Nucleophilic substitution at acetylenic carbon. The last holdout

Nickel-catalyzed cross-coupling of primary alkyl halides with phenylethynyl- and trimethylsilyethynyllithium reagents

“…This control experiment proves that nickel-catalyzed coupling is the dominent reaction pathway. Without the participation of the nickel catalyst the possible reaction would be a carbometalationelimination sequence [35,36]. Other combinations of solvents and additives, such as toluene, THF, TMEDA (N,N,N 0 ,N 0 -tetramethylethylenediamine) and KI, led to lower coupling yields (Table 1, entries 1e5, and see supporting information).…”

Application of phase-transfer catalysis (PTC) to reactions of C-H acids with chloroethylenes

“…All these mechanisms were identified in reactions of nucleophiles with TRI or DCA. 23,24 Ethynyl substituted derivative 2c probably results from a halogenophilic attack of any anion present in the system on 4. Dichlorovinylation of nitriles substituted at C-2 with a heteroatom afforded products 3i-m which after unmasking of the carbonyl group should give dichlorovinyl-substituted ketones.…”

Dialkyl 1-Alkynylphosphonates: a Range of Promising Reagents

“…Haloalkynes are triphilic and the approach of anionic and neutral nucleophiles at the haloalkyne has been discussed and appraised in terms of the three sites. [24] Scheme 6 Propargyl bromide reacts with sodium diethyl phosphite 12 to give diethyl 1-propynylphosphonate (18) (R ϭ Et). Unfortunately, irrespective of the reaction conditions (sodium in either refluxing THF [38] or liquid ammonia, [31] potassium carbonate in benzene at 70°C, [39] or potassium fluoride at 60°C without solvent [40] ), complex mixtures containing diethyl 1-propynylphosphonate (18) (R ϭ Et), diethyl 2-propynylphosphonate, and diethyl allenylphosphonate 17 (R ϭ Et, R 1 ϭ R 2 ϭ R 3 ϭ H) are obtained.…”