Alkenylation and Alkynylation

Carbanions are negatively charged organic species with an even number of electrons and the charge mainly concentrated on a carbon atom. In alkyl, alkenyl, and alkynyl anions all of the... 

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... 

Fischer-type carbene complexes, generally characterized by the formula (CO)5M=C(X)R (M=Cr, Mo, W X=7r-donor substitutent, R=alkyl, aryl or unsaturated alkenyl and alkynyl), have been known now for about 40 years. They have been widely used in synthetic reactions [37,51-58] and show a very good reactivity especially in cycloaddition reactions [59-64]. As described above, Fischer-type carbene complexes are characterized by a formal metal-carbon double bond to a low-valent transition metal which is usually stabilized by 7r-acceptor substituents such as CO, PPh3 or Cp. The electronic structure of the metal-carbene bond is of great interest because it determines the reactivity of the complex [65-68]. Several theoretical studies have addressed this problem by means of semiempirical [69-73], Hartree-Fock (HF) [74-79] and post-HF [80-83] calculations and lately also by density functional theory (DFT) calculations [67, 84-94]. Often these studies also compared Fischer-type and... 

Catalyst 11 showed great tolerance for functional groups like rmsaturated carbon-carbon bonds (alkenyl and alkynyl moieties), halides, electron-withdrawing and -donating groups, etc. (Table 4). 

Terminal-functionalized polymers such as macromonomers and telechelics are very important as prepolymer for construction of functional materials. Single-step functionalization of polymer terminal was achieved via lipase catalysis. Alcohols could initiate the ring-opening polymerizahon of lactones by lipase catalyst. The lipase CA-catalyzed polymerizahon of DDL in the presence of 2-hydroxyethyl methacrylate gave the methacryl-type polyester macromonomer, in which 2-hydroxyethyl methacrylate acted as initiator to introduce the methacryloyl group quanhtatively at the polymer terminal ( inihator method ).This methodology was expanded to the synthesis of oo-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator, respechvely. 

Alkenyl and alkynyl Fischer carbene complexes reacted with pyrrole imine 108 to give, through a 1,2- and 1,3-metal migration, respectively, indolizine derivatives at a different level of unsaturation (Scheme 29) <1999JA3065>. 

Fig. 3.26. Conversion of alkenyl and alkynyl complexes into carbene and vinylidene complexes.

The rate constants for methanolysis of alkyl /j-toluenesulfonates conform to a two-parameter equation of the Hammett-Taft type, the governing structural factor being steric hindrance. " However, the alcoholysis rates of alkenyl and alkynyl jo-toluenesulfonates do not obey this relation, probably because the multiple bonds stabilize the reaction intermediate. 

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. 

Reactivity of Substituents Attached to Ring Carbon Atoms 10.11.7.1 Alkyl, Alkenyl, and Alkynyl Derivatives... 

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. 

Examples of intermolecular addition of allenylzinc reagents to carbon—carbon double and triple bonds appear to be restricted to the more reactive alkenyl and alkynyl organometallic species. 

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