Organo aluminum reagents

Yamamoto reported an asymmetric hetero-Diels-Alder reaction that was catalyzed by a chiral organo-aluminum reagent (300).244 when diene 299 reacted with benzaldehyde in the presence of 10 mol% of 300, a mixture of ci -dihydropyrone (301) and rran -dihydropyrone (302) was obtained in 77 and 7% yield, respectively. The optical activity of(301 was 95% ee, and that of 302 was 53% ee. 44 jf, ( g complex that mediates this reaction, the diene approaches benzaldehyde with an endo alignment that minimizes steric repulsion between the incoming diene and the front triphenylsilyl moiety. 

SELECTIVE ACTIVATION OF CARBONYL COMPOUNDS USING ORGANO-ALUMINUM REAGENT... 

Zirconium-aluminum analogs of the Tebbe reagent have been reported to react with carbonyl compounds slowly, in low yield or not at all. However, zirconium aUcylidenes which are stabilized by a phosphorus rather than an aluminum ligand do transfer their alkylidene moiety to carbonyl. These results provide some of the few examples of long chain alkylidene transfer to ca nyl from an organo-metallic reagent (equation 31). 

The reaction of allyl organometallics (8) with achiral aldimines (9) is the simplest combination of reactants, stereochemically, and affords (except in the case of formaldehyde imines) homoallylamines (10) containing one stereocenter (equation 2). These reactions, which typify the general scope of allyl organo-metallic-imine reactions are surveyed in Table 2. Reactions of allyl-borane, -titanium and -aluminum reagents are not shown in Table 2, only because they have been reported in reactions with chiral imines and are discussed in Sections 4.3.2.1.2 and 4.3.2.2. 

C-Addition to carbon-carbon double bonds CC U CC Addition-halogenation 16 576 Adenosine triphosphate as reactant 18 151 Adipic acid as reagent 18 232 Adiponitrile as reagent 17 577 20 302 Air s. Oxygen Alanes (s. a. Aluminum compounds, organo-)... 

When an atom center is complexed with a metal, that atom will have some characteristics of an anion and can often behave as a nucleophile. An organo-metallic Grignard reagent (RMgBr) is an example of such a nucleophile that often behaves as if it were a carbanion. It is convenient to draw a Grignard reagent as a carbanion, but since it is not truly an ionic species, quotation marks are typically drawn around the carbanion when it is used in a mechanism ( Rr ). This same convention is sometimes used for the nucleophilic hydride species ( Hr ) that is available when using lithium aluminum hydride (LiAlHt). 

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