Silver iodoacetate

Butenolides.1 When activated by silver trifluoroacetate, this furan is alkylated by primary alkyl iodides or ethyl a-iodoacetate to give 4-alkyl-2-butenolides (2) in 60-80% yield. 

Tin-based reagents are not always snitable owing to the toxicity of organotin derivatives and the difficulties often encountered in removing tin residues from the final product. Therefore, the same authors have carried out additional experiments with 17d and several different alkyl halides under tin-free conditions. The treatment of 16d with tert-butyldiphenylsilyl chloride (TBDPSCl) and triethylamine in the presence of silver triflate in CH2CI2 affords the bis(silyloxy)enamine 17d in 92% yield (Scheme 17). When the radical reaction was carried out with ethyl iodoacetate in the presence of 2,2 -azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as the initiator in CH2CI2, the oxime ether 19 was obtained in 83% yield (Scheme 17). 

Organic Syntheses contains detailed directions656 for preparation of ethyl 2-nitrobutyrate (75 % yield), which can be applied also to other haloalkanoic esters. Ethyl nitroacetate cannot be prepared in this way,657 but is obtained in 77 % yield by the action of silver nitrite on ethyl iodoacetate during several days at room temperature 658 oxidation of ethyl sulfuric acid can also be recommended.659... 

Methyl fluoroacetate was first prepared by Swarts in small yield by the action of silver or mercurous fluoride on methyl iodoacetate. The method is impracticable for large-scale work and therefore the preparation was reinvestigated in detail. Methyl chloroacetate was used in place of the expensive iodoacetate, and a variety of fluorinating agents was tried. It was found that fluorination could be effected by heating methyl chloroacetate in a rotating autoclave with potassium fluoride at 220° for 4 hr. Sodium fluoride, on the other hand, was almost without action. 

Because detailed mechanistic information is not available, a tentative mechanism is proposed here. It is assumed that iodine first adds to the double bond to form an iodonium cation in a process similar to the bromination of alkene, then nucleophilic attack from acetate leads to the formation of the ra/25 -o -iodoacetate. In the presence of silver acetate, a-iodo leaves to give a dioxoanyl carbocation, which is attacked by the second acetate anion to give 1,2-diacetate. Upon hydrolysis or LiAlH4 reduction, diacetate is transformed into trans-l,2-diol. The displayed mechanism is similar to the one proposed by Sudalai. ... 

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