A. F. Vaisburg

Vicinal Heteroaromatic Hydroxy, Mercapto and Hydroseleno Aldimines. Synthesis, Structure, Properties

Abstract This review is devoted to the latest achievements in the chemistry of vicinal heteroaromatic hydroxy, mercapto and hydroseleno aldimines. The synthesis, structure and reactivity of the above compounds are presented and discussed.

Chemistry of hydroxy, mercapto, and selenolo aldimines of the heteroaromatic series (review)

The review is devoted to the modern state of the chemistry of o-substituted hydroxy, mercapto, and selenolo aldimines of the heteroaromatic series. Data on methods of synthesis and the reactivities of the aldimines are presented. Some problems involving the structure of these compounds are examined.

Condensed heterocycles. 48. Benzo[b]furan mercapto- and selenolaldehydes in the synthesis of bifunctional and complex-forming compounds

Abstract2-Bromo-3-benzo[b]furaldehyde and 3-chloro-2-benzo[b]furaldehyde react with sodium hydrosulfide or hydroselenide to give isomeric mercapto- and selenolbenzo furaldehydes, which afford the S (or Se) alkyl derivatives on reaction with ethyl chloroacetate, and Schiff bases on reaction with ethylenediamine hydrochloride. In the presence of sodium ethoxide, the S- and Sealkylated mercapto- and selenolaldehydes cyclize to thieno- and selenobenzofurans, while the Schiff bases afford chelate complexes with nickel and copper acetates.

Condensed heterocycles 47. Intramolecular hydrogen bonding in heteroaromatic hydroxy-, mercapto-, and selenolaldimines

Examination of the PMR spectra of benzo[b]furan and benzo[b]thiophene hydroxy-,mercapto-, and selenolaldimines, obtained in different solvents, show the absence of any correlation between the chemical shifts of the NH protons in aldimines and the strength of the intramolecular hydrogen bond (IMHB) NH...X (X = O, S, or Se). Novel condensed thio- and selenopyrans have been obtained from these aldimines and acrylonitrile. The conditions for the reaction are shown to depend on the strength of the IMHB in the aldimines.

Condensed heterocycles. 46. Crystal structure of 3-mercapto-2-benzo[b]-furylidene-(p-methylphenyl) amine

An x-ray structural examination of 3-mercapto-2-benzo [b] furylidene-(p-methyl-phenyl) amine has been carried out. For the first time, the position of the bridge hydrogen atom in a mercaptoaldimine containing the planar conjugated S=C-C=C-N grouping closed by an intramolecular N-H...S hydrogen bond has been established.

Condensed heterocycles. 45. Synthesis and structures of imines of 2-selenolo-3-benzo [b] furanaldehyde and 3-selenolo-2-benzo [b] furanaldehyde and their derivatives

A number of new selenolaldimines of benzo [b] furan were synthesized. It was established that they exist in dipolar form with delocalized multiple bonds.

Condensed heterocycles. 44. Synthesis and structure of imines of 2-mercaptobenzo[b]-furan-3-carbaldehydes and 3-mercaptobenzo[b]furan-2-carbaldehydes and their derivatives

A number of isomeric mercapto aldimines of benzo[b]furan have been obtained and their structure and properties have been studied in comparison with their benzo[b]-thiophene analogs. It has been shown that the nature of the heterocycle has no substantial influence on the structure and properties of these compounds, in contrast to the initial mercapto and hydroseleno aldehydes. It has been observed that the 2-mercapto or 2-methylthio(methylseleno) groups in benzo[b]furan-3-carbaldehydes are readily replaced by an amino group, while they are not replaced in the isomeric 3-mercapto- and 3-methylthio(methylseleno)benzo[b]furan-2-cabaldehydes.

Condensed heterocycles. 42. Synthesis and some properties of 3-hydroselenobenzo[b]furan-2-carbaldehyde and 2-hydroselenobenzo[b]furan-3-carbaldehyde

The reactions of 3-chlorobenzo[b]furan-2-carbaldehyde and 2-bromobenzo[b]furan-3-carbaldehyde with sodium hydrogen selenide have yielded isomeric hydroseleno aldehydes which, under the action of atmospheric oxygen, have oxidized to diselenides, while alkylation of the seleno aldehydes with methyl iodide leads to the formation of the corresponding methylseleno derivatives.