Synthesis of internal alkynes

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Recent Literature

Terminal and internal acetylenes were obtained in good to excellent isolated yields from carbonyl compounds by converting the carbonyl functionality into the enol nonaflate intermediate followed by elimination to give the C-C triple bond. The one-pot transformations were uniformly induced by phosphazene bases combined with mildly electrophilic nonafluorobutane-1-sulfonyl fluoride.
I. M. Lyapkalo, M. A. K. Vogel, E. V. Boltukhina, J. Vavřík, Synlett, 2009, 558-561.

Tetra-n-butylammonium is a mild and efficient base for the elimination of bromoalkenes. Treatment of 1,1-dibromoalkenes, (Z)-1-bromoalkenes, and internal bromoalkenes with 5 equiv of TBAF • 3 H₂O in DMF yielded terminal and internal alkynes in high yields without problems regarding the presence of water.
M. Okutani, Y. Mori, J. Org. Chem., 2009, 74, 442-444.

A palladium-catalyzed domino coupling reaction of 1,1-dibromo-1-alkenes with triarylbismuth nucleophiles furnishes disubstituted alkynes directly. The couplings are very fast, affording high yields of alkynes in a short reaction time.
M. L. N. Rao, D. N. Jadhav, P. Dasgupta, Org. Lett., 2010, 12, 2048-2051.

The ionic liquid 1-methyl-3-pentylimidazolium fluoroborate, [pmIm]BF₄, is an efficient catalyst as well as solvent for the stereoselective debromination of various vicinal-dibromides to the corresponding (E)-alkenes in high yields under microwave irradiation. This reaction does not require any conventional reducing agent, and the ionic liquid can be recycled.
B. C. Ranu, R. Jana, J. Org. Chem., 2005, 70, 8621-8624.

Dichloroindium hydride (Cl₂InH) generated in situ from the combination of a catalytic amount of indium(III) chloride and sodium borohydride in acetonitrile reduces activated vic-dibromides to the corresponding (E)-alkenes in excellent yields.
B. C. Ranu, A. Das, A. Hajira, Synthesis, 2003, 1012-1014.