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Witulski, B.; Alayrac, C., Science of Synthesis, (2006) 24, 921.
Methyl esters can be converted in three steps into 2-aryl- or 2-alkyl-1-chloroacetylenes 34 in overall yields of 56–59% (Scheme 21).[76] These transformations involve the coupling of the lithium derivative of chloromethyl 4-tolyl sulfoxide with the methyl esters in tetrahydrofuran at −70°C, and afford the corresponding α-chloro α-sulfinyl ketones 32. These ketones are then subjected to enol trifluoromethanesulfonation, which proceeds smoothly at room temperature using N-phenylbis(trifluoromethanesulfonimide) as the reagent in 1,2-dimethoxyethane solution containing hexamethylphosphoric triamide. The resulting enol trifluoromethanesulfonates 33 undergo desulfinylative β-elimination when treated with butyllithium for a very short time (2 min) at −100°C. Attempts to apply this method to the syntheses of 1-fluoroalk-1-ynes failed.
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References
[76] | Meeee, M.; Meee, M.; Meeeeeee, M.; Meeeeee, M.; Meeeeeee, M., Meee. Meee., (8888), 888. |
[78] | Meeee, M.; Meee, M.; Meeeeeee, M.; Meeee, M.; Meeeeee, M.; Meeeeee, M.; Meeeeeee, M., Meeeeeeeeee, (8888) 88, 8888. |