Vinylic cuprates

This reaction illustrates a stereoselective preparation of (Z)-vinylic cuprates, which are very useful synthetic intermediates. They react with a variety of electrophiles such as carbon dioxide, epoxides, aldehydes, allylic halides, alkyl halides, and acetylenic halides they undergo... 

In a lolal syntliesis of cdc25.A ptolein phosphatase inbibdot dysidiolide i46) [37], substilulion on an sp- carbon center by vinyl cuprate was used lo accom-... 

Vinyl cuprates.17 Vinyl cuprates can be prepared conveniently by in situ trans-metallation of vinylstannanes, available by hydrostannylation of alkynes, with a cuprate such as (CH3)2Cu(CN)Li2 (equation I). Reagents prepared in this way effect conjugate addition of the vinyl group to an enone with essentially no transfer of the methyl group. 

The initial reports in 1982-83 by Westmijze et. al. [25a] and Piers [25b] on the addition of stannylcopper and cuprate reagents to simple alkynes were followed by full studies [76] and reports from several laboratories [14b, 16b-e, 25c, 77-78]. In the earlier studies, the vinylcopper species could only be trapped with a proton. Marino achieved success in the addition to cyclohexenone of the vinyl cuprate generated by addition of BusSnCuCNLi to acetylene [79a-b], and Fleming [79c]... 

The formed vinylic cuprates readily perform conjugate addition to a,)3-unsaturated carbonyl compounds giving 8-vinyl-substituted ketones. 

Vinyl stannaries5 are versatile synthetic intermediates. They serve as a source of stereospecific vinyl anions and vinyl cuprates. a, dIn the presence of Pd(0), vinylstannanes can be acylated7a,b or alkylated, 7c, d Epoxidation followed by rearrangement converts vinylstannanes into carbonyl... 

Corey and Fuchs (39) noted the vinyl cuprate addition on J15 to produce 116 stereospecifically. Clark and Heathcock (40) observed the lithium dime-thylcopper addition on 117 which yielded 118 while Trost, Taber, and Alper (41) reported the conversion of 119 into 120 with the same reagent. 

First an iodination of the alcohol is accomplished by treatment with iodine in presence of Ph3P and imidazole.13 Successive iodide displacement with the nucleophilic vinyl cuprate derived from 2-lithiopropene (2-bromopropene, tBuLi) finished the emplacement of the C-l side chain. Cleavage of the TPS ether by tetrabutylammonium fluoride and subsequent oxidation with the Dess-Martin periodinane provides aldehyde 9. 

The above-described problem demonstrates the first enantioselective synthesis of dysidiolide, a C25 isoprenoid antimitotic agent. The central transformations are the sulfenylation-dehydrosulfenylation sequence to prepare an a,/5-tnone, the biomimetic cationic 1,2-rearrangement to form stereoselectively the bicyclic scaffold, vinyl cuprate displacement of an iodide furnishing the C-l side chain and the photochemical oxidation of furan to generate the j hydroxy-butenolide functionality. 

Conjugate addition of vinyl cuprate and dimethyl malonate to 4,4-dimethylcyclo-hexa-2,5-dienones has allowed facile access to mono- and bis-adducts in good yields. Whereas the high diastereoselectivity to afford trans-bis-adducts was predictable,... 

Vinyl cuprates.3 An attractive route to vinyl cuprates involves transmetalla-tion of vinylzirconates, available by hydrozirconation of 1-alkynes with the Schwartz reagent in THF at 25°. Transmetallation can be effected with CH3Li (3 equiv.)... 

The stannylcupration of alkynes has been widely studied. Reaction of alkynes with lithium bis(tributylstannyl) cuprate leads to r -2-(tri butyl stannyl) vinyl cuprates, which are synthetically equivalent to cis- 1,2-ethylene dianions. Addition of the tin-copper reagent across the triple bond occurs i>7/-stereospecifically, thus providing Z-vinylstannanes. Phenylacetylene reacts with the tin cuprate with a regiochemistry opposite to that of 1-decyne.294 The intermediate cuprates react well with the various electrophiles.295 For example, the reaction with ethylene oxide gives primary alcohols, and further treatment of their />-toluenesulfonates with butyllithium gives 1-substituted cyclobutenes (Equation (120)) 294... 

An aryl halide with an alkyl or vinyl cuprate. 

This reaction illustrates a stereoselective preparation of (Z)-vinylic cuprates, 5 which are very useful synthetic Intermediates. They react with a variety of electrophiles such as carbon dioxide,5,6 epoxides,5,6 aldehydes,6 allylic halides,7 alkyl halides,7 and acetylenic halides 7 they undergo conjugate addition to a,6-unsaturated esters,5 6 ketones,6 aldehydes,6 and sulfones.8 Finally they add smoothly to activated triple bonds6 such as HCSC-OEt, HC3C-SEt, HC=C-CH(0Et)2. In most cases these cuprates transfer both alkenyl groups. The uses and applications of the carbocupration reaction have been reviewed recently.9 The configurational purity in the final product 1s at least 99.951 Z in the above transformations. 

Ethyl acrylate will react with vinylic cuprates, but at a much slower rate than a, -unsaturated ketones and ethyl propynoates 205). Complex-ation with trimethyl phosphite is advantageous because the reactivities of the cuprate and resulting carbanion are increased. Glutarate esters are important by-products from the reaction of the intermediate carbanion with another molecule of the acrylate the primary addition product was obtained in yields from 3.4% to 38% and the glutarate ester in 7.1-31% yield. 

Lithium divinyl cuprates.5 The addition of vinylic cuprates to chiral y-alkoxy-a,P-unsaturated ketones and esters proceeds with high diastereoselectivity the major product is that in which the vinyl group is anti to the ally lie alkoxyl group. The geometry of the unsaturated system does not affect the stereochemistry of the addition. 

---