Electrophilic Halogenation of nido-5,6-C2B8H12

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Title:Electrophilic Halogenation of nido-5,6-C2B8H12
Creators:
Holub, Josef
Bakardjiev, Mario
Štíbr, Bohumil
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 71, 11-12, pp. 1549-1556
Uncontrolled Keywords:Halogenations, Boranes, Dicarbaboranes, Carboranes, Electrophilic substitutions, NMR spectroscopy

Abstract

Room-temperature chlorination of the dicarbaborane <i>nido</i>-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>12</sub> (<strong>1</strong>) with CCl<sub>4</sub> in the presence of anhydrous AlCl<sub>3</sub> yielded a mixture of 7-Cl-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>11</sub> (7-Cl-<strong>1</strong>) (yield 34%), 4-Cl-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>11</sub> (4-Cl-<strong>1</strong>) (yield 20%), 3-Cl-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>11</sub> (3-Cl-<strong>1</strong>) (yield 21%), and 3,4-Cl<sub>2</sub>-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>10</sub> (3,4-Cl<sub>2</sub>-<strong>1</strong>) (yield 26%), while a trisubstituted derivative, 3,4,7-Cl<sub>3</sub>-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>9</sub> (3,4,7-Cl<sub>3</sub>-<strong>1</strong>) (yield 80%), was isolated as a sole product at reflux. Bromination of compound <strong>1</strong> with elemental Br<sub>2</sub> in the presence of Al powder at ambient temperature in CS<sub>2</sub> gave a mixture of 7-Br-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>11</sub> (7-Br-<strong>1</strong>) (yield 31%) and 4,7-Br<sub>2</sub>-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>10</sub> (4,7-Br<sub>2</sub>-<strong>1</strong>) (yield 52%). The most selective was AlCl<sub>3</sub>-catalyzed iodination of <strong>1</strong> in refluxing benzene, which resulted in the formation of 7-I-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>11</sub> (7-I-<strong>1</strong>) (yield 85%). Although performed under different conditions, the experiments point to the following order of reactivity of individual positions in <strong>1</strong> in electrophilic halogenation: 7 &gt; 4 &gt; 3. Individual compounds were isolated and purified by liquid chromatography and characterized by mass spectrometry and NMR spectroscopy (<sup>11</sup>B, <sup>1</sup>H) combined with two-dimensional [<sup>11</sup>B-<sup>11</sup>B]-COSY and <sup>1</sup>H-{<sup>11</sup>B(selective)} NMR techniques. Various NMR effects of halo-substitution are discussed for the series of monosubstituted 7-X-5,6-C<sub>2</sub>B<sub>8</sub>H<sub>11</sub> (7-X-<strong>1</strong>) compounds (X = Cl, Br, and I). <p>

Title:Electrophilic Halogenation of nido-5,6-C2B8H12
Creators:
Holub, Josef
Bakardjiev, Mario
Štíbr, Bohumil
Uncontrolled Keywords:Halogenations, Boranes, Dicarbaboranes, Carboranes, Electrophilic substitutions, NMR spectroscopy
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:71
Number:11-12
Page Range:pp. 1549-1556
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20061549UNSPECIFIED
ID Code:2561
Item Type:Article
Deposited On:06 Feb 2009 17:19
Last Modified:06 Feb 2009 16:19

Citation

Holub, Josef; Bakardjiev, Mario; Štíbr, Bohumil (2006) Electrophilic Halogenation of nido-5,6-C2B8H12. Collection of Czechoslovak Chemical Communications, 71 (11-12). pp. 1549-1556. ISSN 0010-0765

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