1-Alkali-metal-2-alkyl-1,2-dihydropyridines: Soluble Hydride Surrogates for Catalytic Dehydrogenative Coupling and Hydroboration Applications.
Chemistry
; 23(66): 16853-16861, 2017 Nov 27.
Article
in En
| MEDLINE
| ID: mdl-28940713
ABSTRACT
Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1-lithium-2-tert-butyl-1,2-dihydropyridine (1tLi) functions as a precatalyst to convert Me2 NHâ
BH3 to [NMe2 BH2 ]2 (89 % conversion) under competitive conditions (2.5â
mol %, 60â
h, 80 °C, toluene solvent) to that of previously reported LiN(SiMe3 )2 . Sodium and potassium dihydropyridine congeners produce similar high yields of [NMe2 BH2 ]2 but require longer times. Switching the solvent to pyridine induces a remarkable change in the dehydrocoupling product ratio, with (NMe2 )2 BH favoured over [NMe2 BH2 ]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 15â
minutes, though sterically demanding carbonyl substrates require longer times. The mechanisms of these rare examples of Groupâ
1 metal-catalysed processes are discussed.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Chemistry
Journal subject:
QUIMICA
Year:
2017
Type:
Article
Affiliation country:
United kingdom