Bismuth(III) Chloride and Triflate: Novel Catalysts for Acylation and Sulfonylation Reactions. Survey and Mechanistic Aspects

Abstract

Acylation and sulfonylation reactions catalyzed by bismuth(III) chloride or triflate are reviewed. For Friedel-Crafts reactions the mechanistic study reveals the different behavior of Bi(OTf)₃, depending on the electrophilic agent used; either that of Lewis acid (with acid anhydrides) or that of procatalyst, carrier of triflate groups (with acid chlorides), leading to in situ generation of mixed anhydrides (RCOOTf or RSO₂OTf) responsible for the aromatic electrophilic substitution. Among the metal triflates tested in these reactions, only Ga(III) and In(III) exhibit high activity. Bi(OTf)₃ appears to be superior to other metal triflates known to catalyze the acylation of alcohols using acid anhydrides as reagents. BiCl₃, especially in the presence of a metal iodide, is the only known efficient catalyst for acyldesilylation reactions of allyl- and enoxysilanes. The low cost of bismuth compounds and their low (or absence of) toxicity are emphasized.

• 1 Introduction

• 2 Acylation of Aromatics

• 2.1 Bi(III) Chloride as Catalyst

• 2.1.1 Mechanistic Aspects

• 2.2 Bismuth(III) Triflate as Catalyst

• 2.2.1 Literature Survey of Triflates Used as Catalysts of Friedel-Crafts Acylation

• 2.2.2 Bismuth(III) Triflate as Catalyst. Results

• 2.2.3 Mechanistic Aspects

• 2.2.4 Comparison of the Catalytic Activities of Bi(OTf)₃ and Other Metal Triflates

• 3 Sulfonylation of Aromatics

• 3.1 Bismuth(III) Chloride as Catalyst

• 3.2 Bismuth(III) Triflate as Catalyst

• 3.3 Mechanistic Aspects

• 4 Acyldesilylation of Organosilanes

• 4.1 Acyldesilylation of Allylsilanes

• 4.2 Acyldesilylation of Enoxysilanes

• 5 Acylation of Alcohols

• 6 Conclusion

acylation - alcohols - allylsilanes - bismuth(III) chloride - bismuth(III) trifluoromethanesulfonate - enoxysilanes - Friedel-Crafts - Lewis acids - sulfonylation

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26e

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55

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56b

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78b March J. Advanced Organic Chemistry. Reactions, Mechanisms, and Structure   4th ed.:  Wiley; New York: 1992.  p.980-981  

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79c Sc(OTf)₃: Ishihara K. Kubota M. Kurihara H. Yamamoto H. J. Org. Chem.  1996,  61:  4560 

79d Me₃SiOTf: Procopiou PA. Baugh SPD. Flack SS. Inglis GGA. J. Org. Chem.  1998,  63:  2342 

79e Damen EWP. Braamer L. Scheeren HW. Tetrahedron Lett.  1998,  39:  6081 

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79h Bi(OTf)₃: Orita A. Tanahashi C. Kakuda A. Otera J. Angew. Chem. Int. Ed.  2000,  39:  2877 

80

Mercury (II) triflate [prepared from diphenyl mercury and triflic acid, as Bi(OTf)₃] [56] reveals a good catalytic activity in FC acylation reactions, especially using acid chlorides as reagents. [55]

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