Facile access to bis(indolyl)methanes by copper-catalysed alkylation of indoles using alcohols under air

Synthesis of Bis(3‐indolyl)methanes Mediated by Potassium tert‐Butoxide

“…Both work-up protocols afforded the product with same yields. [42] Purification: silica gel, Hexane/AcOEt (6 : 1) with gradient; PTLC, Hexane/AcOEt (6 : 1) with gradient; Yield: 77 % (31.7 mg); red oil; [43] Purification: silica gel, Hexane/AcOEt (6 : 1) with gradient; PTLC, Hexane/AcOEt (6 : 1) with gradient; Yield: 52 % (20.5 mg); red oil; [44] Purification: silica gel, Hexane/AcOEt (6 : 1) with gradient; PTLC, Hexane/AcOEt (6 : 1) with gradient; Yield: 40 % (14.1 mg); red oil;…”

“…[14] Other examples also include the use of metal-free oxidative reactions. [15,16] Recently, several examples have been reported using aryl amines (1), [17] aldehydes (2), [18][19][20][21][22] ketones (3), [23,24] benzyl amines (4) [16,25] and benzyl alcohols (5) [26][27][28] as starting materials (Scheme 1).…”

Cobalt-catalysed CH-alkylation of indoles with alcohols by borrowing hydrogen methodology

“…24 Afterwards, reports on the C3-alkylation of indoles were presented with Ru-, 25–28 Ir-, 25,29–32 Pd-, 26,33,34 Rh-, 25 and Pt- 35 complexes as catalysts. In addition, homogeneous Fe-, 36–42 Mn-, 43 Ni- 44,45 and Cu- 20,46–49 complexes have been reported to be effective in the C3-alkylation of indole. In contrast, in heterogeneous catalysis only Pt-based materials have been reported.…”

Orthometallated Pd(ii) C^N^S pincer complex catalyzed sustainable synthesis of bis(indolyl)methanesviaacceptorless dehydrogenative coupling of alcohols

“…33 Langer and co-workers reported BIMs by using a 5 mol% Cu(OAc) 2 catalyst at 100 °C temperature. 34 With the aid of excess Mn (5 mol%) catalyst loading, Balaraman and colleagues described the generation of BIMs from aromatic alcohols. 35 Though Srimani et al portrayed site specific indole alkylation and BIM fabrication directly from indoles and alcohols, the catalytic reaction necessitated a higher catalyst loading (5 mol%) at a higher temperature (135 °C), with a relatively longer reaction time (36 h) (Scheme 1).…”