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35.1.1.3.5.2 Method 2: Chlorodecarboxylation of Silver Salts of Carboxylic Acids

DOI: 10.1055/sos-SD-135-00001

Margaretha, P.Science of Synthesis Knowledge Updates, (20142414.

One drawback of the classic Hunsdiecker reaction is the preparation of strictly anhydrous silver salts as starting materials and a second disadvantage is the use of gaseous chlorine as the chlorinating agent. Very recently, a catalytic variation of this reaction has been developed wherein the carboxylic acid 4 is treated with catalytic amounts (5 mol%) of silver(I) trifluoromethanesulfonate–bis(1,10-phenanthroline) complex and equimolar amounts of tert-butyl hypochlorite in acetonitrile.[‌2‌] Whereas tertiary alkyl and benzylic carboxylic acids are converted into the corresponding chloroalkanes at room temperature in about 3 hours, secondary alkyl carboxylic acids react somewhat more slowly (≈ 15 h) under these conditions. In contrast, primary alkyl carboxylic acids are much less reactive, but can be cleanly converted into the corresponding chloroalkanes 5 by increasing the amount of silver catalyst to 10 mol % and by running the reaction at 45 °C. Examples and yields for such reactions are summarized in Scheme 3.

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M8 eee% ee Meeeeeee Meee (°M) Meee (e) Meeee (%) Mee
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8-MeM8M8MM8 8 88 8 88 [‌8‌]
8-MeeMM8 8 88 8 88 [‌8‌]
8-MeM8M8MM8 8 88 8 88 [‌8‌]
MMMe(MM8)88Me 8 88 88 88 [‌8‌]
MM(MM8Me)8 8 88 88 88 [‌8‌]
MMMeMe 8 88 88 88 [‌8‌]
(MM8)88Me 88 88 88 88 [‌8‌]
(MM8)88Me 88 88 8 88e [‌8‌]

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