Nucleophiles organometallic

Stereoselective Michael additions of organocopper reagents to the trans-crotonyl ester of the chiral auxiliary 10-sulphonamido-isonorborneol generates, after hydrolysis, B-substituted carboxylic 

3-Alky 1-2,3-epoxy-acids undergo epoxide ring opening with 

Stereoselective reactions of acyl ligands attached to the iron 

In the presence of Et2AlCl the lithium enolate derived from the iron acetyl complex [(C H )Fe(CO)(PPh )C0Me] discriminates between 

Tricarbony1- -methyItetrahydroisoquinolinechromium undergoes stereo- and regio-selective 4-exo-deprotonation and subsequent electrophilie additions to generate the corresponding 4-exo-deriva-tives which after decomplexation yield 4-alkyl-, 4-phenyl-, and 4- 

FIGURE 17.63 1,2-Addition of a Grignard reagent to an unsaturated aldehyde. 

FIGURE 17.64 Conjugate addition of a Grignard reagentto an unsaturated carbonyl compound in 

FIGURE 17.65 Mechanisms for addition of organocopper reagents to enones. 

FIGURE 17.66 Conjugate addition of organocopper reagents in synthesis. 

The mechanisms given simply use a carbanion as nucleophile in terms of identifying the product, this will serve. 

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Organometallic nucleophilic reagents change the reaction pattern drastically. 

Organometallic nucleophile Reaction conditions Yield of 73a + 73b (%) Ratio 73a 73b... 

The nature of the organometallic nucleophile in equation 1 can be quite diverse and even highly functionalized, leading to a variety of differently substituted sulfoxides. For examples, the sulfoxides have been prepared in enantiomerically pure form by... 

Mejorado investigated the asymmetric addition of various organometallic nucleophiles using method A, but the reaction could not be catalyzed. The intermediates proved to be far too reactive. However, he established that the addition of a stoichiometric amount of a preformed chiral complex [an admixture of Taddol (r/om-a, -(dimethyl-1,3-dioxolane-4,5-diyl)bis(diphenyl methanol)) and EtMgBr] to 5 affords some enantiomeric excess in the resulting phenol product 6 (Fig. 4.12).13... 

Payne rearrangement. The Payne rearrangement2 of a primary cts-2,3-epoxy alcohol to a secondary 1,2-epoxy alcohol usually requires a basic aqueous medium, but it can be effected with BuLi in THF, particularly when catalyzed by lithium salts. As a consequence, the rearrangement becomes a useful extension of the Sharpless epoxidation, with both epoxides available for nucleophilic substitutions. Thus the more reactive rearranged epoxide can be trapped in situ by various organometallic nucleophiles. Cuprates of the type RCu(CN)Li are particularly effective for this purpose, and provide syn-diols (3).3... 

Asymmetric microbial oxidation afforded the (-)-epoxide which has been explored as a building block ring opening reactions with organometallic nucleophiles, and via Friedel-Crafts reactions have been reported. [226,227]. A non-biotransformative approach to this epoxide has also been described [228]. Copper(II)-catalysed oxidative hydrolysis (Eq. 72) affords a lactic acid analogue in high enantiomeric purity [229]. 

Since the anion N is a nonstabilized carbanion, an organometallic nucleophile such as an organolitliium or a Grignard reagent could be prepared from the corresponding bromide. 

In a search for open-chain 1,3-stereo-control, addition of organometallic nucleophiles [MeLi, MeMgBr, Me3ZnLi, Me2CuCNLi2, (PhMe2Si)2CuLi, etc.] to a series of (5-... 

The choice of the organometallic nucleophile (Zn, B, or Si) has been shown to facilitate the straightforward conversion of enone (195) into the opposite diastereoisomers g) of 2-substituted pyrrolizidinones (196)/(197) via the rhodium-catalysed 1,4-addition reaction.244... 

Prim, D. Campagne, J.-M. Joseph, D. Andrioletti, B. Palladium-catalyzed reactions of aryl halides with soft, non-organometallic nucleophiles. Tetrahedron 2002, 58, 2041-2075. 

Organometallic nucleophiles and free radicals offer complementary functional group compatibility, such that a proper selection of the reactive intermediate could allow for the presence of a desired spectator functional group needed for later elaboration to synthetic targets of interest. Seeking to demonstrate this potential for improved versatility, we initiated a program to develop a variety of radical addition reactions of imino compounds [24]. In the process, we introduced new modes of... 

If conjugate addition of an organometallic nucleophile is desired, this can be accomplished by using a lithium diorganocuprate reagent, which has the organic group at-... 

OH 1 Section 18.6 Reaction with organometallic nucleophiles (Grignard... 

The reaction stops at stage I if the original Nu has only one unshared pair of electrons (CN- hydrides, organometallic nucleophiles). 

As usual, the best strategy is to identify the nucleophile and the electrophile. This chapter introduced a new electrophile, the carbonyl carbon of an aldehyde or ketone. The nucleophiles are listed in Table 18.2. Hydride, water, HCN, and organometallic nucleophiles result in the addition of the nucleophile to the carbon and a hydrogen to the oxygen of the carbonyl group. Ylides and nitrogen nucleophiles result in the formation of a double bond between the carbonyl carbon and the nucleophile. And alcohols and thiols add two nucleophiles to the carbonyl carbon. 

First, the general mechanisms for these reactions are presented. Then the reactivity of these carboxylic acid derivatives is discussed. As expected, the factors that control the reactivity are very similar to those that affect the addition reactions of Chapter 18. Next, reactions with nucleophiles that interconvert all of the members of the carboxylic acid family are presented. Finally, the reactions of hydride and organometallic nucleophiles with these electrophiles are discussed. 

By using the reactions described in Sections 19.2 through 19.6, it is possible to convert one carboxylic acid derivative to any other carboxylic acid derivative. Now let s examine the reactions of these compounds with hydride and organometallic nucleophiles. In these cases the products are no longer carboxylic acid derivatives. 

O The organometallic nucleophile attacks the carbonyl carbon and displaces the pi electrons onto the oxygen. 

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