Carborane Formation Research Articles

High Yielding Preparation of Dicarba-closo-dodecaboranes Using a Silver(I) Mediated Dehydrogenative Alkyne-Insertion Reaction

The synthesis of 1,2-dicarba-closo-dodecaboranes (ortho-carboranes) is often low yielding which is a critical issue given the increasing use of boron clusters in material science and medicinal chemistry. To address this barrier, a series of Cu, Ag, and Au salts were screened to identify compounds that would enhance the yields of ortho-caboranes produced when treating alkynes with B10H12(CH3CN)2. Using a variety of functionalized ligands including mono- and polyfunctional internal and terminal alkynes, significant increases in yield were observed when AgNO3 was used in catalytic amounts. AgNO3 appears to prevent unwanted reduction/hydroboration of the alkyne prior to carborane formation, and the process is compatible with aryl, halo, hydroxy, nitrile, carbamate, and carbonyl functionalized alkynes.

Theoretical Study of the Reaction of Acetylene with B4H8. A Proposed Mechanism of Carborane Formation. 2

A uniform computational level ([MP4/6-311+G(d,p)]//MP2/6-31G(d)+ZPC) is used to evaluate 18 intermediates and 12 transition states in the study of the mechanism of carborane formation, beginning with the elimination of H2 from B4H10 and ending with the formation of 1,2-C2B4H6. The calculated activation barrier (33.0 kcal/mol) for the first step (B4H10 → B4H8 + H2) is higher than experiment (23.7 kcal/mol) but in agreement with higher-level theory (CBS-Q, 34.4 kcal/mol). The first stable intermediate is a −CHCH− bridged B4H8 species, which is structurally similar to the known −CH2−CH2− bridged B4H8 structure. The hydroboration pathway for insertion of C2H2 into a BH bond of B4H8 has a slightly lower activation barrier than the addition barrier of C2H2 to B4H8 (10.1 versus 13.1 kcal/mol, respectively). The hydroboration reaction leads, in a series of steps, to 2,5-μ-CH2-1-CB4H7, a known product in the reaction of methylacetylene and B4H10.

Theoretical Study of the Reaction of Acetylene with BH3, B2H6, and B3H7. A Proposed Mechanism of Carborane Formation

Theoretical Study of the Reaction of Acetylene with BH3, B2H6, and B3H7. A Proposed Mechanism of Carborane Formation

Tumour-targetted boranes. Part 2. Coupling of closo-carboranes to substituted 2-nitroimidazoles via 1,3-dipolar cycloaddition

Carboranes targetted to specific tumour tissues are important for boron neutron capture therapy of cancer. Direct syntheses of carboranes linked to 2-nitroimidazole were unsuccessful. A mild procedure for 1, 3-dipolar cycloaddition of 4-(carboranylmethoxy)benzonitrile N-oxide 32 with a nitroimidazolyl-alkene 27 and with nitroimidazolyl-alkynes 3 and 30 has been developed, using a series of model reactions, yielding a dihydroisoxazole 28 and the isoxazoles 29 and 31, respectively. The nitrite oxide 32 is unusually stable. Dithioacetals are shown to be suitable protecting groups for aromatic aldehydes under the vigorous reductive and Lewis acidic-basic conditions of carborane formation. 6- Methoxy-4H-[1] benzopyrano [4,3-c] isoxazole 16 has been synthesised by intramolecular 1,3-dipolar cycloaddition. The structure of the isoxazole derivative 29 has been confirmed by an X-ray crystal structure analysis.

Peralkylated 1,4-dibora-2,5-cyclohexadienes-formation and rearrangement into peralkylated nido-2,3,4,5- tetracarbahexaboranes(6)

