| Catecholborane | |
|---|---|
|
Catecholborane |
|
|
Other names
1,3,2-benzodioxaborole |
|
| Identifiers | |
| CAS number | 274-07-7 |
| ChemSpider | 10617125 |
| Jmol-3D images | Image 1 Image 2 |
|
|
|
|
| Properties | |
| Molecular formula | C6H5BO2 |
| Molar mass | 119.92 g/mol |
| Appearance | Colorless liquid |
| Density | 1.125 g/cm³, liquid |
| Melting point |
12 °C |
| Boiling point |
50 °C/50 mmHg |
| Hazards | |
| R-phrases | R11, R14, R34 |
| S-phrases | S16, S26, S36/37/39, S43, S45 |
| NFPA 704 |
4
1
2
|
| Flash point | 2 °C |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
|
| Infobox references | |
Catecholborane (abbreviated HBcat) is an organoboron compound that is useful in organic synthesis. This colourless liquid is a derivative of catechol and a borane, having the formula C6H4O2BH.
Contents |
Traditionally catecholborane is produced by treating catechol with borane (BH3) in a cooled solution of THF. However, this method results in a loss of 2 mole equivalents of the hydride. Nöth and Männig devised a more economical method involves the reaction of alkali-metal boron hydride (LiBH4, NaBH4, of KBH4) with tris(catecholato)bisborane in an ethereal solvent such as diethyl ether.[1] In 2001 Herbert Brown released an additional procedure for catecholborane synthesis. His method involves treating tri-O-phenylene bis-borate with diborane in a solution of either triglyme or tetraglyme. Brown claimed his method produces 85% yield of 97% pure product, catecholborane.[2]
Unlike borane itself or alkylboranes, catechol borane exists as a monomer. This behavior is a consequence of the electronic influence of the alkoxy groups that diminish the Lewis acidity of the boron centre. Pinacolborane adopts a similar structure.
Catechol borane is less reactive than borane itself.
When catecholborane is treated with an alkyne, usually a terminal alkyne, through hydroboration a trans vinylborane is formed. The product is a precursor to the Suzuki reaction.[3]
Catecholborane may be used as a stereoselective reducing agent when converting β-hydroxy ketones to syn 1,3-diols.[5]