Electroreductive cyclization reactions of 6-chloro-1-phenyl-1-hexyne and 6-chloro-1-phenyl-1,2-hexadiene at a mercury cathode in dimethylformamide

Direct electrochemical reduction of a bromo-propargyloxy ester at vitreous carbon cathodes in dimethylformamide

“…Several reports [10][11][12][13][14] have dealt with electrochemical reduction and intramolecular cyclization of acetylenic halides. Electrolysis of 6-chloro-1-phenyl-1-hexyne at low concentrations (<1 mM) at a mercury cathode [10] proceeds via reduction of the carbon-carbon triple bond, eventually to yield benzylidenecyclopentane.…”

“…Electrolysis of 6-chloro-1-phenyl-1-hexyne at low concentrations (<1 mM) at a mercury cathode [10] proceeds via reduction of the carbon-carbon triple bond, eventually to yield benzylidenecyclopentane. However, at higher concentrations (>2 mM), the same acetylenic chloride undergoes extensive electrolytically induced, base-catalyzed rearrangement to 6-chloro-1-phenyl-1,2-hexadiene which can be reduced to afford several carbocyclic and acyclic products.…”

Electrochemistry of substituted salen complexes of nickel(II): Nickel(I)-catalyzed reduction of alkyl and acetylenic halides

“…This species was encountered in an earlier study [19] of the electroreductive intramolecular cyclization of 6-chloro-1-phenyl-1-hexyne at a mercury cathode in DMF containing 0.10 M tetra-n-butylammonium perchlorate; for that system, the acetylenic chloride was proposed to undergo base-catalyzed isomerization to 6-chloro-1-phenyl-1,2-hexadiene, with the latter phenylconjugated allene being reduced to a radical-anion which cyclizes with expulsion of chloride ion to afford a cyclic allyl radical that can be further reduced and then protonated by the medium to give either benzylidenecyclopentane or (cyclopentenylmethyl)benzene. In the present investigation, several pathways leading to (cyclopentenylmethyl)benzene can be proposed.…”

“…A solution of 1-bromo-5-decyne, tri-n-butyltin hydride, and 1.8 mol% of 2,2 0 -azobis(2-methylpropionitrile) (AIBN) in benzene was refluxed for 36 h, after which the product was purified by reduced-pressure distillation (50°C at 4 torr) and its identity was confirmed with the aid of GC-MS and 1 Benzylidenecyclopentane and (cyclopentenylmethyl)benzene were synthesized by means of a procedure reported by Michaely [18,19]. To a solution of cyclopentyllithium, prepared via the reaction between cyclopentyl bromide and lithium wire in dry tetrahydrofuran and cooled in an ice bath under argon, freshly distilled benzaldehyde was slowly added, and the resulting solution was stirred for 1 h. A saturated aqueous solution of ammonium chloride was added, and the organic phase was washed with water and dried over anhydrous magnesium sulfate; removal of the solvent by means of rotary evaporation gave crude cyclopentylphenyl carbinol.…”

Electrochemical Oxidation and Reduction of Allenes

“…Recently, Pattenden and Robertson [50] have shown an interesting reductive cyclization of terminal allenic nonconjugated ketones. They succeeded in the annulation of five-and six-membered rings (73) to form fused systems (74) with a bridgehead hydroxyl group: In an attempt to perform electroreductive cyclization, Peters and co-workers [49] reduced 6-chloro-lphenyl-l,2-hexadiene (60) (initially formed by a rapid base isomerization of 6-chloro-l-phenyl-l-hexyne) at mercury in DMF. Controlled potential electrolysis of 60 at slightly more negative potentials than its reduction half-wave potential at -2.30 vs SCE produced nine products at the following distribution: three five-membered ring compounds; l-benzylcyclopentene (6 I, 37%), benzylidenecyclopentane (62, 29%), benzylcyclopentane (63, 14%) (major products); one four-membered ring compound: trans-l-phenyl-z-cyclobutylethene (64, 9%); two six-membered ring derivatives: l-phenylcyclohexene (65, 3%) and 3-phenylcyclohexene (66, 2%); three open-chain products, 58, 2%; 56, 1% and trans-lphenyl-l,S-hexadiene (67, 3%).…”