Of organometallic compounds

Hard carbon nucleophiles of organometallic compounds react with 7r-allyl-palladium complexes. A steroidal side-chain is introduced regio- and stereo-selectively by the reaction of the steroidal 7T-allylpalladium complex 319 with the alkenylzirconium compound 320[283]. 

In addition, a catalytic version of Tt-allylpalladium chemistry has been devel-oped[6,7]. Formation of the Tr-allylpalladium complexes by the oxidative addition of various allylic compounds to Pd(0) and subsequent reaction of the complex with soft carbon nucleophiles are the basis of catalytic allylation. After the reaction, Pd(0) is reformed, and undergoes oxidative addition to the allylic compounds again, making the reaction catalytic.-In addition to the soft carbon nucleophiles, hard carbon nucleophiles of organometallic compounds of main group metals are allylated with 7r-allylpalladium complexes. The reaction proceeds via transmetallation. These catalytic reactions are treated in this chapter. 

The stereochemistry of the Pd-catalyzed allylation of nucleophiles has been studied extensively[5,l8-20]. In the first step, 7r-allylpalladium complex formation by the attack of Pd(0) on an allylic part proceeds by inversion (anti attack). Then subsequent reaction of soft carbon nucleophiles, N- and 0-nucleophiles proceeds by inversion to give 1. Thus overall retention is observed. On the other hand, the reaction of hard carbon nucleophiles of organometallic compounds proceeds via transmetallation, which affords 2 by retention, and reductive elimination affords the final product 3. Thus the overall inversion is observed in this case[21,22]. 

The properties of organometallic compounds are much different from those of the other classes we have studied to this point Most important many organometallic com pounds are powerful sources of nucleophilic carbon something that makes them espe cially valuable to the synthetic organic chemist For example the preparation of alkynes by the reaction of sodium acetylide with alkyl halides (Section 9 6) depends on the presence of a negatively charged nucleophilic carbon m acetylide ion... 

A large number of organometallic compounds are based on transition metals Examples include organic derivatives of iron nickel chromium platinum and rhodium Many important industrial processes are catalyzed by transition metals or their complexes Before we look at these processes a few words about the structures of transition metal complexes are m order... 

Chapman and Hall Chemical Database Chapman and Hall, Ltd. Dialog Dictiona of Organic Compounds (5th ed.), Dictiona of Organometallic Compounds, Carbohydrates, Mmino Mcids, Peptides, Dictionay of Antibiotics and Eelated Compounds, and Dictionay of Organophosphorus Compounds... 

T. G. Brihnka and V. A. Shushunov, Reactions of Organometallic Compounds with Ouygen and Peroxide, CRC Press, Inc., Cleveland, Ohio, 1969, pp. 184-185. 

F. E. Btinckman and G. Gordon, Proceedings of the International Symposium on Decomposition of Organometallic Compounds to Eefractoy Ceramics, Metals, and Metal Alloys, Dayton, Ohio, 1967. 

Reaction of organometallic compounds with enamine salts have been successfully used for the synthesis of some natural products (256). Thus reaction of the immonium salt of 0-alkylated enamino ketone 122 with isobutyllithium affords the compound 169. 

In the case of organometallic compounds the most satisfactory way of classifying the ligands... 

Another such effect is the intervention of cyclic transition states in reactions of organometallic compounds (Section II, B, 5) with azines or in intramolecular nucleophilic substitutions (Section II, F). 

Furan is typically tiVC) coordinated in a series of organometallic compounds. However, it is its ti (C=C) coordination that opened a perspective toward a broad series of derivatized furans. It can be a bridging ligand forming (C=C)... 

Nomenclature of organometallic compounds of the transition elements (lUPAC recommendations) 99PAC1557. 

Carbene transfer reactions with participation of organometallic compounds bearing heterocyclic substituents 99CSR315. 

Grignard reagents are a very important class of organometallic compounds. For their preparation an alkyl halide or aryl halide 5 is reacted with magnesium metal. The formation of the organometallic species takes place at the metal surface by transfer of an electron from magnesium to a halide molecule, an alkyl or aryl radical species 6 respectively is formed. Whether the intermediate radical species stays adsorbed at the metal surface (the A-modelf, or desorbs into solution (the D-model), still is in debate ... 

Many metals occur in crude oils. Some of the more abundant are sodium, calcium, magnesium, aluminium, iron, vanadium, and nickel. They are present either as inorganic salts, such as sodium and magnesium chlorides, or in the form of organometallic compounds, such as those of nickel and vanadium (as in porphyrins). Calcium and magnesium can form salts or soaps with carboxylic acids. These compounds act as emulsifiers, and their presence is undesirable. 

Many other kinds of organometallic compounds can be prepared in a manner similar to that of Grignard reagents. For instance, alkyllithium reagents, RLi, can be prepared by the reaction of an alkyl halide with lithium metal. Alkyllithiums are both nucleophiles and strong bases, and their chemistry is similar in many respects to that of alkylmagnesium halides. 

Additions of organometallic compounds to 2-azelidinones such as 1 or 4 bearing a leaving group in the 4-position preferentially or exclusively afford tram-3,4-substituted /(-lactams 3 or 6. Therefore, the participation of an A -acylinline intermediate such as 2 or 5 which is attacked from the less hindered side is probable14-16. This has been exploited for the synthesis of carbapenem antibiotics, e.g., thienamycin (7)16. 

Addition of Organometallic Compounds to a,/MJnsaturated Carbonyl Compounds... 

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