Visible Light-Mediated <i>In Situ</i> Generation of δ,δ-Disubstituted <i>p</i>-Quinone Methides: Construction of a Sterically Congested Quaternary Stereocenter
Arun Sharma, Vikas Dixit, Sharvan Kumar, Nidhi Jain
Abstract
An unprecedented visible light-assisted and zinc triflate-catalyzed construction of a diaryl-substituted quaternary stereocenter is reported. 2-(4-Hydroxyphenyl)-substituted aldehydes and ketones have been prepared in moderate to high yields via multicomponent reaction of acetylene, benzoquinone (BQ), and indole/aniline/thiol. The reaction is believed to proceed via in situ generation of p-quinone methide through a [2+2] cycloaddition–retroelectrocyclization of BQ and acetylene in blue light followed by a zinc triflate-catalyzed vinylogous Michael addition reaction with nucleophiles.
Topics & Concepts
ChemistryTrifluoromethanesulfonateStereocenterNucleophileSteric effectsZincCycloadditionIndole testMichael reactionIn situAcetyleneQuinoneAnilineOrganic chemistryPhotochemistryMedicinal chemistryCatalysisEnantioselective synthesisSynthesis of Indole DerivativesSulfur-Based Synthesis TechniquesPhotochromic and Fluorescence Chemistry