Английская Википедия:Catecholborane
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.
Synthesis and structure
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 described the reaction of alkali-metal boron hydride (LiBH4, NaBH4, KBH4) with tris(catecholato)bisborane in an ethereal solvent such as diethyl ether.[1] In 2001, Herbert Brown and coworkers prepared catecholborane by treatment of tri-o-phenylene bis-borate with diborane.[2]
Unlike borane itself or alkylboranes, catechol borane exists as a monomer. This behavior is a consequence of the electronic influence of the aryloxy groups that diminish the Lewis acidity of the boron centre. Pinacolborane adopts a similar structure.
Reactions
Catecholborane is less reactive in hydroborations than borane-THF or borane-dimethylsulfide.
When catecholborane is treated with a terminal alkyne, a trans vinylborane is formed:
- C6H4O2BH + HC2R → C6H4O2B-CHCHR
The product is a precursor to the Suzuki reaction and is the only borane which stops at the alkene instead of reacting further to the alkane. [3][4]
Catecholborane may be used as a stereoselective reducing agent when converting β-hydroxy ketones to syn 1,3-diols.
Catecholborane oxidatively adds to low valent metal complexes, affording boryl complexes.[5]
- C6H4O2BH + Pt(PR3)2 → (C6H4O2B)Pt(PR3)2H
References
- ↑ Process for producing catecholborane – Patent 4739096
- ↑ Шаблон:Cite journal
- ↑ Janice Gorzynski Smith, Organic Chemistry: Second Ed. 2008. pp 1007
- ↑ Шаблон:OrgSynth
- ↑ Шаблон:Cite journal
