Addition of Bromine to Ketenes and Bisketenes

Electrophilic Attack at Carbonyl Carbon and Neighboring Group Participation

R. S. Brown, Manfred Christi, Alan J. Lough, Jihai Ma, Eva Maria Peters, Karl Peters, Frank Sammtleben, Henryka Slebocka-Tilk, Kuang-Sen Sung, Thomas T. Tidwell

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Addition of bromine to bisketene (Me3SiC=C=O)2 (1) gave the fumaryl dibromide E-7, whose stereochemistry was proven by X-ray structure determination. Upon warming, E-7 rearranged to the furanone 8, and this process was faster in the more polar CD3CN compared to CDCl3, consistent with an ionization pathway for the rearrangement. The bromination of 1 in CH2ClCH2Cl followed second-order kinetics with a rate constant (2.1 ± 0.1) × 104 M-1 s-1 at 25°C. The first-order dependence of bromine addition to 1 on [Br2] is attributed to intramolecular nucleophilic assistance by the second ketenyl moiety in an initial complex of 1 and Br2 to give E-7. A transition structure for this process has been calculated by ab initio methods. By contrast PhMe2SiCH=C=O 11 and γ-oxoketene 16 underwent bromination by third-order kinetics, second order in [Br2], indicating the absence of neighboring group participation in the rate-limiting step. The bisketene Me2Si-(CH=C=O)2 (13) underwent bromination by mixed kinetics with both first- and second-order terms in [Br2].

Original languageEnglish
Pages (from-to)6000-6006
Number of pages7
JournalJournal of Organic Chemistry
Volume63
Issue number17
DOIs
Publication statusPublished - 1998 Aug 21

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Bromine
Carbon
Kinetics
Stereochemistry
Ionization
Rate constants
X rays

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

Cite this

Brown, R. S., Christi, M., Lough, A. J., Ma, J., Peters, E. M., Peters, K., ... Tidwell, T. T. (1998). Addition of Bromine to Ketenes and Bisketenes: Electrophilic Attack at Carbonyl Carbon and Neighboring Group Participation. Journal of Organic Chemistry, 63(17), 6000-6006. https://doi.org/10.1021/jo980684h
Brown, R. S. ; Christi, Manfred ; Lough, Alan J. ; Ma, Jihai ; Peters, Eva Maria ; Peters, Karl ; Sammtleben, Frank ; Slebocka-Tilk, Henryka ; Sung, Kuang-Sen ; Tidwell, Thomas T. / Addition of Bromine to Ketenes and Bisketenes : Electrophilic Attack at Carbonyl Carbon and Neighboring Group Participation. In: Journal of Organic Chemistry. 1998 ; Vol. 63, No. 17. pp. 6000-6006.
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abstract = "Addition of bromine to bisketene (Me3SiC=C=O)2 (1) gave the fumaryl dibromide E-7, whose stereochemistry was proven by X-ray structure determination. Upon warming, E-7 rearranged to the furanone 8, and this process was faster in the more polar CD3CN compared to CDCl3, consistent with an ionization pathway for the rearrangement. The bromination of 1 in CH2ClCH2Cl followed second-order kinetics with a rate constant (2.1 ± 0.1) × 104 M-1 s-1 at 25°C. The first-order dependence of bromine addition to 1 on [Br2] is attributed to intramolecular nucleophilic assistance by the second ketenyl moiety in an initial complex of 1 and Br2 to give E-7. A transition structure for this process has been calculated by ab initio methods. By contrast PhMe2SiCH=C=O 11 and γ-oxoketene 16 underwent bromination by third-order kinetics, second order in [Br2], indicating the absence of neighboring group participation in the rate-limiting step. The bisketene Me2Si-(CH=C=O)2 (13) underwent bromination by mixed kinetics with both first- and second-order terms in [Br2].",
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Brown, RS, Christi, M, Lough, AJ, Ma, J, Peters, EM, Peters, K, Sammtleben, F, Slebocka-Tilk, H, Sung, K-S & Tidwell, TT 1998, 'Addition of Bromine to Ketenes and Bisketenes: Electrophilic Attack at Carbonyl Carbon and Neighboring Group Participation', Journal of Organic Chemistry, vol. 63, no. 17, pp. 6000-6006. https://doi.org/10.1021/jo980684h

Addition of Bromine to Ketenes and Bisketenes : Electrophilic Attack at Carbonyl Carbon and Neighboring Group Participation. / Brown, R. S.; Christi, Manfred; Lough, Alan J.; Ma, Jihai; Peters, Eva Maria; Peters, Karl; Sammtleben, Frank; Slebocka-Tilk, Henryka; Sung, Kuang-Sen; Tidwell, Thomas T.

In: Journal of Organic Chemistry, Vol. 63, No. 17, 21.08.1998, p. 6000-6006.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Addition of Bromine to Ketenes and Bisketenes

T2 - Electrophilic Attack at Carbonyl Carbon and Neighboring Group Participation

AU - Brown, R. S.

AU - Christi, Manfred

AU - Lough, Alan J.

AU - Ma, Jihai

AU - Peters, Eva Maria

AU - Peters, Karl

AU - Sammtleben, Frank

AU - Slebocka-Tilk, Henryka

AU - Sung, Kuang-Sen

AU - Tidwell, Thomas T.

PY - 1998/8/21

Y1 - 1998/8/21

N2 - Addition of bromine to bisketene (Me3SiC=C=O)2 (1) gave the fumaryl dibromide E-7, whose stereochemistry was proven by X-ray structure determination. Upon warming, E-7 rearranged to the furanone 8, and this process was faster in the more polar CD3CN compared to CDCl3, consistent with an ionization pathway for the rearrangement. The bromination of 1 in CH2ClCH2Cl followed second-order kinetics with a rate constant (2.1 ± 0.1) × 104 M-1 s-1 at 25°C. The first-order dependence of bromine addition to 1 on [Br2] is attributed to intramolecular nucleophilic assistance by the second ketenyl moiety in an initial complex of 1 and Br2 to give E-7. A transition structure for this process has been calculated by ab initio methods. By contrast PhMe2SiCH=C=O 11 and γ-oxoketene 16 underwent bromination by third-order kinetics, second order in [Br2], indicating the absence of neighboring group participation in the rate-limiting step. The bisketene Me2Si-(CH=C=O)2 (13) underwent bromination by mixed kinetics with both first- and second-order terms in [Br2].

AB - Addition of bromine to bisketene (Me3SiC=C=O)2 (1) gave the fumaryl dibromide E-7, whose stereochemistry was proven by X-ray structure determination. Upon warming, E-7 rearranged to the furanone 8, and this process was faster in the more polar CD3CN compared to CDCl3, consistent with an ionization pathway for the rearrangement. The bromination of 1 in CH2ClCH2Cl followed second-order kinetics with a rate constant (2.1 ± 0.1) × 104 M-1 s-1 at 25°C. The first-order dependence of bromine addition to 1 on [Br2] is attributed to intramolecular nucleophilic assistance by the second ketenyl moiety in an initial complex of 1 and Br2 to give E-7. A transition structure for this process has been calculated by ab initio methods. By contrast PhMe2SiCH=C=O 11 and γ-oxoketene 16 underwent bromination by third-order kinetics, second order in [Br2], indicating the absence of neighboring group participation in the rate-limiting step. The bisketene Me2Si-(CH=C=O)2 (13) underwent bromination by mixed kinetics with both first- and second-order terms in [Br2].

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