With Alkenes and Alkynes

The activation energies for PH3 addition to alkenes were calculated by a simple electrostatic model of point dipoles. Anti-Markownikoff addition was found always to require a higher activation energy than the normal Markownikoff addition [29]. 

The influence of C2H4 on the photolytic decomposition of PH3 was studied [76 to 78]. Reactions of PH3 with some other alkenes yielding mainly primary, not exactly identified phosphanes are given in [33]. 

Dicyclopentadiene reacts with PH3 (mole ratio 3 1) in toluene at 90 C in the presence of AIBN to give a secondary phosphane (viscous yellow oil) of unknown constitution [79]. The addition of PH3 successively to bicyclo[2.2.1]hepta-2,5-diene and 1-octadecene in the presence of AIBN to give a mixture of bicyclic tertiary phosphane isomers is described in [183]. 1,5,9-Cyclododecatriene (90% trans,trans,trans isomer 10% trans,trans,cis isomer) reacts with PH3 on irradiation with °Co radiation at 100 to 140 C to give a mixture of cis and trans isomers of 1 -cyclododeca-4,8-dienylphosphane, 13-phospha-tricyclo[6.4.1.0 ]tridecane, and 13-phospha-tricyclo[7.3.1.0 ]tridecane. The conversion of the cyclodecatriene was 53% [80]. 

Photochemical addition of PH3 to a vinyl-substituted furanose of the type RCH=CH2 produces a mixture of RCH2CH2PH2 and (RCH2CH2)2PH which could not be separated [81]. The photochemical addition to diketene in toluene solution in the presence of AIBN gives methyl(2-oxo-oxetane-4-yl)phosphane and diastereo isomers of methylbis(2-oxo-oxetane-4-yl)phosphane which could not be isolated because of their limited stability [82]. 

AIBN = a,a -azobisisobutyronitrile. - DTBP=di-f-butyl peroxide. - DBP = dibenzoyl peroxide. - HMBG = heptamethyl biguanide. - Z 1 = boron silicate zeolite impregnated with Cr(N03)3. - Z 2 = boron silicate zeolite. 

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The classification of hydrocarbons as aliphatic or aromatic took place m the 1860s when It was already apparent that there was something special about benzene toluene and their derivatives Their molecular formulas (benzene is CgHg toluene is C7Hj ) indicate that like alkenes and alkynes they are unsaturated and should undergo addition reac tions Under conditions m which bromine for example reacts rapidly with alkenes and alkynes however benzene proved to be inert Benzene does react with Bi2 m the pres ence of iron(III) bromide as a catalyst but even then addition isn t observed Substitu tion occurs instead ... 

The Fiiedel-Ciafts alkylation of aiomatics with the lesonance-stabihzed ttichloiocyclopiopenium ttiflate offers a synthetic pathway to ttiaiyl cyclopiopenium salts (26). The ttichloiocyclopiopenium ion has also been shown to undergo Friedel-Crafts reaction with alkenes and alkynes to give trivinyl and tri(halovinyl) cyclopiopenium ions. 

Dibromoborane—dimethyl sulfide is a more convenient reagent. It reacts directly with alkenes and alkynes to give the corresponding alkyl- and alkenyldibromoboranes (120—123). Dibromoborane differentiates between alkenes and alkynes hydroborating internal alkynes preferentially to terminal double and triple bonds (123). Unlike other substituted boranes it is more reactive toward 1,1-disubstituted than monosubstituted alkenes (124). 

Burger s criss-cross cycloaddition reaction of hexafluoracetone-azine (76S349) is also a synthetic method of the [CNN + CC] class. In turn, the azomethines thus produced, (625) and (626) (79LA133), can react with alkenes and alkynes to yield azapentalene derivatives (627) and (628), or isomerize to A -pyrazolines (629) which subsequently lose HCF3 to afford pyrazoles (630 Scheme 56) (82MI40401). 

Monosubstituted hydrazones react with alkenes and alkynic compounds to yield pyrazolidines and pyrazolines, respectively (71LA(743)50, 79JOC218). Oxidation often occurs during the reaction and pyrazoles are isolated as the end product. 

Intramolecular and intermolecular 1,3-dipolar cycloadditions of aziridine-2-car-boxylic esters with alkenes and alkynes have been investigated [131, 132]. Upon heating, aziridine-2-carboxylates undergo C-2-C-3 bond cleavage to form azome-... 

For reactions of A-acyliminium ions with alkenes and alkynes one has to distinguish between A-acyliminium ions locked in an s-trans conformation and those which (can) adopt an s-cis conformation. The former type reacts as a (nitrogen stabilized) carbocation with a C —C multiple bond. Although there are some exceptions, the intramolecular reaction of this type is regarded as an anti addition to the 7t-nucleophile, with (nearly) synchronous bond formation, the conformation of the transition state determining the product configuration. 

