Alkadienes addition

The scope of haloaliphatic additions to alkenes has been extended to the preparation of 1,2-bis(perfluoroalkyl)iodoethanes by the addition of perfluoroalkyl iodides tofluoroalkyl alkenes [73] (equation 12) or to alkadienes [14] (equation 13)... 

The addition of 1,3-dipoles to alka-l,3-diynes has been studied in less detail than that to conjugated alkadienes and alkenynes (80UK1801). Conjugated diynes get involved in [2- -3]cycloaddition at the unsubstituted acetylene bond. 

Allylic titanates having an electrofugal leaving group, e.g., trimethylsilyl68 75 - 77, at the 3-position are powerful reagents for the highly stereoselective synthesis of 1-hetero-substituted 3-alkadienes. For the carbonyl addition of the appropriate titanated allyl sulfides ( ) or carbamates ( and ), reliable y-selectivity and anti diastereoselectivity are reported. The... 

Abstract This chapter deals with the methods for the syntheses of 2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives, and some recent results of their biological activity testing. The electrophilic addition to 1,2-alkadiene- and alkatrienephospho-nate derivatives is one of the easiest and fruitful synthetic strategies for obtaining these compounds in preparative amounts. 

The submitted methods for preparation of target compounds based on the electrophilic addition reactions of 1,2-alkadiene- and alkatrienephosphonates show that they are very promising from synthetic point of view. 

Another example of stereoselective radical cation addition was presented by Hirano and co-workers. The reaction of 1,1-diphenyl-l,n-alkadienes employing 1,4-dicyanobenzene as a sensitizer yielded intramolecular tandem cyclization products in up to 60% yield (Scheme 29) [40]. 

Vanadium(V) fluoride converts polyfluoroaromatics into fluorinated cyclohexadienes and cyclohexenes, and reacts with polyfluorinated and polychlorinated alkenes,113 115 alkadienes, cycloalkenes and cyclodienes to give addition products of two fluorine atoms across C = C bonds.116117... 

It is generally agreed that the kinetics and the distributions of deuter-ated products from the reactions of alkynes or alkadienes with deuterium are satisfactorily interpreted in terms of the consecutive addition of two hydrogen atoms, of unspecified origin, to the adsorbed hydrocarbon to yield the monoolefin. The identity of the distributions of deuteroethyl-enes from the reaction of acetylene with equilibrated and non-equil-ibrated hydrogen—deuterium mixtures also provides strong evidence for such a mechanism [91]. 

The properties of a compound with isolated double bonds, such as 1,4-pentadiene, generally are similar to those of simple alkenes because the double bonds are essentially isolated from one another by the intervening CH2 group. However, with a conjugated alkadiene, such as 1,3-pentadiene, or a cumulated alkadiene, such as 2,3-pentadiene, the properties are sufficiently different from those of simple alkenes (and from each other) to warrant separate discussion. Some aspects of the effects of conjugation already have been mentioned, such as the influence on spectroscopic properties (see Section 9-9B). The emphasis here will be on the effects of conjugation on chemical properties. The reactions of greatest interest are addition reactions, and this chapter will include various types of addition reactions electrophilic, radical, cycloaddition, and polymerization. 

The general character of alkene polymerization by radical and ionic mechanisms was discussed briefly in Section 10-8. The same principles apply to the polymerization of alkadienes, with the added feature that there are additional ways of linking the monomer units. The polymer chain may grow by either 1,2 or 1,4 addition to the monomer. With 1,3-butadiene, for example,... 

Conducting the same experiment using tril-inolein produced volatiles unique to the trili-nolein substrate, with the major classes being alkanals, 2-alkenals, 2,4-alkadienals, and hydrocarbons. Those volatiles, produced uniquely from this substrate and attributable to the breakdown of 9- and 13-hydroperoxides, include pentane, pentanal, 1 -pentanol, hexanal, 2-hexenal, 3-hexenal, 2-heptenal, 2-octenal, 2,4-decadienal, and acrolein. Addition of triolein afforded the added production of volatiles previously identified in triolein alone, but ad-... 

ADDITION OF HETEROATOM NUCLEOPHILES TO METAL-ACTIVATED ALKADIENES 565... 

