Preferred overall syn-elimination in metal promoted cycloalkene formation from vicinal dibromides

Sicher, J.; Havel, M.; Svoboda, Martin

doi:10.1016/s0040-4039(00)76404-5

Cited by 9 publications

(7 citation statements)

References 12 publications

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“…Indeed, bulk Li [23] or Na [24] metal in THF are usually employed in large excess and for relatively long reaction times, whilst our reagents are employed in stoichiometric amounts (or in a slight excess), and drive reactions to completion within a very short reaction time, under mild conditions. Na naphthalenide [1m,25] is a particularly effective reagents towards aliphatic (or alicyclic) dihalides, but reduction of stilbene dibromides led to the formation of complex reaction mixtures.…”

Section: Discussionmentioning

confidence: 99%

A new and highly effective organometallic approach to 1,2-dehalogenations and related reactions

Azzena

Pittalis

Dettori

et al. 2007

Journal of Organometallic Chemistry

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Section: Discussionmentioning

confidence: 99%

A new and highly effective organometallic approach to 1,2-dehalogenations and related reactions

Azzena

Pittalis

Dettori

et al. 2007

Journal of Organometallic Chemistry

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“…Some of the reactivity parameters are listed in Table 2. 18 Reductions promoted by Cr(II). Cr(II) was used as a model reducing agent because it has been 19 demonstrated to act as a one-electron reductant of vicinal dibromides, at least in mixed 20 dimethylsulfoxide/water solution (20)(21)(22)32). For both the DBPs and (±)-SBr 2 , the rate of 21 reduction by Cr(II) was fast relative to hydrolysis, and disappearance exhibited pseudo-first order 22 kinetics.…”

mentioning

confidence: 99%

“…10 Reductions promoted by iodide. The stereospecificity encountered in reduction of the dibromide 11 probe molecules by iodide was explored because prior work has shown that this species serves as 12 a nucleophilic (two-electron) "X-philic" reductant, at least in organic solvents (20)(21)(22)32).…”

mentioning

confidence: 99%

Alkyl Bromides as Mechanistic Probes of Reductive Dehalogenation: Reactions of Vicinal Dibromide Stereoisomers with Zerovalent Metals

Totten

Jans

Roberts

2001

Environ. Sci. Technol.

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Whether reductive dehalogenation proceeds via a one-or a two-electron mechanism has been suggested to affect product distributions, hence potentially influencing the success of engineered treatment systems. In this work, we explore vicinal dibromide stereoisomers as "probes" of the concertedness of electron transfer in reduction by aqueous suspensions of iron and zinc metal. Dibromides consisted of 2,3-dibromopentane (diBP) stereoisomers and (()-1,2-dibromo-1,2-diphenylethane. All dibromides reacted with metals to give the same E:Z ratio of olefins observed during dehalogenation by iodide (a two-electron reductant). Reduction by Cr(II) (a one-electron reductant) yielded distinctly different proportions of E and Z olefins. Although this might be construed as evidence that metals function as two-electron reductants, high stereospecificity was also obtained for reduction of diBPs by Fe(II) adsorbed to goethite, a presumed one-electron reductant; this can be explained by two single-electron transfers in rapid succession, facilitated by the locally elevated concentration of reducing equivalents at the oxide-water interface. The results suggest that reduction of alkyl halides by metals is not likely to produce free radicals that persist long enough to undergo radical-radical coupling or hydrogen-atom abstraction from minor dissolved constituents. Apparent free-radical coupling products are more likely to result from (possibly surface-bound) organometallic intermediates.

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“…Previous studies have shown that the debromination of vicinal dibromides by metals such as magnesium and zinc involves exclusively trans elimination of bromine. [19][20][21][22][23][24][25][26] Therefore, a sample of TBCD-5 was dissolved in hot ethanol and added to one equivalent of zinc powder. The mixture was allowed to cool and stirred for two days.…”

Section: Debromination Of Tbcd-5 For Synthesis Of Dbcd-9mentioning

confidence: 99%

“…66 : 34 (TBCD-6 : TBCD-7). The solid (5.82 g) was then repeatedly recrystallised from acetonitrile until the solid obtained was pure TBCD-6 ( Br 2 ), <1%), 403 (M + − 79 Br, 3.5), 401 (M + − 81 Br, 3.5), 321 (M + − H − 79 Br − 81 Br, 5), 241 (10), 239 (10), 160 (12), 159 (49), 131 (15), 119 (20), 105 (25)…”

Section: Tbcd-7 By Bromination Of Cdtmentioning

confidence: 99%

An extensive study of bromination of cis,trans,trans-1,5,9-cyclododecatriene: product structures and conformations

et al. 2005

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Bromine has been added to cis,trans,trans-1,5,9-cyclododecatriene under various reaction conditions. All expected direct addition products have been isolated, and their structures have been determined by microanalysis, NMR and X-ray crystallography. Advanced NMR techniques were used to determine solution conformations of several of the compounds, enabling comparison with the solid-state conformations obtained by crystallography.

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Preferred overall syn-elimination in metal promoted cycloalkene formation from vicinal dibromides

Cited by 9 publications

References 12 publications

A new and highly effective organometallic approach to 1,2-dehalogenations and related reactions

A new and highly effective organometallic approach to 1,2-dehalogenations and related reactions

Alkyl Bromides as Mechanistic Probes of Reductive Dehalogenation: Reactions of Vicinal Dibromide Stereoisomers with Zerovalent Metals

An extensive study of bromination of cis,trans,trans-1,5,9-cyclododecatriene: product structures and conformations

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