V. V. Druzhinina

Synthesis of O-vinyl ethers of 3-acylindole oximes and their heterocyclization to pyrrolylindoles

O-vinyl ether of 3-acylindole oximes have been synthesized and the possibility has been shown of their thermal conversion into pyrrolylindoles, which permits a heterocyclization mechanism including the stage of [3,3]-sigmatropic shift to be suggested.

Spatial structure of 3-acyl-2-methylindole oximes

It has been established on the basis of the results of 1H and 13C NMR, UV, and IR spectroscopy that 3-acyl-2-methylindole oximes each exist in the form of a mixture of two isomers with a predominance of syn-s-trans form. The proportion of the anti form rises (to 25–35%) with an increase in the volume of the alkyl radical in the oxime grouping.

Structure of 3-acylindole oximes

On the basis of an analysis of the PMR spectra of 3-acylindole oximes it is shown that these compounds, like 3-acylindoles, have an s-trans conformation and exist primarily in the form of syn isomers. The structure of 1-methyl-3-acetylindole s-trans-syn-oxime was confirmed by data from x-ray diffraction analysis.

Synthesis of 3-(2-pyrrolyl)indoles

New 3-(2-pyrrolyl)indole systems were synthesized on the basis of heterocyclization of 3-acylindole oximes with acetylene in a superbase medium (the Trofimov reaction). It is shown that only the anti form of the oxime participates in the formation of the pyrrole ring.

Mass-spectrometric investigation of 3-acylindole oximes

Fragmentation pathways that are due to fragmentation of the oximine grouping and are typical for all of the oximes, and lead to [M-OH]+, [M-NHOH]+, and [M-C(R3)-NOH]+ ions are characteristic for the mass spectra of 3-acylindole oximes. In addition, the presence of a nucleophilic indole ring leads to a number of specific rearrangement processes, particularly to the Beckmann rearrangement.

Three-dimensional structure of 3-acylindoles

On the basis of a comparison of the experimental dipole moments with the calculated values, as well as data from the UV, IR, and PMR spectra, it is shown that 3-acylindoles exist in the form of equilibrium mixtures of the planar S-cis and S-trans conformers with preponderance of the latter.