CC Bond Formation

Name Reactions

Ohira-Bestmann Modification of the Seyfert-Gilbert Homologation

Recent Literature

A highly convenient way to perform the synthesis of alkynes from aldehydes utilizes a new in situ preparation of dimethyldiazomethylphosphonate. As a consequence a commercially available reagent can now be used, circumventing a disadvantage of earlier protocols.
G. J. Roth, B. Liepold, S. G. Müller, H. J. Bestmann, Synthesis, 2004, 59-62.

A direct conversion of activated primary alcohols into terminal alkynes through a sequential one-pot, two-step process involving oxidation with manganese dioxide and then treatment with the Bestmann-Ohira reagent proceeds efficiently under mild reaction conditions with a range of benzylic, heterocyclic and propargylic alcohols.
E. Quesada, R. J. K. Taylor, Tetrahedron Lett., 2005, 46, 6473-6476.

Esters and Weinreb amides undergo reduction to the corresponding aldehydes using DIBAL-H followed by same pot conversion to terminal alkynes utilizing the Bestmann-Ohira reagent in good to excellent yields.
H. D Dickson, S. C. Smith, K. W. Hinkle, Tetrahedron Lett., 2004, 45, 5597-5599.

(Z)-1-Bromo-1-alkenes were stereoselectively efficiently prepared in high yields by microwave irradiation of the corresponding anti-2,3-dibromoalkanoic acids in DMF using Et₃N as base. Microwave-assisted one-pot syntheses of terminal alkynes and enynes from 2,3-dibromoalkanoic acids were also developed.
C. Kuang, Q. Yang, H. Senboku, M. Tokuda, Tetrahedron, 2005, 61, 4043-4052.

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.

Optimized conditions for the Wittig reaction of aldehydes with ethyl tribromoacetate and triphenylphosphine allowed the synthesis of α-bromoacrylates with high selectivity. A simple and efficient one-pot procedure was developed for the preparation of various conjugated acetylenic carboxylates in good yields.
J.-G. Kim, D. H. Kang, D. O. Jang, Synlett, 2008, 443-447.

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.