Gilman cuprate

Since the preformed aggregate Bu3Cu2Li showed a diastereoselectivity of 83 17 in the presence of boron trifluoride16, the low diastereoselectivity noted above was presumably due to a faster addition reaction of butyllithium, which is formed by the treatment of the Gilman cuprate with the boron trifluoride-diethyl ether complex16,, s. 

Representative procedure forthecouplingofan alkenyliodonium tosylate with a Gilman cuprate ( )-(2-bromoprop-1 -enyl)benzene [64] To a stirred suspension of Cp2Zr(H)Cl (0.360 g, 1.4 mmol) in THF (6 mL) was added phenyl(phenylethynyl)iodonium tosylate (0.476 g,... 

Initial attempts to perform the 1,5-substitution enantioselectively with chiral enyne acetates proceeded disappointingly. For example, treatment of the enantio-merically pure substrate 51 with the cyano-Gilman cuprate tBu2CuLi LiCN at -90 °C provided vinylallene 52 as a 1 3 mixture of E and Z isomers with 20 and 74% ee, respectively (Scheme 2.19) [28], As previously described for the corresponding Sn2 substitution of propargylic electrophiles, this unsatisfactory stereoselection may be attributed to a racemization of the allene by the cuprate or other organome-... 

The discovery of the Gilman cuprate Me2CuLi [5-8], and House s [6, 7] and Corey s [8] demonstrations of its synthetic potential, produced a major breakthrough in this area of chemistry. A major disadvantage of the application of this type of cuprate reagents in stoichiometric amounts, especially from the point of view of atom economy , is the fact that one equivalent of the (potentially valuable) organic component is usually not used in the reaction and ends up as chemical... 

The solution structures of cyano-Gilman cuprates and lower-order cyanocuprates have been studied by cryoscopic measurements in THF [141]. The results of this study have in several cases shown ways to obtain useful single crystals of several higher- and lower-order cyanocuprates and consequently to determine their structures in the solid state. It appears that a number of these cyanocuprates retain their observed solid-state structure when dissolved in THF. 

A drawback of the Z enoates is usually lower reactivity, reflected in prolonged reaction times and higher reaction temperatures. This may be overcome by switching to more reactive enone systems. Thus, addition of the functionalized cyano-Gilman cuprate system 67 to Z enone 66 proceeded smoothly at low temperatures, with excellent acyclic stereocontrol at the /i-stereocenter [26, 27]. Stereocontrol upon... 

An interesting chromium system example is represented by complex 145. Addition of cyano-Gilman cuprates occurred with complete diastereoselectivity to give conjugate adducts 146 (Scheme 6.28). Interestingly, the opposite diastereomer was accessible by treatment of enone 145 with a titanium tetrachloride/Grignard reagent combination [71c]. 

Scheme 6.41. Stereoselective construction of a quaternary stereocenter by allylic substitution of mesylate 195 with a boron trifluoride-modified cyano-Gilman cuprate reagent.

In the 1952 paper mentioned above [3], Gilman reported on the formation of lithium dimethylcuprate from polymeric methylcopper and methyllithium. These so-called Gilman cuprates were later used for substitution reactions on both saturated [6] and unsaturated [7, 8, 9] substrates. The first example of a cuprate substitution on an allylic acetate (allylic ester) was reported in 1969 [8], while Schlosser reported the corresponding copper-catalyzed reaction between an allylic acetate and a Grignard reagent (Eq. 2) a few years later [10]. 

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