Iodine-mediated one-pot synthesis of indoles and 3-dimethylaminoindoles via annulation of enaminones

Abstract

The synthesis of 2-carbonylindoles was achieved via a iodine-mediated cyclization of the corresponding enaminone precursors, which were formed by reaction of the -arylaminomethylene carbonyl derivatives with N,N′-dimethylformamide dimethyl acetal (DMFDMA). An alternative and more efficient procedure consisted of a similar cyclization of the enaminones, but under solvent-free and grinding reaction conditions. In another iodine-promoted procedure, 2-carbonyl-3-dimethylaminoindoles were synthesized via a one-pot cascade reaction between the -arylaminomethylene carbonyl derivative and DMFDMA.

Manganese‐catalyzed Efficient Synthesis of N‐heterocycles and Aminoketones Using Glycerol as a C3 Synthon

“…Full experimental details for preparing catalysts and dehydrogenation coupling reaction, spectroscopic and chromatogramphic data of all compounds, are available in the Supporting Information of this article. The authors have cited additional references within the Supporting Information [53–66] …”

Pyrrole-Based Enaminones as Building Blocks for the Synthesis of Indolizines and Pyrrolo[1,2-a]pyrazines Showing Potent Antifungal Activity

“…The design of pyrrole-containing compounds as potential antifungal agents was based on the evidence that benzofuran [32,33], benzothiophene [34], and indole [35,36] frames (including those of several natural products) can be built through intramolecular cyclization of 2-phenoxy-, 2-thiophenoxy-, and 2-anilino-3-(dimethylamino)propenoates, respectively. The latter derivatives have generically been called enaminones and proven to be versatile substrates in heterocyclic chemistry [37,38].…”

“…When utilizing POCl 3 in DMF at 0 • C, the yield of 5a was 28%, and the conversion of 12b to 5b with this Lewis acid was insignificant. The transformation of 12c to 5c with iodine [36] provided a low yield (18%). Finally, a 1.0 M nitrobenzene solution of AlCl 3 in methylene chloride as the solvent at room temperature efficiently furnished the series 5a-c in variable yields (Scheme 6).…”

Regioselective Mercury(I)/Palladium(II)-Catalyzed Single-Step Approach for the Synthesis of Imines and 2-Substituted Indoles

“…Our group has an ongoing interest in designing and carrying out the novel synthesis of heterocycles [ 69 , 70 , 71 ], and in particular of aza-heterocycles and indoles [ 72 , 73 , 74 , 75 ]. Accordingly, the aim of the present study was to assess the feasibility of preparing indoles in a one-pot process, involving the regioselective Hg(I)-catalyzed hydroamination of terminal alkynes to produce imines as intermediates, and their subsequent Pd(II)-catalyzed cross-coupling oxidative cyclization to afford the corresponding C-2-substituted indoles ( Scheme 1 c).…”

“…The latter regenerates the Hg(II) catalyst by protonolysis to give the enamine, which is converted into the desired imine 5a (Scheme 1a) [53,54]. Our group has an ongoing interest in designing and carrying out the novel synthesis of heterocycles [69][70][71], and in particular of aza-heterocycles and indoles [72][73][74][75]. Accordingly, the aim of the present study was to assess the feasibility of preparing indoles in a one-pot process, involving the regioselective Hg(I)-catalyzed hydroamination of terminal alkynes to produce imines as intermediates, and their subsequent Pd(II)-catalyzed crosscoupling oxidative cyclization to afford the corresponding C-2-substituted indoles In contrast, indoles have been elaborated by diverse protocols [55], such as the wellknown Fischer [56,57], Julia [58], Bartoli [59], and Gassman [60] procedures, each of which include a sigmatropic rearrangement at a high temperature.…”