Opening reactions with organometallic compounds

Electrophilic Opening 20 Nucleophilic Opening 22 Cyclisation Reactions 26 Reduction and Elimination Reactions 28 Photochemical Reactions 30 Reactions with Organometallic Compounds 30 Miscellaneous Reactions 34... 

A great number of norbornene-like monomers [e.g., m = 1-3, R] and R2 = alkyl and aryl groups, Eqs. (103) and (104)] with or without substituents have been employed in polymerization reactions induced by Ziegler-Natta and ROMP catalysts derived from ruthenium, osmium, iridium, palladium, platinum, molybdenum, and tungsten halides or vanadium and zirconium halides or acetylacetonate associated with organometallic compounds [162, 163]. Both addition and ring-opened polymers have been obtained by this way depending on the catalyst employed [Eqs. (103) and (104)]. 

Employing an excess of the organometallic reagent (2 equiv) at 100 °C resulted in the formation of ketopyrrole (S)-79 in 87% yield. Obviously, compound (S)-79 is produced by successive N-acylation, t>-directed metallation and N,C-acy migration. Nucleophilic ring-opening reaction of the lactone (S)-77 with A -methylpyrrole lithiated in 2-position (with Bu Li/TMEDA) proceeded smoothly furnishing the ketone (S)-79 in 62% yield. 

Precursor of Useful Chiral Ligands. OPEN is widely used for the preparation of chiral ligands. Organometallic compounds with these ligands act as useful reagents or catalysts in asymmetric induction reactions such as dihydroxylation of olefins, transfer hydrogenation of ketones and imines, Diels-Alder and aldol reactions, desymmetrization of meso-diols to produce chiral oxazolidinones, epoxidation of simple olefins, benzylic hydroxylation, and borohydride reduction of ketones, imines, and a,p-unsaturated carboxylates. ... 

Nucleophilic ring-opening of oxiranes by lithium dialkylcuprates occurs at the sterically less-hindered side and the corresponding alcohol is formed.The reaction can be carried out under mOd conditions and the side-reactions observed with other organometallic compounds can be avoided. The mechanism of the transformations has been treated in detail. With MejCuLi the reaction proceeds stereoselectively and the new C-C bond is formed on the side opposite the C-0 bond of the oxirane (Eq. 

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