Alkylzinc chloride reagents

Table 3.5 Reactions of alkylzinc chloride reagents with benzoyl chloride.

E)-(2-Bromoethenyl)dibromoborane, BrCH==CHBBr2, can be used in place of 1 to couple alkylzinc chlorides with an alkyl chloride to form a monoene, but this reagent is unsatisfactory for coupling of alkenylzinc chlorides.1... 

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],... 

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],... 

This must reflect activation of the carbonyl group by magnesium ion, since ketones are less reactive to pure dialkylzinc reagents and tend to react by reduction rather than addition.141 The addition of alkylzinc reagents is also promoted by trimethylsilyl chloride, which leads to isolation of silyl ethers of the alcohol products.142... 

Lewis acids catalyze the reaction of alkylzinc reagents with acyl chlorides.160 The reaction is also catalyzed by transition metals, as is discussed in Chapter 8. 

Kataoka et al. showed that vanadium(m) or (rv) chloride, upon reaction with 1 equiv. of an alkylzinc reagent, generates an alkylvanadium species in situ which reacts with aldehydes or ketones at 0 °C to give the corresponding secondary or... 

Zinc was effectively activated from zinc chloride using lithium and a catalytic amount (10%) of naphthalene in order to prepare secondary or tertiary alkylzinc bromides 517 (starting from the corresponding aUcyl bromides 516). These reagents react with acyl chlorides or a,/3-unsaturated ketones to give the expected ketones 15 and 518 (Scheme 143). 

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

Cross-coupling of RMgX with organic halides (9, 147). This complex is the most active and selective known catalyst for coupling of n- and sec-butylmagnesium chloride or the corresponding alkylzinc reagents with aryl and vinyl bromides.1... 

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