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. 2018 Dec 10;57(50):16564-16568.
doi: 10.1002/anie.201811783. Epub 2018 Nov 15.

CuI -Mediated Bromoalkynylation and Hydroalkynylation Reactions of Unsymmetrical Benzynes: Complementary Modes of Addition

Xiao Xiao  1 , Tao Wang  1 , Feng Xu  1 , Thomas R Hoye  1
Affiliations

CuI -Mediated Bromoalkynylation and Hydroalkynylation Reactions of Unsymmetrical Benzynes: Complementary Modes of Addition

Xiao Xiao et al. Angew Chem Int Ed Engl. .

Abstract

Benzynes formed by heating a suitable triyne (or tetrayne) substrate are shown to react with in situ generated alkynyl copper species. The latter are compatible with the polyyne substrates and two types of chemistries have been achieved: (i) 1-bromo-1-alkynes efficiently undergo net bromoalkynylation of the (unsymmetrical) benzynes and (ii) in situ generated alkynylcopper species give rise to hydroalkynylation products. The regiochemical preferences of these two modes of reaction are complementary to one another with respect to the position of alkynyl substituent in the final products.

Keywords: alkynylations; aryne trapping; copper; homogeneous catalysis.

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Figures

Figure 1.
Figure 1.
[a] Previous reports by Yoshida et al. [b] This work.
Figure 2.
Figure 2.
[a] Scope of the bromoalkynylation reaction. [b] Proposed catalytic cycle and basis for assignment of the constitution of 12a (cf. 20).
Figure 3.
Figure 3.
Potential synthetic applications [see Supporting Information (SI) for more experimental details].
Figure 4.
Figure 4.
[a] Scope of the hydroalkynylation reaction revealed by outcomes with various alkynes and benzyne precursors. [b] Cu-catalyzed hydroalkynylation occurs faster than other potential aryne trapping reactions; in the absence of catalyst, aryl ether 31 is the major product.
Figure 5.
Figure 5.
Proposed initiation event(s) and catalytic cycle for the hydroalkynylation reaction.
See this image and copyright information in PMC

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