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. 2021 Feb 10:17:404-409.
doi: 10.3762/bjoc.17.36. eCollection 2021.

Unexpected rearrangements and a novel synthesis of 1,1-dichloro-1-alkenones from 1,1,1-trifluoroalkanones with aluminium trichloride

Beatrice Lansbergen  1 , Catherine S Meister  1 , Michael C McLeod  1
Affiliations

Unexpected rearrangements and a novel synthesis of 1,1-dichloro-1-alkenones from 1,1,1-trifluoroalkanones with aluminium trichloride

Beatrice Lansbergen et al. Beilstein J Org Chem. .

Abstract

A novel reactivity of 1,1,1-trifluoroalkanones is reported, where the reaction with AlCl3 results in the formation of 1,1-dichloro-1-alkenones. The reaction scope was found to be broad, with various chain lengths and aryl substituents tolerated. For substrates containing an electron-rich aromatic ring, further reactions take place, resulting in bicyclic and/or rearrangement products.

Keywords: Friedel–Crafts alkylation; aluminium trichloride; dichloroalkenes; rearrangement; trifluoroalkanes.

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Figures

Figure 1
Figure 1
Examples of biologically active 1,1-dichloro-1-alkenes.
Figure 2
Figure 2
a) Common methods for the preparation of 1,1-dichloro-1-alkenes from aldehydes. b) This work: a two-step synthesis of 1,1-dichloro-1-alkenones from nitriles via 1,1,1-trifluoroalkanones.
Scheme 1
Scheme 1
The initial attempt for the conversion of 1,1,1-trifluoroalkanone 5a to 1,1-dichloroalkenone 6a.
Scheme 2
Scheme 2
Substrate scope for the reaction of 1,1,1 trifluoroalkanones with AlCl3. aPurification (normal or reversed-phase chromatography) required. bComplex mixture. c5 Days.
Scheme 3
Scheme 3
Proposed mechanism for the formation of dichloroalkene 6 from trifluoroalkanone 5.
Scheme 4
Scheme 4
Formation of bicyclic ketones 9 and 10 from 1,1,1-trifluoroalkanone 5b using 7 equivalents of AlCl3.
Scheme 5
Scheme 5
Conversion of 1,1,1-trifluoroalkanone 5n to acid chloride 13 with AlCl3, and possible mechanism.
Scheme 6
Scheme 6
Conversion of 1,1,1-trifluoroalkane 16 to bicycle 17 upon treatment with AlCl3, and possible mechanism.
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