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Synthesis of enynes


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Reaction of readily accessible benzylic and allylic alkyl bromides with iodoform followed by a one-pot double elimination procedure enables a triphenylphosphine-free synthesis of 1-iodoalkynes including facile purification compared with Corey-Fuchs iodoalkynylation conditions. Replacing CHI3 with CHI2Cl allows the isolation of gem-(Z)-chloro-(E)-iodoalkenes. The use of benzhydryl bromides as nucleophiles leads to trisubstituted alkenes.
G. Pelletier, S. Lie, J. J. Mousseau, A. B. Charette, Org. Lett., 2012, 14, 5464-5467.

A simple procedure for the synthesis of substituted (E)-2-alkene-4-ynecarboxylic esters has been achieved using hydroxyapatite-supported palladium as efficient catalyst surface. The highly efficient catalyst can be recycled.
B. C. Ranu, L. Adak, K. Chattopadhyay, J. Org. Chem., 2008, 73, 5609-5612.

An efficient, palladium-catalyzed synthesis of 2-alkene-4-ynoates and -nitriles by a simple reaction of vic-diiodo-(E)-alkenes with acrylic esters and nitriles in water leads to (E)-isomers from acrylic esters exclusively, whereas (Z)-isomers are obtained in high stereoselectivity from reactions of acrylonitrile. The in situ prepared Pd(0) nanoparticles can be recycled.
B. C. Ranu, K. Chattopadhyay, Org. Lett., 2007, 9, 2409-2412.

B. C. Ranu, K. Chattopadhyay, Org. Lett., 2007, 9, 2409-2412.

Deprotonation of 3,3,3-trichloropropyl-1-triphenylphosphonium chloride generates the corresponding phosphorane, which reacts with aldehydes to give trichloromethylated (Z)-olefins, which are useful for the synthesis of (Z)-1,3-enynes, (Z,Z)-1-chloro-1,3-dienes, and 1,3-diynes in high yields and stereospecificities.
M. S. Karatholuvhu, P. L. Fuchs, J. Am. Chem. Soc., 2004, 126, 14314-14315.

Highly regio- and stereoselective reactions of readily available 2-(methoxycarbonyl)-2,3-allenols with oxalyl chloride in the presence of Et3N or DMSO afforded methyl 2-(ethynyl)alk-2(E)-enoates and 2-(1′-chlorovinyl)alk-2(Z)-enoates, respectively, in good yields.
Y. Deng, X. Kin, C. Fu, S. Ma, Org. Lett., 2009, 11, 2169-2172.

(E)-α-Ethynyl-α,β-unsaturated esters were prepared in good yields from allenyl acetates by treatment with 10 mol % DABCO in DMF at room temperature.
Y. Choe, P. H. Lee, Org. Lett., 2009, 11, 1445-1448.