Application of nucleophilic substitution of hydrogen in nitroarenes to the chemistry of indoles

The 6π-azaelectrocyclization of azatrienes. Synthetic applications in natural products, bioactive heterocycles, and related fields

Covering: 2006 to 2018 The application of the 6π-azaelectrocyclization of azatrienes as a key strategy for the synthesis of natural products, their analogs and related bioactive or biomedically-relevant compounds (from 2006 to date) is comprehensively reviewed. Details about reaction optimization studies, relevant reaction mechanisms and conditions are also discussed.

Transition-metal-free [3 + 3] annulation of indol-2-ylmethyl carbanions to nitroarenes. A novel synthesis of indolo[3,2-b]quinolines (quindolines)

Indol-2-ylmethyl carbanions stabilized by alkoxycarbonyl, cyano or benzenesulfonyl groups react with nitroarenes to form σ^H-adducts, which in the presence of base (triethylamine or DBU) and trimethylchlorosilane transform into indolo[3,2-b]quinoline derivatives in moderate to good yields.

A general and convenient method for the synthesis of 2,4-dinitrobenzyl ketones. Almost unlimited access to 2-substituted 6-nitroindoles from 2,4-dinitrotoluene and aldehydes

Starting from 2,4-dinitrotoluene and aldehydes, 2-substituted 6-nitroindoles with alkyl, cycloalkyl, aryl and heteroaryl (thienyl, furyl, pyridyl) substituents in the 2-position of the indole ring were synthesized. This methodology can be used for synthesis of indoles with non-racemic substituents.

Nucleophilic C–H functionalization of arenes: a new logic of organic synthesis

Direct metal-free C–H functionalization of arenes with nucleophiles is a new chapter in the chemistry of aromatics. Comprehensive studies on nucleophilic substitution of hydrogen in arenes (the SNH reactions), including mechanisms, intermediates, mathematic and electrochemical modeling, kinetics, electron-transfer, etc. have shown that this is not the hydride ion, but C–H proton is departed, and this process is facilitated by the presence of an appropriate oxidant or an auxiliary group. The SNH reactions, as a part of the general C–H functionalization concept, change the logic of organic synthesis. They open new opportunities, avoiding incorporation of good leaving groups or other auxiliaries in an aromatic ring, as a prefunctionalization step, thus providing a better correspondence to the principles of green chemistry.

Transition-metal-free synthesis of 3-(1-pyrrolidinyl)quinolines and 3-(1-pyrrolidinyl)quinoline 1-oxides via a one-pot reaction of 3-(1-pyrrolidinyl)crotonates with nitrobenzenes

A carbanion of tert-butyl 3-(1-pyrrolidinyl)crotonate adds to nitrobenzenes to form σ^H-adducts, which in the presence of pivaloyl chloride and triethylamine are converted into 3-(1-pyrrolidinyl)quinolines or 3-(1-pyrrolidinyl)quinoline 1-oxides depending on the nitrobenzene structure. This is the first methodology in which a quinoline ring is constructed from a substrate bearing a pyrrolidinyl ring. Starting from optically pure enamines, the method allows synthesis of the corresponding chiral products without racemisation.

Simple synthesis 11-substituted norcryptotackieine derivatives

11-Substituted indolo[2,3-b]quinolines were obtained in reactions ofN-protected indol-3-yl-acetonitrile, -acetate, and -methylsulfone with nitrobenzene derivatives in presence of base and trialkylchlorosilanes.