| Autor: |
Forbes KC; Department of Chemistry, Occidental College, 1600 Campus Road M-5, Los Angeles, California 90041, United States., Crooke AM; Department of Chemistry, Occidental College, 1600 Campus Road M-5, Los Angeles, California 90041, United States., Lee Y; Department of Chemistry, Occidental College, 1600 Campus Road M-5, Los Angeles, California 90041, United States., Kawada M; Department of Chemistry, Occidental College, 1600 Campus Road M-5, Los Angeles, California 90041, United States., Shamskhou KM; Department of Chemistry, Occidental College, 1600 Campus Road M-5, Los Angeles, California 90041, United States., Zhang RA; Department of Chemistry, Occidental College, 1600 Campus Road M-5, Los Angeles, California 90041, United States., Cannon JS; Department of Chemistry, Occidental College, 1600 Campus Road M-5, Los Angeles, California 90041, United States. |
| Abstrakt: |
Photoredox catalysis has become a powerful method to generate free radical intermediates in organic synthesis. This report describes the use of photoredox catalysis to directly oxidize common nucleophilic anions to access electrophilic 1,3-dicarbonyl and amidyl radical intermediates. First, conjugate bases of 1,3-dicarbonyls were oxidized to neutral radical species for intramolecular hydro- and dialkylation of alkenes. This overall redox-neutral process provided cyclopentanone products in excellent yields (up to 96%). The scope included a variety of styrene radical acceptors and products with newly formed vicinal quaternary carbons. This process was then extended to the synthesis of pyrrolidinones by alkene amidoalkylation that proceeded via N -aryl amidyl radical intermediates in good yield (up to 85%). These reactions were characterized by their mild conditions, high atom economy, and the absence of stoichiometric byproducts. Mechanistic and computational studies supported a stepwise proton-coupled electron transfer mechanism, where an "electron borrowing" photocatalyst oxidizes an anion and reduces a benzylic radical after bond formation. |
