8388 5.3. Formation of acetals catalyzed by bismuth(III) triflate 8388 5.4. Formation of 1,l-diacetates (acylals) 8389 5.5. Cleavage of epoxides catalyzed by bismuth(III) chloride 8389 5.6. Glycosylation promoted by bismuth(III) chloride 8389 5.7. Selective hydrolysis of aryl esters using bismuth(III) mandelate 5.8. Carbon-sulfur bond formation 5.8.1. Synthesis of thioacetals 8389 5.8.2. Conversion of epoxides to thiiranes 8390 5.9. Sulfonylation of aromatics 8390 5.10. Synthesis of sulfides and selenides promoted by Sm-BiCI3 8391 5.11. Synthesis of allyl sulfides 8391 5. 12. Formation of carbon-halogen bonds 8391 5.12.1. Synthesis of �-haloketones and esters 8391 5.12.2. Chlorination of alcohols catalyzed by bismuth(III) salts 8391 5.12.3. Synthesis of peracetylated glycosyl halides 8392 6. Reductions with bismuth compounds 8392 6.1. Selective reduction of nitro compounds to azoxy compounds 8392 6.2. Reduction of nitro compounds to amines 8392 6.3. Chemoselective reduction of a,�-unsaturated ethyl esters using BiCI3-NaBH 4 8392 6.4. Reduction of aromatic a-haloketones 8393 6.5. Miscellaneous reductions 8393 7. Rearrangements promoted by bismuth(III) salts 8393 7.1. Rearrangement of epoxides 8393 7.2. Allylic rearrangement of glycols (the Ferrier rearrangement) 8394 8. Conclusions

Acetals are obtained in good yields by treatment of aldehydes and ketones with trialkyl orthoformate and the corresponding alcohol in the presence of 0.1 mol % Bi(OTf)3.4H2O. A simple procedure for the formation of acetals of diaryl ketones has also been developed. The conversion of carbonyl compounds to the corresponding 1,3-dioxolane using ethylene glycol is also catalyzed by Bi(OTf)3.4H2O (1 mol %). Two methods, both of which avoid the use of benzene, have been developed.

The chemoselective allylation of acetals using allyltrimethylsilane in ionic liquids is catalyzed by TMS triflate (5.0-20.0 mol %). The reaction proceeds smoothly at room temperature to afford the corresponding homoallyl ether in good yield. Since the ionic liquids are easily recovered and recycled, they are a useful alternative to dichloromethane, which is the commonly used solvent for allylations. [reaction--see text]

Aryl-substituted epoxides undergo smooth rearrangement in the presence of 0.01-0.1 mol% Bi(OTf)3,xH20. The rearrangement is regioselective with aryl-substituted epoxides, and products arise from cleavage of the benzylic (-0 bond. The highly catalytic nature of this method coupled with the fact that the reagent is relatively non-toxic, easy to handle and inexpensive make it an attractive alternative to more corrosive and toxic Lewis acids, such as BF3' Et20, currently used to effect epoxide rearrangements.

A method for the in situ formation of N-trifluoroacetoxy succinimide (TFA-NHS) and its application in the formation of succinimidyl esters is presented. The developed method provides N-trifluoroacetyl and N-maleoyl amino acid succinimidyl esters from a variety of amino acids using a one-pot, high-yielding protocol. Investigations into the formation of an N-maleoyl amino acid succinimidyl ester supported the proposal of a revised reaction mechanism, and contributed to the optimization of the reaction conditions.