On the electron transfer and hydrogen atom abstraction mechanism for 1-benzyl-1,4-dihydronicotinamide reduction of benzoquinones

Abstract

This paper is dedicated to Professor Ross Stewart on the occasion of his 65th birthday DENNIS D. TANNER, ABDELMAJID KHARRAT, and H. OUMAR-MAHAMAT. Can. J. Chem. 68, 1662 (1990). The reduction of p-benzoquinone (BQ) by 1-benzyl-l,4-dihydronicotinamide (BNAH) proceeds by a free-radical chain mechanism initiated by single electron transfer (SET). In dry deoxygenated acetonitrile, the chain, whose propagation steps contain a SET-hydrogen atom transfer sequence, could be inhibited by diitrobenzene and initiated by di-tert-butylperoxyoxalate. The reduction does not follow second-order reaction kinetics. The fractional order of each reactant was found to be 0.80 and 1.36 for BNAH and BQ, respectively. The AGO values for both the initiation and the propagation steps were evaluated electrochemically (CV) and were found to be of a reasonable magnitude to sustain a free-radical chain process.

Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis

“…This radical is then believed to undergo a second single-electron reduction followed by protonation to give dimethyl succinate ( 3 ). The single-electron donor for this step may be another equivalent of Ru(bpy) 3 + , or it may be dihydropyridyl radical 7 , the product of deprotonation of radical cation 4 and itself a strong reductant ( E 1/2 red = −0.94 V vs SCE) . Upon loss of an electron, radical 7 is converted to pyridinium 8 , the ultimate product of two-electron oxidation of BNAH.…”