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. 2019 Dec 13;9(1):19113.
doi: 10.1038/s41598-019-55206-7.

Selective synthesis of spirobiindanes, alkenyl chlorides, and monofluoroalkenes from unactivated gem-difluoroalkanes controlled by aluminum-based Lewis acids

Jiandong Wang  1 , Yuta Ogawa  1 , Norio Shibata  2   3
Affiliations

Selective synthesis of spirobiindanes, alkenyl chlorides, and monofluoroalkenes from unactivated gem-difluoroalkanes controlled by aluminum-based Lewis acids

Jiandong Wang et al. Sci Rep. .

Abstract

The highly selective synthesis of spirobiindanes, alkenyl chlorides, and monofluoroalkenes via the cleavage of inert C(sp3)-F bonds in unactivated gem-difluoroalkanes using readily available and inexpensive aluminum-based Lewis acids of low toxicity is reported. The selectivity of this reaction can be controlled by modifying the substituents on the central aluminum atom of the promoter. An intramolecular cascade Friedel-Crafts alkylation of unactivated gem-difluorocarbons can be achieved using a stoichiometric amount of AlCl3. The subsequent synthesis of alkenyl chlorides via F/Cl exchange followed by an elimination can be accomplished using AlEt2Cl as a fluoride scavenger and halogen source. The defluorinative elimination of acyclic and cyclic gem-difluorocarbons to give monofluoroalkenes can be achieved using AlEt3.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Selective defluorination of unactivated gem-difluoroalkanes. (a,b) gem-Difluoro substrates for C–F bond activation (previous work). (c) Selective transformation of gem-difluoro substrates controlled by aluminum reagents (this work).
Figure 2
Figure 2
AlCl3-mediated synthesis of spirobiindanes 2.
Figure 3
Figure 3
AlEt2Cl-mediated synthesis of trisubstituted alkenyl chlorides 3.
Figure 4
Figure 4
AlEt3-mediated synthesis of monofluoroalkenes 4.
Figure 5
Figure 5
Control experiments to investigate possible reaction intermediates (percentage values refer to the NMR yield).
Figure 6
Figure 6
Proposed reaction mechanism.
See this image and copyright information in PMC

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