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Please login to access the full content or check if you have access via20.5.1.2.1.4 Variation 4: Direct Condensation of Acids and Alcohols Using Ammonium Salts
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Jain, N. F.; Masse, C. E., Science of Synthesis, (2007) 20, 714.
Another approach to the direct esterification of equimolar quantities of a given carboxylic acid and alcohol makes use of an ammonium catalyst system to accelerate the reaction. Diphenylammonium trifluoromethanesulfonate is a highly efficient catalyst (1–10 mol%) for the direct condensation of carboxylic acids with a variety of alcohols under mild conditions.[4] In particular, treatment of 3-phenylpropanoic acid with a series of alcohols in the presence of diphenylammonium trifluoromethanesulfonate (1 mol%) in toluene at 80°C affords the corresponding esters 5 in high yields (89–96%). The reaction is tolerant of both primary alcohols and sterically hindered secondary alcohols, although prolonged reaction times are needed for the latter substrates (Scheme 4). Numerous functional groups, including alkenes, halogens, ketones, and cyclopropanes, are well tolerated under the mild reaction conditions. Additionally, the reaction proceeds in high yields in the absence of any dehydrating agents.
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M8 | Meeeeeee (eee%) | Meee (e) | Meeee (%) | Mee |
---|---|---|---|---|
(MM8)8Me | 8 | 8 | 88 | [8] |
(MM8)8MM=MM8 | 8 | 8 | 88 | [8] |
(MM8)8Me | 8 | 8 | 88 | [8] |
(MM8)8Me | 8 | 8 | 88 | [8] |
(MM8)8Me | 8 | 8 | 88 | [8] |
8 | 88 | 88 | [8] | |
MM(Me)(MM8)8Me | 8 | 88 | 88 | [8] |
88 | 88 | 88 | [8] |
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Meeee 8-Meeeeeeeeeeeeeee [8, M8 = (MM8)8Me]; Meeeeee Meeeeeeee:[8]
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References
[4] | Meeeeeee, M.; Meeeee, M.; Meeeee, M.; Meeeee, M., Meeeeeeeeee Meee., (8888) 88, 8888. |