Organocuprates example preparation

Organocuprates. The preparation of cuprates from organozincs is viable due to the tolerance of many functional groups (e.g., esters) in the reagents. There are also more synthetic pathways to the organozincs for example, from an alkene it is possible to achieve hydroboration and boron-zinc exchange. 

There has been a great deal of study concerning the effect of solvents and other reaction conditions on the stability and reactivity of organocuprate species.8 These studies have found, for example, that (CH3)2S-CuBr, a readily prepared and purified complex of CuBr, is an especially reliable source of Cu(I) for cuprate preparation.9 Copper(I) cyanide and iodide are also generally effective and, in some cases, preferable.10... 

Conjugate addition of organocuprates has seen many applications in complex synthesis. For example, in the preparation of an opiate alkaloid it was necessary to introduce a methyl group at a late stage of the synthesis.110 The transformation of (47) to (48) was successfully carried out with Me2CuLi in a stereoselective manner (equation 51). 

The chemistry of iron vinylidene complexes is dominated by the electrophilicity of the carbon atom adjacent to the iron organometallic unit. While addition of water leads to an acyl complex (i.e., the reverse of the dehydration shown in equation 10), addition of an alcohol leads to a vinyl ether complex. Similarly, other iron vinyl complexes can be prepared by the addition of thiolate, hydride, or an organocuprate (Scheme 33). " The nucleophilic addition of imines gave enaminoiron intermediates that could be further elaborated into cyclic aminocarbenes. This methodology has been used to provide access to /3-lactams and ultimately penicillin analogs, and good diastereoselectivities were observed (6 1-15 1) (Scheme 34). 04 Iso, vinylidene complexes are intermediates in cyclizations of alkynyl irons with substituted ketenes, acid chlorides, and related electrophiles an example is shown (equation 11). These cyclizations led to the formation of a series of isolable and characterizable cyclic vinyl iron complexes. 

Reaction with propioiactone. The reaction of organocuprates with / -propio-lactone can be used to prepare -substituted propionic acids.7-8 Examples ... 

Additional examples of the applicability of organocuprates to the preparation of C-glycosides were reported by Bellosta, et al.25 His work, shown in Scheme 2.3.3, illustrated the selective formation of both a and p anomers... 

Coupling reactions with alkyl halides often use large excess of cuprate, as mentioned above, which can be a severe limitation if the halide precursor to the organocuprate is difficult to prepare or unavailable from commercial sources. A solution to this problem is to prepare a cuprate with a ligand that is less reactive, allowing selective transfer of the substituent of choice. An example is the use of 417 in a reaction with 418 that... 

The reaction is not limited to the use of simple organocuprates very complex cuprates can be prepared and then reacted with complex carbonyl partners, leading to products with very sophisticated structures. Mixed cuprate 417 was one example. Another example that used an unsymmetrical organocuprate is Sih s reaction of... 

This is a very general reaction in that primary, secondary, and tertiary alkyl halides react with primary, secondary, or tertiary organocuprates. The halide can be a chloride, a bromide, or an iodide, but iodides are more reactive than bromides, which are more reactive than chlorides. Another example is the reaction of 49 with lithium diphenylcuprate to give 50. The reaction of alkyl halides and organocuprates is the preferred method for coupling an alkyl halide to an organometallic compound. Many different hydrocarbons can be prepared. 

In addition to the ate complexes prepared from 2 equiv of RLi, the organocopper(I) conpounds RCu, prepared from 1 equiv of RLi and CuL have found synthetic application in the presence of additives, which enhance the reactivity of these otherwise relatively unreactive compounds. Both Lewis bases and Lewis acids " have been used for this purpose, and their utility has been extended to the organocuprates as well. Examples of the former are phosphines, such as tri-butylphosphine, and sulfides, such as dibutyl sulfide and dimethyl sulfide examples of the... 

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