1-Alkali-metal-2-alkyl-1,2-dihydropyridines: soluble hydride surrogates for catalytic dehydrogenative coupling and hydroboration applications

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Abstract

Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1-lithium-2-t-butyl-1,2-dihydropyridine (1tLi) functions as a precatalyst to convert Me2NH·BH3 to [NMe2BH2]2 (89% conversion) under competitive conditions (2.5 mol%, 60h, 80°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 dehydrocoupling product ratio, with (NMe2)2BH 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.
LanguageEnglish
Pages16853-16861
Number of pages9
JournalChemistry - A European Journal
Volume23
Issue number66
Early online date21 Sep 2017
DOIs
Publication statusPublished - 27 Nov 2017

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Dihydropyridines
Alkali Metals
Lithium
Hydrides
Toluene
Hydrocarbons
Ketones
Aldehydes
Potassium
Solubility
Metals
Sodium
Substrates
1,4-dihydropyridine
lithium bis(trimethylsilyl)amide
4,4,5,5-tetramethyl(1,3,2)dioxaborolane
pyridine

Keywords

  • soluble hydride surrogates
  • 1-lithium-2-t-butyl-1,2-dihydropyridine
  • 1tLi

Cite this

@article{4f8ac8a76ae44a998dab1a392b4937d9,
title = "1-Alkali-metal-2-alkyl-1,2-dihydropyridines: soluble hydride surrogates for catalytic dehydrogenative coupling and hydroboration applications",
abstract = "Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1-lithium-2-t-butyl-1,2-dihydropyridine (1tLi) functions as a precatalyst to convert Me2NH·BH3 to [NMe2BH2]2 (89{\%} conversion) under competitive conditions (2.5 mol{\%}, 60h, 80°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 dehydrocoupling product ratio, with (NMe2)2BH 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.",
keywords = "soluble hydride surrogates, 1-lithium-2-t-butyl-1,2-dihydropyridine, 1tLi",
author = "Ross McLellan and Kennedy, {Alan R.} and Mulvey, {Robert E.} and Orr, {Samantha A.} and Robertson, {Stuart D.}",
note = "This is the peer reviewed version of the following article: McLellan, R., Kennedy, A. R., Mulvey, R. E., Orr, S. A. and Robertson, S. D. (), 1-Alkali-metal-2-alkyl-1,2-dihydropyridines: soluble hydride surrogates for catalytic dehydrogenative coupling and hydroboration applications. Chem. Eur. J., which has been published in final form at https://doi.org/10.1002/chem.201703609. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.",
year = "2017",
month = "11",
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language = "English",
volume = "23",
pages = "16853--16861",
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T2 - Chemistry - A European Journal

AU - McLellan, Ross

AU - Kennedy, Alan R.

AU - Mulvey, Robert E.

AU - Orr, Samantha A.

AU - Robertson, Stuart D.

N1 - This is the peer reviewed version of the following article: McLellan, R., Kennedy, A. R., Mulvey, R. E., Orr, S. A. and Robertson, S. D. (), 1-Alkali-metal-2-alkyl-1,2-dihydropyridines: soluble hydride surrogates for catalytic dehydrogenative coupling and hydroboration applications. Chem. Eur. J., which has been published in final form at https://doi.org/10.1002/chem.201703609. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

PY - 2017/11/27

Y1 - 2017/11/27

N2 - Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1-lithium-2-t-butyl-1,2-dihydropyridine (1tLi) functions as a precatalyst to convert Me2NH·BH3 to [NMe2BH2]2 (89% conversion) under competitive conditions (2.5 mol%, 60h, 80°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 dehydrocoupling product ratio, with (NMe2)2BH 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.

AB - Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1-lithium-2-t-butyl-1,2-dihydropyridine (1tLi) functions as a precatalyst to convert Me2NH·BH3 to [NMe2BH2]2 (89% conversion) under competitive conditions (2.5 mol%, 60h, 80°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 dehydrocoupling product ratio, with (NMe2)2BH 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.

KW - soluble hydride surrogates

KW - 1-lithium-2-t-butyl-1,2-dihydropyridine

KW - 1tLi

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U2 - 10.1002/chem.201703609

DO - 10.1002/chem.201703609

M3 - Article

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