Transmetallation Butyllithium

Tosylation (see also Sulfonylation) /7-Toluenesulfonyl chloride, 313 Transesterification f-Butyldimethylsilyl trifluoromethanesul-fonate, 50 Butyllithium, 56 Transetherification Bromodimethylborane, 47 Transmetallation Butyllithium, 319... 

Stannane 6a underwent facile transmetalation in tetrahydrofuran at — 78 °C on treatment with butyllithium to afford 6b. Addition of the lithium reagent 6b to a solution of 1.1 equivalents of copper(I) bromide-dimethyl sulfide in 1 1 diisopropyl sulfide/tetrahydrofuran at — 78 °C gave the copper reagent 6c, which reacted with methyl vinyl ketone at —78 "C in the presence of boron trifluoride-diethyl ether65, producing 7 in 55% yield65. 

A copper-mediated cyclization of metallated thiophenes has been utilized to prepare polycyclic thiophenes and thiophene cyclophanes. Treatment of dibromide 106 in succession with M-butyllithium (halogen-metal exchange), zinc chloride (transmetallation), and copper chloride gave 7//-cyclopcnta[ 1,2-fc 4,3-6 dithiophene (107) <00H(52)761>. This conversion has also been achieved using a palladium-mediated cyclization performed in the presence of hexamethylditin . Copper-mediated cyclizations have also been applied to the syntheses of cyclopenta[2,l-6 3,4-A ]dithiophen-4-one (108) (three steps from 73) <00S1253> and cyclophane 109 <00CC2329>. 

The addition of carbonyl compounds towards lithiated 1-siloxy-substituted allenes does not proceed in the manner described above for alkoxyallenes. Tius and co-work-ers found that treatment of 1-siloxy-substituted allene 67 with tert-butyllithium and subsequent addition of aldehydes or ketones led to the formation of ,/i-unsaturated acyl silanes 70 (Scheme 8.19) [66]. This simple and convenient method starts with the usual lithiation of allene 67 at C-l but is followed by a migration of the silyl group from oxygen to C-l, thus forming the lithium enolate 69, which finally adds to the carbonyl species. Transmetalation of the lithiated intermediate 69 to the corresponding zinc enolate provided better access to acylsilanes derived from enolizable aldehydes. For reactions of 69 with ketones, transmetalation to a magnesium species seems to afford optimal results. 

In the case of symmetrical divinyl tellurides, the displacement of both vinyl groups is achieved by employing 2 equiv of n-butyllithium. Aryl vinyl tellurides give a mixture of products, since both Ar-Te and vinyl-Te bonds are transmetallated on reaction with n-BuLi, leading to vinyl- and aryllithiums. The butyl vinyl tellurides give only the desired vinyl-lithiums. The reactions are stereospecific with retention of the C=C bond geometry. °... 

When the protocol is applied to allylcarbamates 170, the deprotonation in the presence of (—)-sparteine does not occur with kinetic preference. Indeed, a dynamic resolntion by crystallization takes place. The epimeric allylfithinm componnds 171 and 172 are eqni-librating, whereby one of them crystallizes predominantly. Under optimized conditions, when n-butyllithium is used for the deprotonation and cyclohexane serves as a cosolvent, the preference of the diastereomer 172 leads to snbstimtion products in 90-94% gg393-395 enantioselective homoaldol reaction has been developed based on this protocol Transmetalation of the organolithium into the titaninm compound occnrring nnder inversion of the configuration (172 173) and subseqnent addition to aldehydes leads to... 

In regard to this latter point, Cubbon and Margerison noted (31) that adding n-butyllithium to toluene led to the formation of solutions which "developed a yellow-orange color.") If the spectrum of benzyllithium in toluene in the presence of anisole resembles that in benzene where the X max is reported (32,33) to be 292 nm, the decay in absorbance with time noted (13) at 330 nm may be attributable to transmetallation involving toluene rather them the foregoing aromatic ethers. 

Bromo-l-lithiocyclopropanes, readily obtained by transmetalation of 1,1-dibromocyclo-propanes with butyllithium in tetrahydrofuran at — 100 CC, undergo addition to aldehydes and ketones forming bromohydrins. On warming, before workup, the adducts from ketones (but not from aldehydes) eliminate lithium bromide and cyclizc to oxaspiropentanes, which may be rearranged to cyclobutanones by treatment with acids (Table 6).76-78... 

The reagent (1) can be generated conveniently in situ by transmetallation of (trimethylsilylmethyl)tri-M-butyltin with n-butyllithium in THF/hexane at 0° (equation... 

Tributylstannylmagnesium chloride and tributylstannylalkalis reacted with iminonium salts to form non-substituted, a-substituted or a,a-disubstituted aminomethyltributyltins. Transmetallation of the aminomethyltributyl tins with butyllithium followed by condensation with carbonyls provided a regiospecific route to / -aminoalcohols (Scheme 51)87. 

Iron-catalyzed Suzuki-Miyaura coupling reactions were also reported by Nakamura and colleagues (entry 27) [67]. Alkyl halides 1 and mixed pinacol aryl(butyl)borates, generated in situ from arylboronates and butyllithium, were used as the reagents and 10 mol% of the iron complexes 16a or 16b as the catalysts. The addition of 20 mol% of MgBr2 was essential for the success of the reaction. Products 3 were isolated in 65-99% yield. The methodology tolerates ester and nitrile functions. The reaction starts probably by initial boron-iron transmetalation to generate a diaryliron(II) complex. 

Corriu and coworkers found that the reaction of (Z)-y-Af,lV-bis(trhnethylsilyl)amino-1-propenylstannane 298 with butyllithium, followed by quenching with methyl iodide and then hydrolysis, provided 3-methylamino-l-propenylsilane 299 in high yield (equation 185)446, suggesting an anionic 1,4-silyl migration from N to C in the (Z)-vinyllithium 300 to give 301 (equation 186). The transmetallation of the ( )-isomer of 298 gave no silyl migration products (equation 187)447. 

Zirconocene dichloride reacts with butyllithium and hex-3-yne at —78 °C in THF to give almost quantitatively red l,l-bis(cyclopentadienyl)-2,3,4,5-tetraethyl-l-zirconacyclopenta-2,4-diene 60. Transmetallation with antimony trichloride yields the corresponding l-chloro-2,3,4,5-tetraethyl-l-stibole (Scheme 9) <20000M2393>. 

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