Palladium(II)-catalysed formation of indoles from 2,2-diphenyl-2H-azirines

Fe(II)-Catalyzed Amination of Aromatic C−H Bonds via Ring Opening of 2H-Azirines: Synthesis of 2,3-Disubstituted Indoles

“…Thermal rearrangement of 2-aryl-2 H -azirines via vinyl nitrene intermediates6a provides an efficient route to indoles, although it remains in scattered use in indole syntheses (Scheme 1). 6 This rearrangement could be catalyzed by Pd(PhCN) 2 Cl 2 7a or Rh 2 [OC(O)CF 3 ] 4 7b. The catalytic variant of the rearrangement has also received little attention from the chemistry community and only two reports have been published to date 7.…”

“…6 This rearrangement could be catalyzed by Pd(PhCN) 2 Cl 2 7a or Rh 2 [OC(O)CF 3 ] 4 7b. The catalytic variant of the rearrangement has also received little attention from the chemistry community and only two reports have been published to date 7. Although a vinyl nitrene metal complex was speculated to be involved in one of the catalyzed rearrangements, no mechanistic studies were performed 7b.…”

“…The catalytic variant of the rearrangement has also received little attention from the chemistry community and only two reports have been published to date 7. Although a vinyl nitrene metal complex was speculated to be involved in one of the catalyzed rearrangements, no mechanistic studies were performed 7b. Only one example of azaindoles prepared by the thermal rearrangement has been reported4a while the catalyzed process has not been applied to azaindole synthesis.…”

“…2 H -Azirines can be readily prepared from ketones using modified Neber rearrangement processes via hydrazones in three steps developed by Padwa7b,10 or oximes in two steps developed by Taber6b (Scheme 2). Azirine 1a 6b,7 was chosen as the model substrate to study the rearrangement of 2-aryl- 2H -azirines to indoles.…”

Transition Metal‐Catalyzed Formation of N‐Heterocycles via Aryl‐ or Vinyl C–H Bond Amination

“…In 1977, Taniguchi and co-workers reported that 5 mol-% palladium dichloride catalyzed the conversion of triphenylsubstituted azirine 14 into 2,3-diphenylindole at 30°C [Equation (1)]. [7] The authors were able to crystallize the palladium diazirine complex 15, and they attributed the role of the Lewis acidic Pd II to assist in the cleavage of the C-…”