The same transition metal systems which activate alkenes, alkadienes and alkynes to undergo nucleophilic attack by heteroatom nucleophiles also promote the reaction of carbon nucleophiles with these unsaturated compounds, and most of the chemistry in Scheme 1 in Section 3.1.2 of this volume is also applicable in these systems. However two additional problems which seriously limit the synthetic utility of these reactions are encountered with carbon nucleophiles. Most carbanions arc strong reducing agents, while many electrophilic metals such as palladium(II) are readily reduced. Thus, oxidative coupling of the carbanion, with concomitant reduction of the metal, is often encountered when carbon nucleophiles arc studied. In addition, catalytic cycles invariably require reoxidation of the metal used to activate the alkene [usually palladium(II)]. Since carbanions are more readily oxidized than are the metals used, catalysis of alkene, diene and alkyne alkylation has rarely been achieved. Thus, virtually all of the reactions discussed below require stoichiometric quantities of the transition metal, and are practical only when the ease of the transformation or the value of the product overcomes the inherent cost of using large amounts of often expensive transition metals. 

The sequential treatment of ( , )-l-tosylamido-2, 4-alkadienes with n-butyl-lithium and propynyliodonium triflate 30 results in a cascade addition/bicy-clization sequence leading to bicyclic N-tosyldihydropyrroles 39 (Scheme 60) [165,166]. These transformations are completely stereoselective for the cis-isomers, and appear to proceed by intramolecular addition of alkylidenecarbene intermediates to the C2-C3 double bond of the pentadienyl chain to give azabi-cyclo[3.1.0]hexenes, which rearrange to 39 through diyl radical species. 

Catalyzed hydrogenation of alkynes, alkenynes, and alkadienes.1 This catalyst effects highly c/s-selective hydrogenation of triple bonds of alkynes and alkenynes, with easy recovery of the complex by filtration. It also effects only 1,2-addition in hydrogenation of even hindered 1,4-substituted 1,3-butadienes. 

Oguma Y., Nemoto T. and Kuwahara Y. (1992b) A sex pheromone study of a fruit fly Drosophila virilis Sturtevant (Diptera Drosophilidae) additive effect on cuticular alkadienes to major sex pheromone. Appl. Entomol. Zool. 27, 499-505. 

All reactions of Table 9.1 were performed in pyridine, usually at room temperature by addition of water, methanol, acetic acid, etc. it was possible to prepare several functionalized compounds from alkenes and alkadienes. 

In addition to the head-to-head cross-coupling reactions, it has been discovered that the reaction of phenyl or 1-alkenyl iodides with (E)-l-alkenyl-l,3,2-benzo-dioxaboroles produces the head-to-tail cross-coupling products, 2-phenyl-1-alkenes or 2-alkyl-1,3-alkadienes, respectively (Eq. 107) The reaction is profoundly affected by catalytic quantities of palladium compounds (Pd black prepared by reduction of Pd(OAc)j with diborane is especially effective) in the presence of tri-ethylamine. 

This review article deals primarily with addition reactions of nucleophiles, electrophiles, and neutral radicals to photochemically generated radical ions of organic compounds and some organometallic compounds. Photocyclodimerizations of electron-rich alkenes, photo-Diels-Alder reactions between alkenes and alkadienes via dimer or heterodimer radical cations, and photocycloadditions via triplexes are also included. 

As for many other nucleophiles, the nitrite anion undergoes addition to the iodonium ion generated by the reaction of alkenes and 1,3-alkadienes with electrophilic iodine reagents. Two procedures have been described bis(pyridine)iodine(I) tetrafluoroborate136,137 [prepared from mcrcury(II) oxide and tctrafluoroboric acid supported on silica gel and pyridine on dichloromethane] and copper(II) tetrafluoroborate [prepared from copper(II) oxide and te-trafluoroboric acid] and iodine138 139. trans Addition would be expected for all products from mechanistic considerations, however, only the cyclohexene adduct 1 has been shown to have trans configuration ( H-NMR spectroscopy)139. 

The theoretical yield of pyrolysis products calculated on the basis of the additivity of individual plastic pyrolysis at 550°C is in good agreement with the products yields for the mixed plastics pyrolysis. However, with increase of the pyrolysis temperature, the char and gas yield are higher (with a decrease of oil and wax yields), suggesting that there are some interaction of the plastics in the mixture during pyrolysis [8], Increasing the pyrolysis temperature leads to an increase of the aromatics, and a decrease of alkanes, aUcenes and alkadienes in the oils. 

The pyrolysis liquid of Nylon 6,6 contains alkadienes and cycloalkenes in addition to cyclopentanone in the gasoline boiling range, furthermore this fraction also involves hexanedinitrile and even alkylamines. The components of the diesel oil boiling range... 

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