Alkenyl and Alkynyl Compounds

Alkenyl and Alkynyl Compounds.— An ab initio study [4-3IG and 6-3IG basis sets] was made on vinyl-lithium (a classical structure was indicated) and LijCgHa. The most stable CgH2Li2 isomer had a highly distorted partially bridged structure [Z CCLi 87 °] (8). A CNDO/2 calculation established cij-crotyl-lithium as being 31.2 kcal mol more stable than the rraas-isomer.  

A r-bridged structure, rather than rapid equilibrating cr-bonded unsym-metrical structures for allyl-lithium were indicated from the C n.m.r. spectrum of allyl-lithium-ld in THF using the Saunders isotopic perturbation method. However, in one study a symmetric Ji-bridged structure was proposed in contrast to a non-symmetric i-bridged structure in another. 2-R-allyl-(R=Pr or Bu ), crotyl-, or prenyl-potassium, symmetric -complexes result in EtjO or THF. The H n.m.r. and u.v. spectra of allyl-,M+ (M=Na, K, Rb, or Cs) were reported. 

Lapouyade, B. Labrande, and H. Bouas-Laurent, Tetrahedron Lett., 1980, 21, 153. 

Factors influencing the mono and di-metallation of ArCHgC CH and arylallenes by KNH2 in liquid NH3 were studied.  

Sigmatropic 1,2-shifts of acetylenic groups in RC=CCPh2CH2Li (R=Me or Bu ), produced from RC=CCPh2CH2Cl and Li at -75 °C occurs in THF at 0 C [equation (4a)] in contrast the caesium derivative, prepared analogously, rearranges to (11) [equation (46)]. Metallations of allyl benzyl thioether. 

Organic substituents (either Et or -(CH2)5-) and THF coordinated to the Li atoms have been omitted for clarity. 

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Table 3.9. Two Bond Coupling Constants 2JCH of Selected Alkyl, Alkenyl, and Alkynyl Compounds. ...

D. Complexes with a-donor/7i-acceptor ligands 1. Alkenyl and alkynyl compounds... 

Other pseudo-halides are used for carbonylation. Phenyl tluorosulfonate (484) can be carbonylated to give benzoate[337]. Aryl(aryl)iodonium salts[338], aryl(alkenyl)iodonium salts (485)[339], and arylialkynyl)iodonium salts (486)[340] are reactive compounds and undergo carbonylation under mild conditions (room temperature, 1 atm) to give aryl, alkenyl, and alkynyl esters. lodoxybenzene (487) is carbonylated under mild conditions in... 

Aryl chlorides can also be used as coupling partners for azabismocine reagents 2. In the coupling reaction with aryl chlorides, Pd(PPh3)4 was not an efficient catalyst, and Pd(OAc)2/l,l,-bis(diphenylphosphino)ferrocene (dppf) combination was found to be effective [54]. Not only the arylation, but also methylation, alkenylation and alkynylation reactions can be accomplished by using the corresponding bismuth compounds (Scheme 35). The addition of CsF improved the product yields. However, electron-rich aryl chlorides were unable to be coupled efficiently under these reaction conditions. 

It should be emphasized that in some cases the insertions take place several times sequentially. For example, in carbonylation, the insertion of alkene is followed by CO insertion. Sometimes, further insertions of another alkene and CO take place. Particularly useful is the formation of polycyclic compounds by intramolecular sequential insertions of alkenyl and alkynyl bonds. 

A variety of substituted benzenes are known that have one or more of the hydrogen atoms of the ring replaced with other atoms or groups. In almost all of these compounds the special properties associated with the benzene nucleus are retained. A few examples of benzenoid hydrocarbons follow, and it will be noticed that the hydrocarbon substituents include alkyl, alkenyl, and alkynyl groups. Many have trivial names indicated in parentheses ... 

Alkenyl and alkynyl R4Pb and RePb2 compounds tend to be less stable thermally than alkyl analogs. Furthermore, they also exhibit poorer hydrolytic stability and stability to air. Thus, tetravinyllead is sensitive to water. The failure to successfully isolate tetraallyllead may be as much due to its hydrolytic and air instability as to its thermal instability. Alkyl and aryl derivatives which are substituted extensively with fluorine atoms also tend to be hydrolytically unstable, particularly... 

Arylations, Alkenylations and Alkynylations of Neutral Organocopper Compounds II... 

Because of the multitude and diversity of iodonium salts and zwitterions, some of which are labile or are prepared for specific purposes, their preparative methods are discussed in Chapter 8, for diaryl iodonium salts and related compounds, Chapter 9 for perfluoroalkyl, alkenyl and alkynyl phenyliodonium salts and Chapter 10 for zwitterionic iodonium compounds. In addition, the preparation of some lesser known reagents, including 2-iodosylbenzoic acid, is given in Chapter 12. 

Studies of alkenyl- and alkynyl-imidazoles in recent years have increased because of the interest in the polymerization of these compounds under the influence of free radical initiators. 

Physical and chemical data on the MR2L, (R = Me, Et, Ph, allyl, alkenyl, and alkynyl) and MXR(L) (R = Bu, Ph, tolyl X = halide) compounds are greatly lacking, owing to these compounds generally poor thermal stability. The aryl MXR(L) and alkynyl MR2L compounds constitute the most stable classes.The compounds decrease in stability Ba < Sr and XR(L),j compounds form most readily for — I... 

Organocerium reagents are prepared in situ by the reaction of organolithium compounds with anhydrous cerium chloride or ceriiun iodide, as shown in equation (1). A variety of organolithium compounds can be employed, including alkyl-, allyl-, alkenyl- and alkynyl-lithiums, which are all converted to the corresponding cerium reagents. 

Within the same series the unsaturated al-lyl, alkenyl, and alkynyl derivatives are more hypnotic than the saturated analogs with the same number of carbon atoms. Compounds bearing alicyclic or aromatic substituents are more potent than those having aliphatic substituents with the same number of carbons. 

So far as possible, the same order has been used for the fluoroalkyl derivatives in each group of transition metals a-bonded alkyl, alkenyl, and alkynyl derivatives, 7r-bonded derivatives, and then derivatives bonded via N, P, O, or S in that order. In some cases, notably olefin complexes, there is ambiguity about the bonding and this should be borne in mind when searching for particular compounds. Fluoroaryl and heteroaryl derivatives form a more homogeneous group of compounds, and their parameters are considered together across the transition series. 

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