Peralkylated 1,4-dibora-2,5-cyclohexadienes (DBCH) ( 3a,b) and a pentaalkylaryl derivative ( 3c) are formed in high yield at low temperature (−78 to −30°C) via the reaction between 1,5,7,11-tetramethyl-2,3,4,8,9,10- hexaisopropyl-3,9-dibora-6-stanna- 1,4,7,10-spiro[5.5]undekatetraene ( 8) and organoboron (dihalides (MeBBr 2, 1PrBBr 2, PhBCl 2). In contrast with claims in the literature for stable peralkylated DBCH derivatives, compounds 3 rearrange between −30 and +25°C into the nido-2,3,4,5-tetra- carbahexaboranes(6) ( 5). The specific arrangement of the substituents in the 2,3,4,5-position (Me, 1Pr, Me, 1Pr) is noteworthy. This indicates, together with the formation of carboranes (e.g. 5a from 3a) in which substituents at the boron atoms must have been exchanged, that cleavage of the DBCH derivatives ( 3) into borirenes ( 1) is involved at least to some extent. Attempts to prepare a borirene (1-methyl-2,3-ditert-butyl-borirene, 1a) by the reported reaction between the system C 8K/MeBBr 2 and ditert- butylethyne have failed. All reactions were monitored by 1H, 11B, 13C, and 119Sn NMR spectroscopy and the same methods served for the final structural assigmnent of the DBCH derivatives 3 and the carbaboranes 5.

Kinetics and mechanism of carborane formation

Kinetics and mechanism of carborane formation

Carborane formation in alkyne-borane gas-phase systems. V. Conversion of two-carbon to four-carbon carboranes via alkyne insertion. Nuclear magnetic resonance studies of tetracarba-nido-hexaboranes

Carborane formation in alkyne-borane gas-phase systems. V. Conversion of two-carbon to four-carbon carboranes via alkyne insertion. Nuclear magnetic resonance studies of tetracarba-nido-hexaboranes

Formation of carboranes by pyrolysis of trimethylborane

Pyrolysis of trimethylborane at 475–520 °C yields Me2BCH2BMe2 and the carboranes C2H2(BMe)3 and C4H4(BMe)6; mass spectral evidence suggests also the formation of (MeBCH2)3 and (MeBCH2)4 and other less-volatile carboranes.

Carborane formation in alkyne-borane gas-phase systems. IV. Mechanism study of the tetraborane(10)-acetylene reaction

Carborane formation in alkyne-borane gas-phase systems. IV. Mechanism study of the tetraborane(10)-acetylene reaction

Carborane formation in alkyne-borane gas phase systems. III. Flash reactions of small boranes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarborane formation in alkyne-borane gas phase systems. III. Flash reactions of small boranesRussell N. Grimes, Christopher L. Bramlett, and R. Leonard VanceCite this: Inorg. Chem. 1969, 8, 1, 55–58Publication Date (Print):January 1, 1969Publication History Published online1 May 2002Published inissue 1 January 1969https://doi.org/10.1021/ic50071a013RIGHTS & PERMISSIONSArticle Views68Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (493 KB) Get e-Alerts Get e-Alerts

Monocarbon carboranes II. Syntheses of carborane derivatives by reaction of group IV halides with cyanoboron hydrides

Reaction of the B 10H 13CN 2− ion with alkyl iodides in tetrahydrofuran/water produces a mixture of B 10H 12CN(H) n R 3- n carboranes. The unsubstituted molecule, B 10H 12CNH 3 is obtained by treatment of B 10H 13CN 2− with either trimethylsilyl or trimethyltin chloride followed by base hydrolysis. Methylation of B 10H 12CN[S-(CH 3) 2 − in tetrahydrofuran/methanol gives a single isomer of the composition B 10H 11(OCH 3)CN(CH 3) 3. Observations which suggest that carborane formation may proceed thru a B 10H 13CNR − intermediate are presented.

Carborane formation in alkyne-borane gas-phase systems. II. Slow reactions of tetraborane(10) and pentaborane(11) with acetylene, methylacetylene, and dimethylacetylene

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarborane formation in alkyne-borane gas-phase systems. II. Slow reactions of tetraborane(10) and pentaborane(11) with acetylene, methylacetylene, and dimethylacetyleneRussell Grimes N., Christopher L. Bramlett, and R. Leonard VanceCite this: Inorg. Chem. 1968, 7, 6, 1066–1070Publication Date (Print):June 1, 1968Publication History Published online1 May 2002Published inissue 1 June 1968https://doi.org/10.1021/ic50064a005RIGHTS & PERMISSIONSArticle Views59Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (656 KB) Get e-Alerts Get e-Alerts