Alkylzinc reagents preparation

Ketones can be prepared by trapping (transmetallation) the acyl palladium intermediate 402 with organometallic reagents. The allylic chloride 400 is car-bonylated to give the mixed diallylic ketone 403 in the presence of allyltri-butylstannane (401) in moderate yields[256]. Alkenyl- and arylstannanes are also used for ketone synthesis from allylic chlorides[257,258]. Total syntheses of dendrolasin (404)f258] and manoalide[259] have been carried out employing this reaction. Similarly, formation of the ketone 406 takes place with the alkylzinc reagent 405[260],... 

The preparation and the use of several C2-symmetric disulfonamides derived from 1,2-amino alcohols in the Ti-catalysed enantioselective addition of di-alkylzinc reagents to aldehydes was described by Yus et al., in 2002. The best... 

Configurational integrity of secondary alkylzinc reagents had been demonstrated by Knochel although the preparation of the zinc reagent was not practical (Scheme 8.8) [13],... 

Scheme 6.16. Zr-catalyzed enantioselective addition of alkylzinc reagents to imines utilizes peptidic ligands and can be used to prepare a variety of aromatic amines in high optical purity.

The hydroboration of dienic silyl enol ethers, such as 124, with LItBH leads to organob-oranes which can be converted to new diorganozincs, such as 125 (Scheme 42) . More importantly, this method allows the preparation of chiral secondary alkylzinc reagents. 

Mangeney and coworkers have found that alkylzinc reagents add to reactive imine derivatives and have used this property to prepare chiral amino acids (Scheme 94). The... 

Huo, S. Highly efficient, general procedure for the preparation of alkylzinc reagents from unactivated alkyl bromides and chlorides. Org. Lett. 2003, 5, 423 125. 

The hydroboration of allylic amine or alcohol derivatives can be used for the preparation of alkylzinc reagents with excellent diastereoselectivity (Equation (34)). Rhodium-catalyzed hydroborations are also compatible... 

Other examples of this series include a selection of ate complexes prepared by the treatment of alkylzinc reagents with freshly distilled alkaline earth metals under extrusion of elemental zinc. This route was employed to prepare a strontium zincate in which the alkaline earth metal center adopts a distorted octahedral geometry completed by two THF solvent donors. Similar reactions with barium metal lead to structurally closely related compounds. Flexibility in solvent choice is noted by the preparation of related complexes in toluene, displaying metal-toluene itt-interactions. 

Regio- and stereoselective synthesis of tri- and tetrasubstituted alkenes by introduction of CO2 and alkylzinc reagents into alkynes in preparation of natural products 07EJO4981. 

Pd-catalyzed coupling of acyl halides with organometallic reagents is a useful synthetic method of ketones. The alkylzinc reagent 127, prepared from the corresponding alkyl iodide with Zn/Cu couple, was coupled with the acid chloride 128 to give the ketone 129 in 50 % yield and used for the total synthesis of amphidinolide T14 [55]. 

A facile and convenient preparative method of alkylzinc reagents is direct reaction of alkyl iodides with activated Zn/Cu couple [47] or Zn dust [48]. Huo reported an efficient, general preparative method of alkylzincs from unactivated... 

Total synthesis of (+)-pumiliotoxin A (39) has been achieved based on the Negishi coupling of the alkylzinc chloride 37, derived from the alkyl iodide, with the alkenyl iodide 38 at room temperature, and subsequent deprotection [58], The alkylzinc reagent 41 was prepared conveniently by the reaction of the alkyl iodide 40 with Zn/Cu couple, and treated with 2-iodoimidazole 42 to afford the adduct 43 [47],... 

The alkyl nucleophiles used in the reactions shown in Eq. (5.26) and Figure 5.12 are all prepared from primary alkyl halides. Similar reactions with secondary alkylzinc reagents are more difficult, not only because of the increased steric hindrance but also because of the possibility for a secondary metal-alkyl species to undergo isomerization. For the coupling of propargyUc electrophiles specifically. 

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