E. Reactions of CobalKIII) Porphyrins with Alkenes and Alkynes. 29I... 

This element can never be controlled. Fluorine reacts violently with solid methane at -190°C. With liquid hydrocarbons at -210°C, the reaction is dangerous. All hydrocarbons react dangerously, from the first homologues to anthracene as well as lubricants. In the gaseous state, there is ignition with small quantities, and detonation with large quantities and when the mixture is made quickly. There is immediate detonation with alkenes and alkynes. With benzene, when fluorine is incorporated bubble by bubble and at a low temperature, this causes ignition on the surface. If the flow rate is substantial, there is immediate detonation. 

Scheme 6.10. Photocycloadditions of Enones with Alkenes and Alkynes... 

Nitrones, reactive 1,3-dipoles, react with alkenes and alkynes to form isoxazolidines and isoxazolines, respectively. With monosubstituted olefinic dipolarophiles, 5-substituted isoxazolidines are generally formed predominantly however, with olefins bearing strongly electron-withdrawing groups, 4-substituted derivatives may also be formed.631... 

The photoelimination of carbon dioxide from esters and lactones is a process that has been the subject of detailed investigations. Discussion here is limited to nitrogen containing systems. 3,4-Diphenylsydnone (464), on irradiation in benzene, is converted via the nitrile imine 465 into 2,4,5-triphenyl-1,2,3-triazole (466)388 initial bond formation between N-2 and C-4 followed by loss of carbon dioxide to give the diazirine 467 is proposed to account for the formation of the nitrile imine. Nitrile imines generated in this way have been trapped with alkenes and alkynes to give pyrazoles389... 

Mercury 7r-complexes with alkene and alkyne ligands 447... 

The gas-phase reaction of cationic zirconocene species, ZrMeCp2, with alkenes and alkynes was reported to involve two major reaction sequences, which are the migratory insertion of these unsaturated hydrocarbons into the Zr-Me bond (Eq. 3) and the activation of the C-H bond via er-bonds metathesis rather than /J-hydrogen shift/alkene elimination (Eq. 4) [130,131]. The insertion in the gas-phase closely parallels the solution chemistry of Zr(R)Cp2 and other isoelec-tronic complexes. Thus, the results derived from calculations based on this gas-phase reactivity should be correlated directly to the solution reactivity (vide infra). 

Microwave irradiation promotes the 1,3-dipolar activity of nitrile oxides generated from hydroximoyl chlorides. They interacted in situ over alumina with alkenes and alkynes (150). The effect was demonstrated in reactions of... 

As already indicated, the carbometallation reactions of zirconacyclopropanes and zirconacyclopropenes with alkenes and alkynes are in many ways similar to the corresponding reactions of titanacycles developed more recently. At the same time, however, there are a number of significant differences, as detailed in Section 10.06.2.2. At the present time, synthetically useful carbotitanation reactions are predominantly cyclic and stoichiometric in Ti and more so than the corresponding chemistry of Zr. It seems reasonable to state that Ti and Zr are complementary to each other more often than not. The cyclic carbozirconation may be either stoichiometric or catalytic. Frequently, the difference between the two is that the stoichiometric reactions lack one or more microsteps for completing catalytic cycles. Otherwise, they often share same stoichiometric microsteps. With this general notion in mind, many stoichiometric carbozirconation reactions have indeed been developed into Zr-catalyzed reactions, as discussed later. 

The currently known carbometallation chemistry of the group 6 metals is dominated by the reactions of metal-carbene and metal-carbyne complexes with alkenes and alkynes leading to the formation of four-membered metallacycles, shown in Scheme 1. Many different fates of such species have been reported, and the readers are referred to reviews discussing these reactions.253 An especially noteworthy reaction of this class is the Dotz reaction,254 which is stoichiometric in Cr in essentially all cases. Beyond the formation of the four-membered metallacycles via carbometallation, metathesis and other processes that may not involve carbometallation appear to dominate. It is, however, of interest to note that metallacyclobutadienes containing group 6 metals can undergo the second carbometallation with alkynes to produce metallabenzenes, as shown in Scheme 53.255 As the observed conversion of metallacyclobutadienes to metallabenzenes can also proceed via a Diels-Alder-like... 

Scheme 1.52. Cyclic carbozirconation of three-membered zirconacycles with alkenes and alkynes.

