Allyl complexes reactions

From previously reported studies then, several different products are possible. The initial attack by the oxygen moiety may apparently be vinylic (on either of the two carbons of the double bond) or allylic (on the carbon next to the doubly bonded carbons). Distinction must be made between allylic attack as described here and allylic products which can arise either by true allylic attack or by vinylic attack followed by olefinic isomerization. Thus it is not clear whether such products as 2-hexen-l-yl acetate(II) (58) have been formed by vinylic attack upon hexene followed by olefinic isomerization, by olefin isomerization of hexene to 2-hexene followed by allylic attack, or by some type of synchronous mechanism in which oxygen attack and olefin isomerization occur simultaneously. This last possibility could be visualized as involving some type of 7r-allylic complex (Reaction 2). This involvement of TT-allylic complex can be ruled out only in the production of isopropenyl acetate from propylene since a mechanism such as this followed by olefin isomerization could not be used in that case. For the butenes and higher... 

Nickel-allyl complexes prepared from Ni(CO)4 and allyl bromides are useful for the ole-fination of alkyl bromides and iodides (E.J. Corey, 1967 B A.P. Kozikowski, 1976). The reaction has also been extended to the synthesis of macrocycles (E.J. Corey, 1967 C, 1972A). 

Reactions Involving Pd(II) Compounds and Pd(0) Complexes ic-Allyl complex formation and its reaction with a nucleophile... 

Typical nucleophiles known to react with coordinated alkenes are water, alcohols, carboxylic acids, ammonia, amines, enamines, and active methylene compounds 11.12]. The intramolecular version is particularly useful for syntheses of various heterocyclic compounds[l 3,14]. CO and aromatics also react with alkenes. The oxidation reactions of alkenes can be classified further based on these attacking species. Under certain conditions, especially in the presence of bases, the rr-alkene complex 4 is converted into the 7r-allylic complex 5. Various stoichiometric reactions of alkenes via 7r-allylic complex 5 are treated in Section 4. 

TT-Aliylpalladium chloride reacts with a soft carbon nucleophile such as mal-onate and acetoacetate in DMSO as a coordinating solvent, and facile carbon-carbon bond formation takes place[l2,265], This reaction constitutes the basis of both stoichiometric and catalytic 7r-allylpalladium chemistry. Depending on the way in which 7r-allylpalladium complexes are prepared, the reaction becomes stoichiometric or catalytic. Preparation of the 7r-allylpalladium complexes 298 by the oxidative addition of Pd(0) to various allylic compounds (esters, carbonates etc.), and their reactions with nucleophiles, are catalytic, because Pd(0) is regenerated after the reaction with the nucleophile, and reacts again with allylic compounds. These catalytic reactions are treated in Chapter 4, Section 2. On the other hand, the preparation of the 7r-allyl complexes 299 from alkenes requires Pd(II) salts. The subsequent reaction with the nucleophile forms Pd(0). The whole process consumes Pd(ll), and ends as a stoichiometric process, because the in situ reoxidation of Pd(0) is hardly attainable. These stoichiometric reactions are treated in this section. 

The intramolecular insertion of a conjugated diene into 7r-allylpalladium, initially formed in 789, generates another rr-allyl complex 790, which is trapped with acetate anion to give a new allylic acetate 791. No further reaction of the allylic acetate with alkene takes place[489]. 

C-Allyl Complex Formation. AHyl hahde, aHyl ester, and other aHyl compounds undergo oxidative addition reactions with low atomic valent metal complexes to form TT-aHyl complexes. This is a specific reaction of aHyl compounds. 

There appear to be few examples of the formation of azetidin-2-ones by closure of the C(2) —C(3) bond. One reaction which fits into this category involves reaction of the iron carbonyl lactone complexes (144) with an amine to give the allyl complexes (145) which on oxidation are converted in high yield to 3-vinyl-/3-lactams (146) (80CC297). 

The application of these catalysts in the initial state (without any special treatment of the surface organometallic complexes of such cata-lysts) for ethylene polymerization has been described above. The catalysts formed by the reaction of 7r-allyl compounds with Si02 and AUOj were found to be active in the polymerization of butadiene as well (8, 142). The stereospecificity of the supported catalyst differed from that of the initial ir-allyl compounds. n-Allyl complexes of Mo and W supported on silica were found to be active in olefin disproportionation (142a). 

Another difference between the two mechanisms is that the former involves 1,2 and the latter 1,3 shifts. The isomerization of 1-butene by rhodium(I) is an example of a reaction that takes place by the metal hydride mechanism, while an example of the TT-allyl complex mechanism is found in the Fe3(CO)i2 catalyzed isomerization of 3-ethyl-l-pentene. " A palladium acetate or palladium complex catalyst was used to convert alkynones RCOCSCCH2CH2R to 2,4-alkadien-l-ones RCOCH= CHCH = CHCHR. ... 

One other reaction deserves mention. From bis(cyclooctadiene)nickel and butadiene (31), and in the presence of an isocyanide (RNC, R = cyclohexyl, phenyl, tcrt-butyl) two organic oligomeric products are obtained, 1 -acylimino-11 -vinyl-3,7-cycloundecadiene and 1 -acylimino-3,7,11 -cyclo-dodecatriene. In each, one isocyanide has been incorporated. An analogous reaction with carbon monoxide had been reported earlier. The proposed mechanism of these reactions, via a bis-7r-allyl complex of nickel, is probably related to the mechanism described for allylpalladium complexes above. 

Catalytic hydrogenation with platinum liberates the hydrocarbon from methylcobalamin (57) and from alkyl-Co-DMG complexes (161), but not from pentacyanides with primary alkyl, vinyl, or benzyl ligands, though the cr-allyl complex yields propylene (109). Sodium sand gives mixtures of hydrocarbons with the alkyl-Co-salen complexes (64). Dithioerythritol will liberate methane from a variety of methyl complexes [cobalamin, DMG, DMG-BF2, G, DPG, CHD, salen, and (DO)(DOH)pn] (156), as will 1,4-butanedithiol from the DMG complex (157), and certain unspecified thiols will reduce DMG complexes with substituted alkyl ligands (e.g., C0-CH2COOH ->CH3C00H) (163, 164). Reaction with thiols can also lead to the formation of thioethers (see Section C,3). 

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