. Martin、Kishor Mohanan、Loic Toupet、Jean-Jacques Vasseur、Michael Smietana
DOI:10.1002/ejoc.201100167
日期:2011.6
A one-pot reaction involving an aldehyde, a methyl ketone, and the Bestmann-Ohira reagent has been developed for the synthesis of variously substituted 3-carbo-5-phosphonylpyrazoles. Our synthetic methodology features a domino Claisen- Schmidt/1,3-dipolar cycloaddition/oxidationsequence,which leads to the target compounds in excellent yields. We further demonstrated that this unprecedented sequence
A novel and efficient reaction of vinyl azides with Bestmann-Ohira reagent for the regioselectivesynthesis of phosphonylpyrazoles is presented. Reaction proceeds through 1, 3 dipolar cycloaddition with an excellent yield in short period of time under mild reaction conditions. Moreover, no column purification is involved for the isolation of products.
Bestmann–Ohira reagent. The reaction offers a convenientroute for the synthesis of regioisomerically pure 3,5-disubstituted or 3,4,5-trisubstituted pyrazoles in excellent yields. However, di-ynones and molecules possessing both ynone and enone functionalities provide only monocycloaddition products, whereas another multiple bond undergoes Michaeladdition with the methoxide anion.