With organocuprates

Scheme 2.27 Ibuka s ring-opening reaction of (5-aziridinyl-a,(S-enoates with organocuprates.

Scheme 2.28 Wipfs ring-opening reaction of (3-aziridinyl-a, 3-enoates with organocuprates.

Treatment of cyclic vinylaziridine 105 with organocuprates of the R2CuLi type proceeds in a highly syn-selective manner (Scheme 2.29) [46], The syn stereochemistry of the reaction reflects the effect of the acetonide group, which directs the nucleophilic attack to the less hindered a-face. The formation of SN2 products 109 from the cyclic (chlorovinyl)aziridine 107 can be explained by assuming a syn-SN2 ... 

Remarkable y-syn-substitution preference is observed in the reaction of allylic carbamates with organocuprates. 

Reactions of Primary and Secondary J osylates with Organocuprates... 

Benzenesulfomc acid, 4-methyl, 2,2 dimeth ylpropyl ester [1-Propanol, 2,2-di-methyh, p-toluenesulfonate], 55, 112 Benzenesulfomc acid, 4-methyl-, esters [p-Toluenesulfonates], reaction with organocuprates, 55, 112 Benzenesultonic acid, 4-methyl-, ( )-4-hexen-l-yl ester ]( )-4-Hexen-l-yl p-toluenesulfonate], 55, 57 Benzenesulfomc acid, 4-methyl-, 1-methyl-heptyl ester [2-Octanol, p-toluenesulfonate], 55,112... 

Reaction of Alkyl Halides and Sulfonate Esters With Organocuprates... 

Propiolaldehyde diethyl acetal has found numerous synthetic applications in the literature which may be briefly summarized. The compound has been utilized in the synthesis of unsaturated and polyunsaturated acetals and aldehydes by alkylation of metal-lated derivatives, " by Cadiot-Chodkiewicz coupling with halo acetylenes, " and by reaction with organocuprates. Syntheses of heterocyclic compounds including pyrazoles, isoxazoles, triazoles, and pyrimidines have employed this three-carbon building block. Propiolaldehyde diethyl acetal has also been put to use in the synthesis of such natural products as polyacetylenes " and steroids. ... 

Hydroxy stannanes can be prepared by cleavage of epoxides with BusSnLi or cleavage of epoxy stannanes with organocuprates (equation 33)72. The two methods are stere-ochemically complementary. The higher order cyanocuprate, Bu3Sn(Bu)Cu(CN)Li2, also affords /1-hydroxy stannanes by reaction with epoxides54. 

When treated with organocuprates, 2,3-epoxy alcohols can be converted to substituted 1,3-diols with high regioselectivity and stereoselectivity. Thus, as... 

Chiral -hydroxy esters.1 Optically pure (3,7-epoxy esters (2), obtained as shown from chiral 3-hydroxybutyrolactones (1, available from malic acid), react with organocuprates to form optically pure (3-hydroxy esters. 

Scheme 2.3 Formation of pharmacologically active target molecules by Sn2 substitution of propargylic electrophiles with organocuprates.

The reaction of 1,2-allenyl ketones with organocuprates afforded /3,y-unsaturated enones. The reaction with mixed cuprates RR CuLi delivered, depending on the properties of R and R, two products 430 and 431 [192]. 

As in the case of addition reactions of carbon nucleophiles to activated dienes (Section HA), organocopper compounds are the reagents of choice for regio- and stereoselective Michael additions to acceptor-substituted enynes. Substrates bearing an acceptor-substituted triple bond besides one or more conjugated double bonds react with organocuprates under 1,4-addition exclusively (equation 51)138-140 1,6-addition reactions which would provide allenes after electrophilic capture were not observed (cf. Section IV). 

Only few examples have been reported so far on nucleophilic addition reactions to acceptor-substituted polyenes123,124,186 188. In 1933, Farmer and Martin186 examined the reaction of methyl 2,4,6-octatrienoate with sodium dimethyl malonate and isolated the 1,4-adduct as major product (equation 81). In contrast to this, 3,5,7-nonatrien-2-one and ethyl 2,4,6-octatrienoate react with organocuprates under 1,8-addition to provide the 4,6-dien-2-ones and 3,5-dienoates, respectively (equation 82)187. 

It was already noted that activated enynes bearing an acceptor substituent at the double bond react with organocuprates under 1,6-addition to provide functionalized allenes (see Section III.A)38. Interestingly, the preference of these reagents for triple bonds persists even when the distance between the acceptor group and the triple bond is increased by the introduction of further double bonds. For example, lithium dimethylcuprate attacked ethyl 8,8-dimethyl-2,4-nonadien-6-ynoate at the triple bond exclusively, and regioselective... 

Scheme 6.32. Different stereochemical results with mesylate (156) and carbamate (158) leaving groups upon allylic substitution with organocuprates.

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