Molecular addition compounds.  4.  Unusually slow reaction of tertiary amines with 9-borabicyclo[3.3.1]nonane (9-BBN) dimer.  New, stable, mildly reactive amine complexes of 9-BBN

Brown, Herbert C.; Kulkarni, Surendra U.

doi:10.1021/ic50178a020

Cited by 20 publications

(3 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, only 1 equiv of SMe 2 was required for the preparation of IpcBHCl·SMe 2 (>98%) in EE and CH 2 Cl 2 . As a result, the rate of hydroboration of 2-methyl-2-butene was relatively faster with IpcBHCl· SMe 2 (not containing excess CS) than with IpcBHCl·THF (containing excess CS) in EE and CH 2 Cl 2 . , Thus, at 0 °C, more than 50% hydroboration with IpcBHCl·SMe 2 was complete in less than 30 min, while 4 and 6 h were required to complete the reaction in EE and CH 2 Cl 2 , respectively. These results are graphically represented in Figure .…”

Section: Resultsmentioning

confidence: 96%

“…The hydroboration of 2-methyl-2-butene with IpcBH 2 in THF was faster than that observed in EE, pentane, and CH 2 Cl 2 . This may be explained by the fact that IpcBH 2 ·THF, a reactive monomeric species, undergoes a relatively fast dissociation into IpcBH 2 , which reacts relatively rapidly with alkene, resulting in further dissociation of the IpcBH 2 −dimer to the reactive IpcBH 2 · THF complex, readily available for hydroboration …”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Hydroboration. 92. Investigation of Practical Methods for the Synthesis of Optically Pure Isopinocampheylchloroborane for the Asymmetric Hydroboration of Representative Prochiral Alkenes

1996

Self Cite

View full text Add to dashboard Cite

A quantitative study was made of the preparation of the optically pure borane reagent, isopinocampheylchloroborane (IpcBHCl), potentially valuable for asymmetric hydroboration. IpcBHCl (87−90%) in equilibrium with 5−6.5% of IpcBCl2 and IpcBH2, respectively, can be prepared conveniently by a number of relatively simple operations: (1) the reaction of isopinocampheylborane (IpcBH2) with anhydrous hydrochloric acid (HCl) in ethyl ether (EE); (2) the reaction of stoichiometric amounts of IpcBH2 with isopinocampheyldichloroborane (IpcBCl2) in EE; and (3) the reduction of IpcBCl2 with trimethylsilane (Me3SiH) or lithium aluminum hydride (LAH) in EE. The reduction of IpcBCl2 with Me3SiH in pentane proceeds extremely slowly to provide the desired reagent, IpcBHCl. However, in EE, the reduction proceeds much faster, providing an equilibrium mixture of 90% IpcBHCl, 5% IpcBH2, and 5% IpcBCl2. We also investigated the reduction of IpcBCl2 with Me3SiH in pentane and dichloromethane (CH2Cl2) in the presence of known amounts of EE, tetrahydrofuran (THF), and dimethyl sulfide (SMe2), solvents which coordinate with the dichloroboranes. A comparative study of the rate of hydroboration of the alkene, 2-methyl-2-butene, with IpcBH2 and IpcBHCl, obtained as described above, was made in representative solvents, such as pentane, CH2Cl2, EE, and THF, at 0 °C and, in many cases, also at 25 °C. This study revealed that the rate of hydroboration is faster in THF for IpcBH2, while for IpcBHCl, the rate is faster in EE. Asymmetric hydroboration of prochiral alkenes was achieved by two methods, viz., IpcBHCl, produced by the reaction of IpcBH2 with HCl in EE (method A), and the reduction−hydroboration reaction of IpcBCl2 with LAH (0.25 equiv) in the presence of the prochiral alkene (method B) in EE. In both methods, the temperature of the reaction mixture was maintained at −25 °C. Almost identical results were realized in these two procedures, with the enantiomeric excess (ee) realized with IpcBHCl, in some cases, considerably better than that achieved with IpcBH2. Although, IpcBHCl was obtained in only 87−90% purity along with IpcBH2 and IpcBCl2 as side products, the presence of the latter compound had no observable effect on the chiral outcome of the asymmetric hydroboration.

show abstract

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Hydroboration. 92. Investigation of Practical Methods for the Synthesis of Optically Pure Isopinocampheylchloroborane for the Asymmetric Hydroboration of Representative Prochiral Alkenes

1996

Self Cite

View full text Add to dashboard Cite

show abstract

“…The slow formation of AuNPs in the presence of higher concentrations of ODT has provided us the opportunity to investigate the reducing character of 9-BBN, including the role of complex formation with alkylthiolates and the potential impact on hydride formation. Previously, Brown and co-workers have shown that thiol-terminated primary or secondary alkyl hydrocarbons form complexes with hydroborating agents and rapidly liberate hydrogen gas. , In the case of 9-BBN, the reaction is shown in Scheme .…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic and Microscopic Investigation of Gold Nanoparticle Formation: Ligand and Temperature Effects on Rate and Particle Size

Sardar

Shumaker‐Parry

2011

J. Am. Chem. Soc.

View full text Add to dashboard Cite

We report a spectroscopic and microscopic investigation of the synthesis of gold nanoparticles (AuNPs) with average sizes of less than 5 nm. The slow reduction and AuNP formation processes that occur by using 9-borabicyclo[3.3.1]nonane (9-BBN) as a reducing agent enabled a time-dependent investigation based on standard UV-vis spectroscopy and transmission electron microscopy (TEM) analyses. This is in contrast to other borohydride-based syntheses of thiolate monolayer protected AuNPs which form particles very rapidly. We investigated the formation of 1-octadecanethiol (ODT) protected AuNPs with average diameters of 1.5-4.3 nm. By studying the progression of nanoparticle formation over time, we find that the nucleation rate and the growth time, which are interlinked with the amount of ODT and the temperature, influence the size and the size dispersion of the AuNPs. High-resolution TEM (HRTEM) analyses also suggest that the nanoparticles are highly single crystalline throughout the synthesis and appear to be formed by a diffusion-controlled Ostwald-ripening growth mechanism.

show abstract

9-Borabicyclo[3.3.1]nonane Dimer

Soderquist

Roush²,

Heo³

2004

Encyclopedia of Reagents for Organic Synthesis

View full text Add to dashboard Cite

Molecular addition compounds. 4. Unusually slow reaction of tertiary amines with 9-borabicyclo[3.3.1]nonane (9-BBN) dimer. New, stable, mildly reactive amine complexes of 9-BBN

Cited by 20 publications

References 9 publications

Hydroboration. 92. Investigation of Practical Methods for the Synthesis of Optically Pure Isopinocampheylchloroborane for the Asymmetric Hydroboration of Representative Prochiral Alkenes

Hydroboration. 92. Investigation of Practical Methods for the Synthesis of Optically Pure Isopinocampheylchloroborane for the Asymmetric Hydroboration of Representative Prochiral Alkenes

Spectroscopic and Microscopic Investigation of Gold Nanoparticle Formation: Ligand and Temperature Effects on Rate and Particle Size

9-Borabicyclo[3.3.1]nonane Dimer

Contact Info

Product

Resources

About