Stereochemistry of polar 1,4-addition of bromine to dienes. Structure assignments for dibromocyclohexenes and dibromohexenes

Heasley, Gene E.; Heasley, Victor L.; Manatt, Stanley L.; Day, Howard A.; Hodges, Ronald V.; Kroon, Paulus A.; Redfield, David; Rold, Tracy L.; Williamson, D. E.

doi:10.1021/jo00963a004

Cited by 36 publications

(14 citation statements)

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“…The reported kinetic yields 9 are given in Table and were essentially the same in CCl 4 as in CH 2 Cl 2 solvent. The relative thermodynamic yields reported for these isomers in CCl 4 also are given in Table and are virtually the same at 78 °C as at 25 °C …”

Section: Resultsmentioning

confidence: 74%

“…Although the relative yields of 5 were reported not to depend on whether the solvent was CH 2 Cl 2 or CCl 4 , the yields do depend on temperature . At −70 °C, the major product is 5a , whereas at room temperature the product is almost entirely 5b .…”

Section: Resultsmentioning

confidence: 96%

“…Initial protection of the double bonds is helpful, as the diol readily dehydrates to phenol. Bromination , is one method of protecting the double bonds of alkenes. , However, reports of electrophilic bromination of 1 have led to conflicting results concerning the products formed. − Therefore, we have investigated the bromination of 1 and 2 in order to determine the usefulness of this reaction in protecting the double bonds of these dienes.…”

Section: Introductionmentioning

confidence: 99%

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Bromination of Cyclohexa-1,3-diene and (R,S)-Cyclohexa-3,5-diene-1,2-diol

et al. 1999

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The configuration of 1,2,3,4-tetrabromocyclohexane (mp 90 °C), 5a, has been established as 1,2t,3t,4c by an X-ray crystallographic determination. The structures of two of three dibromocyclohexenes (3a, 3b, and 3c) have been reassigned on the basis of NMR evidence and an X-ray crystallographic determination of the structure of 3b (trans-3,6-dibromocyclohexene). The structures of the two major isomers of 3,4,5,6-tetrabromocyclohexane-1,2-diol obtained by bromination of cis-cyclohexa-3,5-diene-1,2-diol also were established by X-ray crystallographic determinations of their monobenzoate esters. Studies of their formation indicate that the mechanism of bromination of 1,3-cyclohexadiene and cis-cyclohexa-3,5-diene-1,2-diol are similar. Addition of 1 equiv of bromine occurs rapidly by anti 1,2-addition, which is followed by rearrangements to form products of conjugation addition. A second equivalent of bromine adds to afford mostly the 1,2t,3t,4c-tetrabromo compounds at −70 °C and, with cyclohexadiene, the 1,2t,3c,4t-tetrabromo compound at higher temperature.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Bromination of Cyclohexa-1,3-diene and (R,S)-Cyclohexa-3,5-diene-1,2-diol

et al. 1999

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“…Whereas an isomer of 11 , hexa-2,5-diene, behaves similarly to 11 [ 9 ], the terminally fully methylated diene 14 does not react further than 15 on bromine addition, no tetrabromide 16 being formed [ 10 ].…”

Section: Resultsmentioning

confidence: 99%

The chemical behavior of terminally tert-butylated polyolefins

Klein¹,

Hopf²,

Jones³

et al. 2015

Beilstein J. Org. Chem.

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SummaryThe chemical behavior of various oligoenes 2 has been studied. The catalytic hydrogenation of diene 3 yielded monoene 4. Triene 7 was hydrogenated to diene 8, monoene 9 and saturated hydrocarbon 10. Bromine addition to 3 and 7 yielded the dibromides 17 and 18, respectively, i.e., the oligoene system has been attacked at its terminal olefinic carbon atoms. Analogously, the higher vinylogs 19 and 20 yielded the 1,8- and 1,10-bromine adduts 23 and 24, respectively, when less than 1 equivalent of bromine was employed. Treatment of tetraene 19 with excess bromine provided tetrabromide 25. In epoxidation reactions, both with meta-chloroperbenzoic acid (MCPBA) and dimethyldioxirane (DMDO) two model oligoenes were studied: triene 7 and tetraene 19. Whereas 7 furnished the rearrangement product 31 with MCPBA, it yielded the symmetrical epoxide 32 with DMDO. Analogously, 19 was converted to mono-epoxide 33 with MCPBA and to 34 with DMDO. Diels–Alder addition of 7 with N-phenyltriazolinedione (PTAD) did not take place. Extension of the conjugated π-system to the next higher vinylog, 19, caused NPTD-addition to the symmetrical adduct 37 in good yield. Comparable results were observed on adding NPTD (equivalent amount) to pentaene 20 and hexaene 21. Using 36 in excess provided the 2:1-adduct 40 from 21 and led to a complex mixture of adducts from heptaene 22. With tetracyanoethylene (TCNE) as the dienophile, tetraolefin 19 yielded the symmetrical adduct 43, although the reaction temperature had to be increased. Pentaene 20 and hexaene 21 led to corresponding results, adducts 44 and 45 being produced in acceptable yields. With nonaene 42 and TCNE the 2:1-adduct 48 was generated according to its spectroscopic data. Exploratory photochemical studies were carried out with tetraene 19 as the model compound. On irradiation this reacted with oxygen to the stable endo-peroxide 52.

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“…This is consistent with the stereochemical outcome (syn) of the overall addition of Br 2 across a 1,3-diene where the participating orbital array is essentially identical. 19 The above findings represent fundamental stereochemical information with respect to electrophilic 1,4-addition across an enyne. Moreover, it should guide the choice of enyne geometry required in the synthesis of natural products from Laurencia species.…”

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confidence: 78%