Rates of reductive elimination of substituted nitrophenols from the (indol-3-yl)methyl position of indolequinones

Elizabeth Swann, Christopher J. Moody, Michael R. L. Stratford, Kantilal B. Patel, Matthew A. Naylor, Borivoj Vojnovic, Peter Wardman, Steven A. Everett
2001 Journal of the Chemical Society. Perkin Transactions 2 (2001)  
A series of indolequinones bearing substituted nitrophenols on the (indol-3-yl)methyl position was synthesised. The nitrophenol leaving groups were appropriately substituted to give a wide range (4 units) in phenolic pK a value. The rate of reductive elimination of phenoxide anions from the (indol-3-yl)methyl position of semiquinone radicals was dependent upon this pK a , with a decrease in 3.8 pK units shortening the half-life from 28 to 1.5 ms. Only 2,4dinitrophenol (pK a = 3.9) was
more » ... 3.9) was eliminated from an unsubstituted (indol-3-yl)methyl position at a rate that would compete with reoxidation of the radical by oxygen. A nitrothiophenol leaving group was eliminated comparatively slowly and only from the hydroquinone. These studies demonstrate the dependence upon leaving group pK a of the rate of reductive elimination from the (indol-3-yl)methyl position of indolequinones. PERKIN 1340
doi:10.1039/b101842f fatcat:23x3s3m4yfcohb2bbbyxo25qeq