Hydro-alkenyl-addition

Addition of Alkenes and/or Alkynes to Alkenes and/or Alkynes Hydro-alkenyl-addition... 

A general type of chemical reaction between two compounds, A and B, such that there is a net reduction in bond multiplicity (e.g., addition of a compound across a carbon-carbon double bond such that the product has lost this 77-bond). An example is the hydration of a double bond, such as that observed in the conversion of fumarate to malate by fumarase. Addition reactions can also occur with strained ring structures that, in some respects, resemble double bonds (e.g., cyclopropyl derivatives or certain epoxides). A special case of a hydro-alkenyl addition is the conversion of 2,3-oxidosqualene to dammara-dienol or in the conversion of squalene to lanosterol. Reactions in which new moieties are linked to adjacent atoms (as is the case in the hydration of fumarate) are often referred to as 1,2-addition reactions. If the atoms that contain newly linked moieties are not adjacent (as is often the case with conjugated reactants), then the reaction is often referred to as a l,n-addition reaction in which n is the numbered atom distant from 1 (e.g., 1,4-addition reaction). In general, addition reactions can take place via electrophilic addition, nucleophilic addition, free-radical addition, or via simultaneous or pericycUc addition. 

Addition of Conjugated Alkenes to Aldehydes (the Baylis-Hillman Reaction) 6>-Hydro-C-alkenyl-addition... 

Addition reactions. The same reagent system is active in hydroarylation and hydro-alkenylation of aUcynes. The arylsilanes submit the addends and thereby are converted into benzoxasiloles. ... 

In Grignard reactions, Mg(0) metal reacts with organic halides of. sp carbons (alkyl halides) more easily than halides of sp carbons (aryl and alkenyl halides). On the other hand. Pd(0) complexes react more easily with halides of carbons. In other words, alkenyl and aryl halides undergo facile oxidative additions to Pd(0) to form complexes 1 which have a Pd—C tr-bond as an initial step. Then mainly two transformations of these intermediate complexes are possible insertion and transmetallation. Unsaturated compounds such as alkenes. conjugated dienes, alkynes, and CO insert into the Pd—C bond. The final step of the reactions is reductive elimination or elimination of /J-hydro-gen. At the same time, the Pd(0) catalytic species is regenerated to start a new catalytic cycle. The transmetallation takes place with organometallic compounds of Li, Mg, Zn, B, Al, Sn, Si, Hg, etc., and the reaction terminates by reductive elimination. 

Transmetalations starting from alkcnylzirconiurn species, which are obtained by hydro-ziiconation using H(Cl)ZrCp2, are readily accomplished . Ichikawa, Minami and coworkers have elegantly shown that difluorovinylzinc iodide 64 is obtained by the addition of ZrCp2 to the alkenyl tosylate 65 . In situ transmetalation reactions have also been reported. 

C-M bond addition, for C-C bond formation, 10, 403-491 iridium additions, 10, 456 nickel additions, 10, 463 niobium additions, 10, 427 osmium additions, 10, 445 palladium additions, 10, 468 rhodium additions, 10, 455 ruthenium additions, 10, 444 Sc and Y additions, 10, 405 tantalum additions, 10, 429 titanium additions, 10, 421 vanadium additions, 10, 426 zirconium additions, 10, 424 Carbon-oxygen bond formation via alkyne hydration, 10, 678 for aryl and alkenyl ethers, 10, 650 via cobalt-mediated propargylic etherification, 10, 665 Cu-mediated, with borons, 9, 219 cycloetherification, 10, 673 etherification, 10, 669, 10, 685 via hydro- and alkylative alkoxylation, 10, 683 via inter- andd intramolecular hydroalkoxylation, 10, 672 via metal vinylidenes, 10, 676 via SnI and S Z processes, 10, 684 via transition metal rc-arene complexes, 10, 685 via transition metal-mediated etherification, overview,... 

An analogous reaction mode is followed in the 1 2 cross-coupling of 2-bromostyrene with acenaphthylene, which yields a bisannelated tetrahydrofulvene (Scheme 48)J Norbomene can favorably serve as a relay for cascade carbopalladations as the /S-hydride elimination is virtually impossible. The reaction always starts with an alkenyl-or arylpaUadium starter, generated either by oxidative addition of an alkenyl or aryl halide to a paUadium(O) species or by hydro- or carbopalladation of an alkyne, adding to the double bond. With /3-bromostyrene, norbomene can yield the same type of bisannelated tetrahydrofulvene derivative " as with acenaphthylene, but under different reaction conditions can also react with a 2 1 stoichiometry to give a cyclohexadiene-annelated norbomane derivative (Scheme 49). ... 

---