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Issue 5, 2021
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Tri-insertion with dearomatization of terminal arylalkynes using a carborane based frustrated Lewis pair template

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Abstract

Intramolecular vicinal Frustrated Lewis Pairs (FLPs) have played a significant role in the activation of small molecules, and their stabilities and reactivities are found to strongly depend on the nature of the bridging units. This work reports a new carborane based FLP, 1-PPh2-2-BPh2-1,2-C2B10H10 (2), which reacts with an equimolar amount of p-R2NC6H4C[triple bond, length as m-dash]CH (R = Me, Et, Ph) at room temperature to give C[triple bond, length as m-dash]C triple bond addition products 1,2-[PPh2C(R2NC6H4)[double bond, length as m-dash]CHBPh2]-1,2-C2B10H10 (3) in high yields. Compounds 3 react further with two equiv. of p-R2NC6H4C[triple bond, length as m-dash]CH (R = Me, Et) at 60–70 °C to give unprecedented stereoselective tri-insertion products, 3,3a,6,6a-tetrahydronaphtho[1,8a-b]borole tricycles (4), in which one of the aryl rings from arylacetylene moieties has been dearomatized with the formation of four stereocenters including one quaternary carbon center. It is noted that the phosphine unit functions as a catalyst during the reactions. After trapping and structural characterization of a key intermediate, a reaction mechanism is proposed, involving sequential alkyne insertion and 1,2-boryl migration.

Graphical abstract: Tri-insertion with dearomatization of terminal arylalkynes using a carborane based frustrated Lewis pair template

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Article information


Submitted
19 Oct 2020
Accepted
27 Nov 2020
First published
28 Nov 2020

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2021,12, 1745-1749
Article type
Edge Article

Tri-insertion with dearomatization of terminal arylalkynes using a carborane based frustrated Lewis pair template

J. Zhang and Z. Xie, Chem. Sci., 2021, 12, 1745
DOI: 10.1039/D0SC05755J

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