Catalyst‐Free One‐Pot Tandem Reduction of Oxo and Ene/Yne Functionalities by Hydrazine: Synthesis of Substituted Oxindoles from Isatins

Abstract

An unprecedented one‐pot tandem reduction of oxo and ene/yne functionalities of substituted isatins is disclosed for the synthesis of oxindole derivatives in excellent yields. The reaction is simply performed by treating N‐(2‐alkenyl)/propargylisatins with an excess amount of hydrazine hydrate (25 %) under catalyst‐free refluxing conditions. The reduction process appears to be quite unique and proceeds quite efficiently without the aid of any catalyst at ambient pressure.

Design and development of dithienopyrrolobenzothiadiazole‐isoindigo based conjugated polymers and their hole mobilities

“…The formylated DTPBT ( 1 ) was synthesized from 1,2‐phenylene diamine using the reported procedure by following the literature procedure (Scheme S1). 34 The synthesis of 5‐bromo‐ N ‐ethylhexylindoline‐2‐one ( 2 ) was carried out from 5‐bromoisatin according to the literature procedure (Scheme ) 35–37 . The π‐extended‐isoindigo ( 3 ) was synthesized by Knoevenagel condensation reaction between compound 1 with 2 in the presence of piperidine in acetonitrile/chloroform solvent (Scheme 1).…”

“…34 The synthesis of 5-bromo-N-ethylhexylindoline-2-one (2) was carried out from 5-bromoisatin according to the literature procedure (Scheme S2). [35][36][37] The π-extended-isoindigo (3) was synthesized by Knoevenagel condensation reaction between compound 1 with 2 in the presence of piperidine in acetonitrile/chloroform solvent (Scheme 1).…”

Zinc-Catalyzed Alkyne–Carbonyl Metathesis of Ynamides with Isatins: Stereoselective Access to Fully Substituted Alkenes

“…Metal catalysts used in this reaction were purchased from commercial sources and used without further purification. Isatin derivatives were prepared according to a previously published procedure and had physical and spectral properties identical to those earlier reported . Flash column chromatography was performed using silica gel (300–400 mesh).…”

Extended isoindigos as building blocks for developing D–A-type conjugated polymers

“…n-Tetradecylindolin-2-one (2) is synthesized according to the reported literature process. [54][55][56] Dialdehyde 4 is synthesized from 1,4-dihydroxybenzene according to the literature procedure reported by Doddi et al 57 The p-extended isoindigo derivatives with p-dimethylenebenzene, dialkoxy-p-dimethylenebenzene and 2,5-dimethylenethiophene as the central spacer (3, 5 and 7) are synthesized by Knoevenagel condensation 58 between n-tetradecylindolin-2-one (2) and the corresponding dialdehydes (1, 4 and 6) using piperidine as a base (Scheme 1). D-A-type p-conjugated polymers are synthesized via C-C coupling reaction in which the 5,5 0 -bis(trimethylstannyl)-2,2 0bithiophene unit is coupled with p-extended isoindigo compounds 3, 5 and 7 using Pd 2 (dba) 3 and tri-o-tolylphosphine as the catalyst-ligand system in refluxing toluene (Scheme 2).…”