期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 23, 期 66, 页码 16853-16861出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201703609
关键词
catalysis; dehydrocoupling; hydroboration; lithium; main group
资金
- George Fraser scholarship
- EPSRC [EP/L027313/1]
- Royal Society of Edinburgh (BP Trust)
- University of Strathclyde
- Engineering and Physical Sciences Research Council [1489071, EP/L027313/1] Funding Source: researchfish
- EPSRC [EP/L027313/1] Funding Source: UKRI
Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1-lithium-2-tert-butyl-1,2-dihydropyridine (1tLi) functions as a precatalyst to convert Me2NH center dot BH3 to [NMe2BH2](2) (89% conversion) under competitive conditions (2.5 mol%, 60 h, 80 degrees C, toluene solvent) to that of previously reported LiN(SiMe3)(2). Sodium and potassium dihydropyridine congeners produce similar high yields of [NMe2BH2](2) but require longer times. Switching the solvent to pyridine induces a remarkable change in the dehy-drocoupling product ratio, with (NMe2)(2)BH favoured over [NMe2BH2](2) (e.g., 94%: 2% for 1tLi). Demonstrating its versatility, precatalyst 1tLi was also successful in promoting hydroboration reactions between pinacolborane and a selection of aldehydes and ketones. Most reactions gave near quantitative conversion to the hydroborated products in 15 minutes, though sterically demanding carbonyl substrates require longer times. The mechanisms of these rare examples of Group 1 metal-catalysed processes are discussed.
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