Acid-catalyzed isomerization of 3-indolyl sulfides to 2-indolyl sulfides: first synthesis of 3-unsubstituted 2-arylthioindoles. Evidence for a complex intermolecular process
摘要:
The acid-catalyzed isomerization of 3-indolyl sulfides 1 to the corresponding 2-indolyl sulfides 4 provides the first synthesis of 3-unsubstituted 2-(arylthio)indoles, a hitherto unattainable class of compounds. When catalyzed by trifluoroacetic acid, the isomerization proceeds mainly via an intermolecular mechanism involving initial disproportionation to a 2,3-indolyl bis-sulfide 5 and an unsubstituted counterpart 6 followed by further interaction of these species to yield the rearranged isomer 4. A mechanism is proposed involving a role for the acid in the sulfenyl-transfer steps. This type of process also occurs, to a lesser extent, in the polyphosphoric acid catalyzed isomerization.
Unexpected acid-catalysed rearrangement of certain 3-(arylthio)indoles to 2-(2-aminophenyl)benzothiophenes
作者:Pierre Hamel、Yves Girard、Joseph G. Atkinson、Michael A. Bernstein
DOI:10.1039/c39900001072
日期:——
3-(Arylthio)indoles (1), in which the aryl group is an electron-rich ring system, undergo a novel structural rearrangement to 2-(2-aminophenyl)benzothiophenes (2) upon heating in polyphosphoric acid.