Electrochemical reduction of (+)-(2S,4S)-2,4-dibromopentane
About: This article is published in Journal of Organic Chemistry.The article was published on 1973-11-01. It has received 32 citations till now.
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TL;DR: The results demonstrate that absolute configurations of alkanes can be reliably assigned by using B3LYP/aug-cc-pVDZ TDDFT/GIAO calculations if, but only if, [alpha](D) is significantly greater than 25.
Abstract: The recently developed Gauge-Invariant (Including) Atomic Orbital (GIAO) based Time-Dependent Density Functional Theory (TDDFT) methodology for the calculation of transparent spectral region optical rotations of chiral molecules provides a new approach to the determination of absolute configurations. Here, we discuss the application of the TDDFT/GIAO methodology to chiral alkanes. We report B3LYP/aug-cc-pVDZ calculations of the specific rotations of the 22 chiral alkanes, 2−23, of well-established Absolute Configuration. The average absolute deviation of calculated and experimental [α]D values for molecules 2−22 is 24.8. In two of the molecules 2−23, trans-pinane, 10, and endo-isocamphane, 13, the sign of [α]D is incorrectly predicted. Our results demonstrate that absolute configurations of alkanes can be reliably assigned by using B3LYP/aug-cc-pVDZ TDDFT/GIAO calculations if, but only if, [α]D is significantly greater than 25. In the case of (−)-anti-trans-anti-trans-anti-trans-perhydrotriphenylene, 1, [...
70 citations
TL;DR: In this paper, the reaction between stoichiometric amounts of 1,6-dihalohexanes and electrogenerated nickel(I) salen in dimethylformamide containing 0.10 M tetramethylammonium tetrafluoroborate affords cyclohexane in up to 78% yield.
Abstract: Reaction between stoichiometric amounts of 1,6-dihalohexanes and electrogenerated nickel(I) salen in dimethylformamide containing 0.10 M tetramethylammonium tetrafluoroborate affords cyclohexane in up to 78% yield. Arising via a radical pathway, an ω-haloalkylnickel(II) species is a proposed intermediate for these reductions in which alkanes, 1-alkenes, and aldehydes are also produced. In cyclic voltammetric studies at scan rates of 5-25 mV s - 1 , formation of a passivating film on the surface of the carbon cathode has a dramatic effect on the catalytic reduction of 1,6-dihalohexanes, but this electrode fouling can be overcome by addition of acetic acid to the medium. For controlled-potential electrolyses involving the reduction of a 1,6-dihalohexane with catalytic amounts of electrogenerated nickel(I) salen in the presence of excess acetic acid, most of the substrate is converted into three different esters (hexyl acetate, 1,6-diacetoxyhexane, and dodecyl acetate) which arise via nucleophilic (S N 2) attack of acetate ion on the dihaloalkane.
62 citations
TL;DR: In this paper, a Reihe elektroanalytischer methoden ermoglicht Aussagen uber den Mechanismus der Elektrodenreaktion, wahrend die Herstellung gespannter Kleinringe oder the reduktive Addition of Halogeniden an Carbonylverbindungen uber intermediare Carbanionen gelingt.
Abstract: Durch Elektrolyse last sich die Reaktivitat eines Substrates andern oder sogar umpolen („Redox-Umpolung”). Damit werden das Kohlenstoffgerust und die funktionellen Gruppen eines Synthesebausteins okonomischer nutzbar, und zugleich lassen sich Reaktionsschritte in mehrstufigen Synthesen einsparen. Als Werkzeug fur die Elektrolyse werden die Zelle, die Stromquelle, die Elektroden und der Elektrolyt benotigt, wobei man Elektroden und Elektrolyt nach Kenntnis des Reduktions- oder Oxidationspotentials des Substrates auswahlt. Eine Reihe elektroanalytischer Methoden ermoglicht Aussagen uber den Mechanismus der Elektrodenreaktion. An der Anode dimerisieren Arene, Phenylether und elektronenreiche Olefine uber Radikalkationen als Zwischenstufe. Carbonsaure-Anionen decarboxylieren bei der Kolbe-Elektrolyse zu Radikalen, die kuppeln oder sich an Olefine addieren; die Kolbe-Elektrolyse eignet sich auch zur Synthese von Pheromonen. An der Kathode lassen sich aktivierte Olefine uber Radikalanionen hydrodimerisieren oder mit entsprechenden Reagentien acylieren, alkylieren und carboxylieren. Pinakole, gekreuzte Hydrodimere, cyclische und arylierte Verbindungen sind uber kathodisch erzeugte Radikale zuganglich, wahrend die Herstellung gespannter Kleinringe oder die reduktive Addition von Halogeniden an Carbonylverbindungen uber intermediare Carbanionen gelingt.
53 citations
TL;DR: In this article, the reduction of carbonyl groups with an anti-Prelog fashion to give (R)-alcohols was examined and the effect of the structure of substrate on the stereochemical course as well as the selectivity were discussed.
49 citations
TL;DR: The hydrogenation of RCOCH2COR over a Raney nickel catalyst modified with a mixture of tartaric acid and NaBr gave (R*, R*-RCH(OH)CH2CH(O)R selectively with a high optical purity as mentioned in this paper.
Abstract: The hydrogenation of RCOCH2COR over a Raney nickel catalyst modified with a mixture of tartaric acid and NaBr gave (R*, R*-RCH(OH)CH2CH(OH)R selectively with a high optical purity. The substrates with R=CH3–, CH3CH2–, CH3CH2CH2–, CH3(CH2)4CH2–, and Ph– were employed in this study. In all cases, the recrystallization of the hydrogenation product gave an optically pure (R*,R*)-isomer which was free from the (R*,S*)-isomer.
48 citations