Organocuprates coupling reactions

Problem 26.3 Synthesize each product from the given starting materials using an organocuprate coupling reaction, a. —CH2CH2CH(CH3)2 -----------------------> <( —Br + (CH3)2CHCH2CH2l... 

Scheme 8.1 gives several examples of the use of coupling reactions of organocuprate reagents with halides and acetates. Entries 1 to 3 are examples of the... 

Alkanes can also be prepared from alkyl halides by reduction, directly with Zn and acetic acid (AcOH) (see Section 5.7.14) or via the Grignard reagent formation followed by hydrolytic work-up (see Section 5.7.15). The coupling reaction of alkyl halides with Gilman reagent (R 2CuLi, lithium organocuprates) also produces alkanes (see Section 5.5.2). 

The synthetic potential of coupling reactions between vinyliodonium salts and organocuprates has not been exploited. However, some indication of their promise is provided by reported syntheses of bicyclic enediynes in the norbornadiene and 7-oxanor-bornadiene series from the appropriate bisiodonium triflates and lithium dialkynyl-cuprates (equation 221)148. 

Copper-catalyzed cross-couplings between unactivated alkyl halides and organomagne-sium compounds have been known since the late 1960s and probably are the most studied alkyl-alkyl coupling reactions. The main drawback of this protocol was the need of stoichiometric amounts of copper salts for the formation of the organocuprate, and consequently this led to loss of 1 equiv. of the non-transferred alkyl group. 

In this concluding section, we will recall that a-selanylvinylmetal derivatives can be produced by a-deprotonation of vinylic aryl selenides 11, cleavage of ketene selenoacetals 12 or bromine/lithium exchange of a-bromovinyl selenides 13 (Scheme 49). These strategies involve vinylic selenides whose syntheses are not simple. More recent works have used organocuprate additions, hydrometala-tions (M = Sn, Zr) or hydroborations of readily available acetylenic selenides 14 (Scheme 49). The process can be regio- and stereocontrolled and produce the a-selanylvinylmetal derivatives under mild conditions. The latter can be considered as vinyl dianion equivalents and are very useful intermediates for cross-coupling reactions. 

What steps are needed to convert 1 -butene (CH3CH2CH = CHg) to octane [CH3(CH2)6CH3] using a coupling reaction with an organocuprate reagent Aii carbon atoms in octane must come from 1-butene. 

Inconsistent with both of the above mechanistic proposals is the recent finding that secondary iodides, unlike bromides and sulfonates, undergo nearly complete racemization in coupling reactions with organocuprates. In addition, bicyclic compounds are produced in reactions of 6-iodocyclooctene with... 

The first organometallic compounds used in coupling reactions were Gilman reagents, also called organocuprates. They are prepared by the reaction of an organolithium reagent with cuprous iodide in diethyl ether or THF. 

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