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 language | English |
|---|---|
| Pages (from-to) | 6000-6006 |
| Number of pages | 7 |
| Journal | Journal of Organic Chemistry |
| Volume | 63 |
| Issue number | 17 |
| DOIs | |
| Publication status | Published - 1998 Aug 21 |
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All Science Journal Classification (ASJC) codes
- Organic Chemistry
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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 journal › Article
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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U2 - 10.1021/jo980684h
DO - 10.1021/jo980684h
M3 - Article
VL - 63
SP - 6000
EP - 6006
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
SN - 0022-3263
IS - 17
ER -