Af-Acyliminium ions are known to serve as electron-deficient 4n components and undergo [4+2] cycloaddition with alkenes and alkynes.15 The reaction has been utilized as a useftil method for the construction of heterocycles and acyclic amino alcohols. The reaction can be explained in terms of an inverse electron demand Diels-Alder type process that involves an electron-deficient hetero-diene with an electron-rich dienophile. Af-Acyliminium ions generated by the cation pool method were also found to undergo [4+2] cycloaddition reaction to give adduct 7 as shown in Scheme 7.16 The reaction with an aliphatic olefin seems to proceed by a concerted mechanism, whereas the reaction with styrene derivatives seems to proceed by a stepwise mechanism. In the latter case, significant amounts of polymeric products were obtained as byproducts. The formation of polymeric byproducts can be suppressed by micromixing. 

In addition to the concerted [2 + 2] cycloadditions of cyclic allenes reported by Elliot and colleagues, Kimura and coworkers22 reported [2 + 2] cycloadditions of several 4-ethenylidene-l,3-oxazolidin-2-ones 35 with alkenes and alkynes (equation 11). The... 

Quaternary ammonium tribromides can also be produced in situ from the quaternary ammonium bromide, sodium hypochlorite and sodium bromide and can be used, for example, in electrophilic addition reactions reaction with alkenes and alkynes. 

In a related smdy, the reactions of a bicyclic dithioether dication (58) (generated from 1,4-dithiane 1-oxide) with alkenes and alkynes has been found to proceed as conjugate addition of two sulfonium groups, giving rise to derivatives of dithioniabicyclo[2.2.2]octane (56) and (57), respectively (Scheme 10). The reaction is sensitive to electronic and steric factors and appears invariably to proceed with retention of the relative arrangement of substiments at the double bond of the original alkene (58). " ... 

The inverse-electron-demand Diels-Alder reaction of 3,6-dichloro[l,2,4,5]tetrazine with alkenes and alkynes provides the synthesis of highly functionalized pyridazines. ° Also, the 4 + 2-cycloaddition reactions of the parent [l,2,4,5]tetrazine with donor-substituted alkynes, alkenes, donor-substituted and unsubstituted cycloalkenes, ketene acetals, and aminals have been investigated. ... 

Difluorophosphoryl(trifluoromethyl) peroxide, 16 135, 136 reactions of, 16 136 Difluoropolysulfanes, 16 302, 325-327 NMR of, 16 325, 326 separation of, 16 327 Difluorosilylene, 29 15-36 alternate layer reactions, 29 26-27 in nuclear recoil systems, 29 22 polymerization, 29 15 reaction mechanisms with alkenes and alkynes, 29 17-19 under co-condensation conditions, 29 28-32, 34-35... 

The theoretical studies showed that the [2 4-2] cydoaddition reactions with alkenes or alkynes were almost barrierless and very exothermic. The exothermicity for alkynes (—42.8 kcal mol ) was found to be greater than that for alkenes (—21.3 kcal mol ). Scheme 4.21b shows the calculated [2 4- 2] cydoaddition with polar unsaturated molecules, formaldehyde and FICN. The barriers (3.6kcalmol for formaldehyde and 9.0 kcal mol for HCN) are slightly higher than those in the reactions with alkenes and alkynes. The exothermicity is also significant (—26.5 for formaldehyde and —37.4 for HCN). 

The electrophile-induced cyclization of heteroatom nucleophiles onto an adjacent alkene function is a common strategy in heterocycle synthesis (319,320) and has been extended to electrophile-assisted nitrone generation (Scheme 1.62). The formation of a cyclic cationic species 296 from the reaction of an electrophile (E ), such as a halogen, with an alkene is well known and can be used to N-alkylate an oxime and so generate a nitrone (297). Thus, electrophile-promoted oxime-alkene reactions can occur at room temperature rather than under thermolysis as is common with 1,3-APT reactions. The induction of the addition of oximes to alkenes has been performed in an intramolecular sense with A-bromosuccinimide (NBS) (321-323), A-iodosuccinimide (NIS) (321), h (321,322), and ICl (321) for subsequent cycloaddition reactions of the cyclic nitrones with alkenes and alkynes. 

Ochiai s landmark paper of 1967, which outlined the basis of the 1,3-APT (Section 1.11.1), also described the reaction of formaldoxime with alkenes and alkynes (284). The oxime 310, behaving as a 1,3-dipole, afforded isoxazolidine cycloadducts 311 through a thermally driven equilibrium (heavily favoring the oxime) in which a proton is transferred from O to N (1,2-prototropy) to afford nitrone 312 (Scheme 1.65). 

Rh-mediated dipolar cycloadditions of diazoquinolinediones 31 with alkenes and alkynes have been investigated. Because of the unsymmetrical nature of the diazo compounds, both linear and angular furoquinoxaline products are possible. In most cases a mixture of tegioisomers was obtained. This methodology has been used for the synthesis of naturally occurring alkaloids, e.g., isodictamnine 32 (R = H) <99JOC3642>. 

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