N-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes

Alkynyl functionalized boron compounds are versatile intermediates in the areas of medicinal chemistry, materials science, and optical materials. In particular, alkynyl boronate esters [R1−C≡C−B(OR2)2]...

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Main Authors:	Richard Böser, Lars Denker, René Frank
Format:	Article
Language:	English
Published:	MDPI AG 2019-04-01
Series:	Molecules
Subjects:	1,3,2-dithioborolane alkynyl boronate <i>N</i>-heterocyclic carbene
Online Access:	https://www.mdpi.com/1420-3049/24/9/1690

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record_format	Article
spelling	doaj-edc5b398a17d4bc48d749a59ed0dd5da2020-11-24T21:49:52ZengMDPI AGMolecules1420-30492019-04-01249169010.3390/molecules24091690molecules24091690<i>N</i>-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-DithioborolanesRichard Böser0Lars Denker1René Frank2Department of Inorganic and Analytical Chemistry, Faculty of Life Sciences, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, GermanyDepartment of Inorganic and Analytical Chemistry, Faculty of Life Sciences, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, GermanyDepartment of Inorganic and Analytical Chemistry, Faculty of Life Sciences, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, GermanyAlkynyl functionalized boron compounds are versatile intermediates in the areas of medicinal chemistry, materials science, and optical materials. In particular, alkynyl boronate esters [R<sup>1</sup>−C≡C−B(OR<sup>2</sup>)<sub>2</sub>] are of interest since they provide reactivity at both the alkyne entity, with retention of the B−C bond or alkyne transfer to electrophilic substrates with scission of the latter. The boron atom is commonly well stabilized due to (i) the extraordinary strength of two B−O bonds, and (ii) the chelate effect exerted by a bifunctional alcohol. We reasoned that the replacement of a B−O for a B−S bond would lead to higher reactivity and post-functionalization in the resulting alkynyl boronate thioesters [R<sup>1</sup>−C≡C−B(S<sub>2</sub>X)]. Access to this poorly investigated class of compounds starts form chloro dithioborolane <i>cyclo</i>-Cl−B(S<sub>2</sub>C<sub>2</sub>H<sub>4</sub>) as a representative example. Whereas syntheses of three coordinate alkynyl boronate thioesters [R<sup>1</sup>−C≡C−B(S<sub>2</sub>X)] proved to be ineffective, the reactions of NHC-adducts (NHC = <i>N</i>-heterocyclic carbene) of <i>cyclo</i>-Cl-B(S<sub>2</sub>C<sub>2</sub>H<sub>4</sub>) afforded the alkyne substituted thioboronate esters in good yield. The products NHC−B(S<sub>2</sub>C<sub>2</sub>H<sub>4</sub>)(C≡C-R<sup>1</sup>) are remarkably stable towards water and air, which suggests their use as boron-based building blocks for applications akin to oxygen-based boronate esters.https://www.mdpi.com/1420-3049/24/9/16901,3,2-dithioborolanealkynyl boronate<i>N</i>-heterocyclic carbene
collection	DOAJ
language	English
format	Article
sources	DOAJ
author	Richard Böser Lars Denker René Frank
spellingShingle	Richard Böser Lars Denker René Frank <i>N</i>-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes Molecules 1,3,2-dithioborolane alkynyl boronate <i>N</i>-heterocyclic carbene
author_facet	Richard Böser Lars Denker René Frank
author_sort	Richard Böser
title	<i>N</i>-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes
title_short	<i>N</i>-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes
title_full	<i>N</i>-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes
title_fullStr	<i>N</i>-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes
title_full_unstemmed	<i>N</i>-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes
title_sort	<i>n</i>-heterocyclic carbene adducts of alkynyl functionalized 1,3,2-dithioborolanes
publisher	MDPI AG
series	Molecules
issn	1420-3049
publishDate	2019-04-01
description	Alkynyl functionalized boron compounds are versatile intermediates in the areas of medicinal chemistry, materials science, and optical materials. In particular, alkynyl boronate esters [R<sup>1</sup>−C≡C−B(OR<sup>2</sup>)<sub>2</sub>] are of interest since they provide reactivity at both the alkyne entity, with retention of the B−C bond or alkyne transfer to electrophilic substrates with scission of the latter. The boron atom is commonly well stabilized due to (i) the extraordinary strength of two B−O bonds, and (ii) the chelate effect exerted by a bifunctional alcohol. We reasoned that the replacement of a B−O for a B−S bond would lead to higher reactivity and post-functionalization in the resulting alkynyl boronate thioesters [R<sup>1</sup>−C≡C−B(S<sub>2</sub>X)]. Access to this poorly investigated class of compounds starts form chloro dithioborolane <i>cyclo</i>-Cl−B(S<sub>2</sub>C<sub>2</sub>H<sub>4</sub>) as a representative example. Whereas syntheses of three coordinate alkynyl boronate thioesters [R<sup>1</sup>−C≡C−B(S<sub>2</sub>X)] proved to be ineffective, the reactions of NHC-adducts (NHC = <i>N</i>-heterocyclic carbene) of <i>cyclo</i>-Cl-B(S<sub>2</sub>C<sub>2</sub>H<sub>4</sub>) afforded the alkyne substituted thioboronate esters in good yield. The products NHC−B(S<sub>2</sub>C<sub>2</sub>H<sub>4</sub>)(C≡C-R<sup>1</sup>) are remarkably stable towards water and air, which suggests their use as boron-based building blocks for applications akin to oxygen-based boronate esters.
topic	1,3,2-dithioborolane alkynyl boronate <i>N</i>-heterocyclic carbene
url	https://www.mdpi.com/1420-3049/24/9/1690
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<i>N</i>-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes

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