Electrosynthesis of nitrogen heterocycles using environmentally friendly methodologies

Abstract

Cyclic voltammetry and constantcurrent electrolysis in a one-compartment cell with a sacrificial anode has been used to study the indirect electroreduction of N-allyl-haloamides by electrogenerated Ni(I) complexes conducted in N,N-dimethylformamide (DMF) and acetonitrile (ACN) and the results were compared with those obtained in protic solvents such as EtOH and EtOHH 2 O mixtures. It was observed that the indirect electrochemical reduction of N-allyl--haloamides led to the corresponding lactams and the yields and selectivities obtained in EtOH and EtOHH 2 O were much better than those obtained in DMF or ACN.

Electroreductive Remediation of Halogenated Environmental Pollutants

“…Electrogenerated nickel(I) cyclam and nickel(I) tetramethyl cyclam have been employed to carry out a variety of reductive cyclization reactions involving allyl 2-halophenyl ethers, 177 propargyl and allyl bromoesters, 178−181 and N-allyl-α-haloamides. 182 Espenson and co-workers used these catalysts to reduce alkyl halides 183 and some α,ω-dihaloalkanes. 184,185 With this same class of catalysts, Ozaki et al accomplished a number of interesting electrosyntheses: (a) intramolecular cyclization of nallylic and n-propargylic α-bromoamides and of o-bromoacryloylanilides to give five-membered lactams; 186 (b) stereoselective addition of n-, sec-, and tert-butyl radicals to αmethylenebutyrolactones; 187 Electrogenerated nickel(I) tetrapyrrole complexes have been shown to catalyze the reductions of dichloromethane and methyl iodide, 193 alkyl halides, 194 and aryl halides.…”

Use of Electrochemistry in the Synthesis of Heterocyclic Structures

“…Electroreduction of organic halides or related substrates, − ketones, − aromatic imines, − cyclic imides, − can generate carbon-centered radicals, which could be trapped by internal π-bond systems that tethered a heteroatom leading to the formation of heterocycles.…”

“…In 2009, Medeiros and co-workers found that Ni­(tmc)­Br 2 was also an effective catalyst for electroreductive cyclization of N -allyl-α-haloamides (Scheme ). When N -allyl- N -methyl-2-bromoethanamide 50 was employed as a substrate, cyclic product 51 was furnished in 18% yield; cyclized products 53 and 54 were obtained in 53% total yield from the electroreductive cyclization of 52 . These reactions were accomplished in a single-compartment cell equipped with a sacrificial magnesium anode and a carbon fiber cathode using n- Bu 4 NBF 4 as the supporting electrolyte.…”

The Fascinating Chemistry of α‐Haloamides

“…Later, Medeiros and co‐workers obtained better results in terms of yields and selectivities by conducting the electrosyntheses in “green” solvents such as EtOH and EtOH‐H 2 O mixtures …”