Decarboxylative elimination of enol triflates as a general synthesis of acetylenes.
The enol trifluoromethanesulfonates 4, 8, 12, 17 and 20 of tert-butyl beta-ketodiesters and beta-ketoesters can be hydrolysed to the corresponding carboxylic acids by dissolution in trifluoroacetic acid. The dicarboxylic acids undergo mild decarboxylative elimination to give the acetylenic acids 4 and 9 in aqueous sodium bicarbonate solution at room temperature. Similarly, the monocarboxylic acids give the terminal and mid-chain acetylenes 13, 18, 21, and 24 by refluxing in acetone with potassium carbonate. One of the substituents on the acetylenes can be methyl, primary alkyl, secondary alkyl or ethynyl, and the other can be a carboxylic acid, hydrogen or primary alkyl, but the enol trifluoromethanesulfonates could not be prepared when one of the substituents was tert-butyl, nor when both substituents on the precursor to the acetylene were secondary alkyl.
Fleming
Ian
I
Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, UK. if10000@cam.ac.uk
Ramarao
Chandrashekar
C
D000107:Acetylation; D000114:Acetylene / Q000031:analogs & derivatives* / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D003653:Decarboxylation; D004952:Esters / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008314:Malonates / Q000737:chemistry; D013058:Mass Spectrometry; D008698:Mesylates / Q000737:chemistry*; D015394:Molecular Structure; D013055:Spectrophotometry, Infrared; D020002:tert-Butyl Alcohol / Q000737:chemistry
D002264:Carboxylic Acids; D004952:Esters; D007659:Ketones; D008314:Malonates; D008698:Mesylates; C030290:malonic acid; C012077:trifluoromethanesulfonic acid; D020002:tert-Butyl Alcohol; D000114:Acetylene