Vinyl lithium reagents

Vinylic lithium reagents (26) react with silyl peroxides to give high yields of silyl enol ethers with retention of configuration. Since the preparation of 26 from vinylic halides (12-37) also proceeds with retention, the overall procedure is a... 

The vinyl lithium reagents generated in the Shapiro reaction can be used in tandem reactions. In the reaction shown below, a hydroxymethyl group was added by formylation followed by reduction. 

An elegant approach to polyquinanes has recently been described by Paquette et aL1281 By means of an anionic-pericyclic domino reaction four new C-C bonds are formed in one process. First, a two-fold addition of a vinyl lithium reagent, e.g. cyclopentyl lithium to diisopropyl squarate takes... 

Stereocontrolled oxy-Cope rearrangement. 1,2-Addition of a chiral vinyl-lithium reagent to a chiral (3,-y-unsaturated ketone could give rise to at least eight... 

For other ways of generating vinylic lithium reagents, see page 373, Section 9, and page 379, Section 11. 

Duraisamy, M. Walborsky, H. M. Chiral vinyl-lithium reagents. Carbenoid reactions. J. Am. Chem. Soc. 1984, 306, 5035-5037. 

MFluoro-A -Z-butylbenzenesulfonamide (Table 3a, A) reacts with vinyl lithium reagents prepared from lodoalkenes to give high yields of fluoroalkenes with high stereoselectivity [84 (Thble 4)... 

Vinylic lithium reagents (43) react with silyl peroxides to give high yields of... 

Vinylic lithium reagents 107 or the corresponding 1-trihutylstannyl glycals 108 have provided useful routes to Cl-suhstituted glycals and C-glycosyl compounds [10]. The procedure has... 

In a quite different approach to LTA4 methyl ester (Scheme 3.27), Corey utilized the condensation of a 13-carbon vinyl lithium reagent with the epoxyaldehyde to generate a mixture of diastereomeric carbinols. Mesylation and elimination with base led directly to LTA4 methyl ester, apparently free of double-bond isomers. 

Functional group manipulation now gives the aldehyde 173 ready for addition to the vinyl-lithium reagent 165. The product was trapped as the MEM (methoxy-ethoxy-methyl-) derivative 174 in a very high yield but without any stereoselectivity. Fortunately, Corey already knew how to control the stereochemistry at the two OH groups by oxidation to ketones and stereoselective reduction so the synthesis could be completed. 

Alkyl-, aryl-, and vinyl-lithium reagents undergo 1,4-addition to the a/S-unsaturated imine derived from mesityl oxide. ... 

Vinyl complexes are typically prepared by the same methods used to prepare aryl complexes. Vinyl mercury compounds, like aryl mercury compoimds, are easily prepared (by the mercuration of acetylenes), and are therefore useful for the preparation of vinyl transition metal complexes by transmetallation. The use of vinyl lithium reagents has permitted the s rnthesis of homoleptic vinyl complexes by transmetallation (Equation 3.35). Reactive low-valent transition metal complexes also form vinyl complexes by the oxidative addition of vinyl halides with retention of stereochemistry about the double bond (Equation 3.36). Vinyl complexes have also been formed by the insertion of alkynes into transition metal hydride bonds (Equation 3.37), by sequential electrophilic and nucleophilic addition to alkynyl ligands (Equation 3.38), and by the addition of nucleophiles to alkyne complexes (Equation 3.39). The insertion of alkynes into transition metal alkyl complexes is presented in Chapter 9 and, when rearrangements are slower than insertion, occurs by s)m addition. In contrast, nucleophilic attack on coordinated alkynes, presented in Chapter 11, generates products from anti addition. 

Methyl enol ethers of acyl silanes have been prepared in good yield by the silyla-tion of vinyl lithium reagents derived from methyl enol ethras . Indeed, po-haps the simplest preparation of a methyl enol ether of an acyl silane results from addition of a-methoxyvinyl lithium to chlorotrimethylsilane. Acid hydrolysis gave acetyl trimethyl-silane in ca 80% yield . A similar reaction has been carried out with phenyl methyl (-butyl chlorosilane. Again, acid hydrolysis gave the acyl silane, which is of course chiral at silicon . ... 

Bond and Chamberlin have now demonstrated that t-butyl-lithium can generate the more substituted dilithio-regioisomer (54) from the trisylhydrazone (53) to give the corresponding vinyl-lithium reagent. Previous work had shown... 

A simple route to 1-methylthio- and 1-phenylthio-vinyl-lithium reagents has been described (Scheme 9). The anions have been alkylated to afford, after... 

The stereochemically controlled addition of organometallic species of copper, tin, silicon, palladium, zirconium, and boron to acetylenes has been investigated as a route to di-, tri-, and tetra-substituted olefins. The carbon-metal bond thus formed is cleaved in a stereoselective manner either directly, or indirectly, via the corresponding vinyl-lithium reagents with a wide variety of electrophiles. In three... 

Trialkylboranes may also be used to convert terminal acetylenes into trisubstituted olefins stereospecifically, via the vinyl-lithium reagent generated by Normant s procedure (Scheme 11). The stereochemistry of the product is of... 

Bond and his co-workers have demonstrated that vinyl-lithium reagents may be prepared from benzenesulphonylhydrazones. These reagents react with a variety of electrophiles providing routes to allylic alcohols, olefins, and other unsaturated functions, as outlined in Scheme 22. 

A transannular aldol reaction is also part of the squa-rate ester cascade applied by Paquette and co-workers in their expeditious 10-step synthesis of hypnophilin, an antibiotic metabolite isolated from cultures of the fungus Pleurotellus hypnophilus. Sequential 1,2-additions of a pair of vinyl lithium reagents to the squarate ester 54 led to intermediates (i.e., 56 and 58) by either trans- or... 

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