Vinylic halide reactions

Another feature of carbenoid-type reactivity is the cyclopropanation (reaction c). Again, this reaction does not only take place in vinylidene but also in alkyl carbenoids . On the other hand, the intramolecular shift of a /3-aryl, cyclopropyl or hydrogen substituent, known as the Fritsch-Buttenberg-Wiechell rearrangement, is a typical reaction of a-lithiated vinyl halides (reaction d) . A particular carbenoid-like reaction occurring in a-halo-a-lithiocyclopropanes is the formation of allenes and simultaneous liberation of the corresponding lithium halide (equation 3). ... 

Palladium-T riary lphosphine Complexes as Catalysts for Vinylic Halide Reactions... 

Most of the recent developments in the vinyl halide reaction chemistry of lower-order cuprates are of zinc cyanocuprates (RCu(CN)ZnX)24. While only reacting with unfunc-... 

Four oxidation states of palladium are encountered in organometallic chemistry see Palladium Inorganic Coordination Chemistry) In order of importance, they are Pd , Pd , Pd, and Pd . With the reduction of palladium from Pd to Pd , the metal changes its reactivity from electrophile to nucleophile. However, unlike main group nucleophiles such as thiolates or cyanide, Pd complexes react with both alkyl halides and aryl or vinyl halides. Reactions of Pd complexes with these latter sp halides generate new Pd aryl or vinyl bonds through the process of oxidative addition. 

The reaction of vinyl chloride with CD favors the a-route (nucleophilic attack at the a-bond) over the Ti-route (nucleophilic attack at the tt-bond), but vinyl chloride is not an experimentally viable substrate and cannot be considered as representative for the vinyl 8 2 reaction. The tt-route is anticipated in substituted vinylic halide reactions, where electron-withdrawing groups are attached to the vinylic carbon. See Bach, R. D. Baboul, A. G. Schlegel, H. B. J. Am. Chem. Soc, 2001, 123, 5787. 

Reaction with cyclic vinyl halides. Reaction of 2-chlorobicyclo[2.2.1]hep-tene-1 (1) with -butyllithium in THF at 25° gives (2) and (3) as the major products. Experiments with optically inactive and active (1) labeled with deuterium indicate that a symmetrical species is an intermediate in the formation of... 

Vinyl halides. The method of Normant et al. (6, 270) for preparation of vinylcopper compounds can be used to obtain vinyl halides. Reaction of 1 with iodine gives vinyl iodides directly, but this reaction when extended to Bf2 or CI2 gives mainly dimers. The desired vinyl chlorides and bromides canTte obtained with NCS or NBS in fair to good yields. The replacement occurs with retention of initial stereochemistry. The American group also stresses the importance of the purity of the copper salt and uses House s cuprous bromide complex with dimethyl sulfide (6, 270). 

R. F. Heck, Adv. Chem. Ser, 1982, 196, 213-230. Palladium-Triarylphosphine Complexes as Catalysts for Vinylic Halide Reactions. 

Studies reporting substituent effects on the palladium- and copper-catalysed Sonogashira coupling reaction between an aryl iodide and an alkyne the 5 2 allylic substitution reactions between benzyl amine and racemic allyl carbonates substituted with a j -X-Ph- group on C(l) in the presence of a Rh(15,15, 2/ ,2/ -tangphos)(COD)Bp4 catalyst the stereoselective 5 2 reactions between a-substituted linear 0-ketoesters and meta- and /Jura-substituted cinnamyl carbonates generating vicinal quaternary and tertiary stereocenters in the presence of an Ir-V-arylphosphoramidite catalyst, TBD, and LiOBu-t identity vinyl halide reactions the S N... 

G., Photoreactivity of some a-arylvinyl bromides in acetic acid. Selectivity toward bromide versus acetate ions as a mechanistic probe, J. Am. Chem. Soc., 113,4261,1991. See also (b) Kitamura, X, Kabashima, X, Kobayashi, S., and Taniguchi, H., Isolation and alcoholysis of an ipso adduct, vinylidenecyclohexadiene, from photolysis of l-(p-ethoxyphenyl)vinyl bromide. Tetrahedron Lett., 29, 6141, 1988 (c) Kitamura, X, Nakamura, I., Kabashima, X, Kobayashi, S., and Taniguchi, H., A novel spiro adduct from intramolecular ipso substitution in the photolysis of an a-[p-(2-hydroxyalkoxyjphenyl]vinyl bromide,/. Chem. Soc., Chem. Commun., 1154, 1989 (d) Kitamura, X, Kobayashi, S., and Xaniguchi, H., Photolysis of vinyl halides. Reaction of photogenerated vinyl cations with cyanate and thiocyanate ions,/. Org. Chem., 55, 1801, 1990 (e) Hori, K., Kamada,... 

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