The Unexpected Desulfurization of 4-Aminothiophenols

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Journal titleJournal Of Organic Chemistry
Pages23792386; # of pages: 8
AbstractThermolysis of 4-aminophenyl benzyl sulfide at 523 K in the hydrogen donor solvent (HDS), 9,10-dihydroanthracene (AnH2), gave 4-aminothiophenol and toluene as the predominant products of the homolytic S-C bond cleavage. Under these conditions, a portion of the 4-aminothiophenol was desulfurized to aniline with first-order kinetics and with a rate constant estimated by kinetic modeling to be 7.0 ? 10-6 s-1. Starting with 4-NH2C6H4SH at 523 K, it was found that sulfur loss was more efficient in the non-HDSs, anthracene and hexadecane, than in AnH2. Under similar (competitive) reaction conditions, YC6H4SHs with Y = H, 4-CN, and 3-CF3 were completely inert; with Y = 4-CH3O, there was some very minor desulfurization, whereas with Y = 4-N(CH3)2 and 4-N(CH3)(H), the sulfur extrusions were as fast as that for Y = 4-NH2. We tentatively suggest that this apparently novel reaction is a chain process initiated by the bimolecular formation of diatomic sulfur, S2, followed by a reversible addition of ground state, triplet 3S2 to the thiol sulfur atom, 4-NH2C6H4S(SS)H, and insertion into the S-H bond, 4-NH2C6H4SSSH. In a cascade of reactions, aniline and S8 are formed with the chains being terminated by reaction of 4-NH2C6H4S(SS)H with 4-NH2C6H4SH. Such a reaction mechanism is consistent with the first-order kinetics. That this reaction is primarily observed with 4-YC6H4SH having Y = N(CH3)2, N(CH3)(H), and NH2 is attributed to the fact that these compounds can exist as zwitterions.
Publication date
AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences
Peer reviewedNo
NPARC number12329136
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Record identifier9a552764-4035-4f32-893f-f968e365255b
Record created2009-09-10
Record modified2016-05-09
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