Ketones dimetallations

The 1,1-dimetallic compounds, R2C(SnMe3)ZnBr, were oxidized by dry air at —10 to 0°C in the presence of Me3SiCl to give aldehydes or ketones, R2C=0. In a related indirect method, arylthallium bis(trifluoroacetates) (prepared by 12-21) can be converted to phenols by treatment with lead tetraacetate followed by triphenylphosphine, and then dilute NaOH. Diarylthallium trifluoroacetates undergo the same reaction. ... 

In another one-pot process, Nakamura has developed a novel synthesis of pyrroles through the [3+2] coupling of a ketone hydrazone 5 and a vinyistannane <99OL1505>. In this procedure, zincated hydrazone 6 is converted to the gem-Zn/Sn dimetallic intermediate 7 which upon exposure to oxygen directly affords the l-(dimethylamino)pyrroles 8. 

Diastereoselective metallo-Claisen reactions can be used to prepare aldol-type products if the 1,1-dimetallic reagents 91 obtained are oxidized to aldehydes or ketones (equation 43)37f. 

The reactivity of the dimetallic compounds 186a and 186b was then investigated and these species were less reactive than their formulas would lead to predict, as no reaction occurred with ketones, esters, Michael acceptors or trimethylsilyl chloride. In the presence of BF3 OEt2, addition occurred to aldehydes and led after /3-elimination to the corresponding olefination products 189 with good to excellent (E) stereoselectivity (equation 92)127. 

Substituted gem-dimetallic compounds, readily obtained via allylation of alkenyl organometallics, react with aldehydes in the presence of BF3-Et20 but do not react with ketones. When alkylidenemalonates are used instead of aldehydes, the Z-olefins see (E) (Z) Isomers) are obtained with a very high stereoselectivity (Scheme 35). A transmetallation reaction with copper cyanide significantly increases the reactivity of gm-dimetallic derivatives via formation of 1,1-zinca cyanocuprates. Indeed, when these compounds react with... 

The a-chloro-a-sultinyl ketone 20 was prepared from methyl benzoate and chloromethyl phenyl sulfoxide 19 after in situ a-lithiation. Compound 20 is dimetallated by KH and f-BuLi to give the keto dianion 21, which is converted into a potassium/lithium ynolate 22 (equation 7). The resulting metal ynolates are converted into thioesters, carboxylic acids, amides and esters (Section V). 

The 1,1-dimetallic compounds R2C(SnMe3)ZnBr were oxidized by dry air at -10 to 0°C in the presence of MeaSiCl to give aldehydes or ketones R2C=0. ... 

Enaminones 93 can be regioselectively dimetallated to give the kinetic dianion 94 or the thermodynamic dianion 95. Treatment of 94 and 95 with epoxides 96 gives isomeric hydroxy enaminones 97 and 98, which cy-clize under acidic conditions to give a-tetrahydrofurylidene ketones 99 [92JCS(P1)2095]. (See Scheme 27 on facing page.)... 

Thermolysis of the complex when R = Et yields the first d (p,3-alkylidyne) complex, [Cp Ti(p.-0)]3( i3-CMe). Reaction of [CpTi(SCH2CH2CH2S](Cl)] with MeLi or AlMe3 gives the dimetallic complex, 14. This complex readily inserts ketones or imines into the highly strained thiatitana cyclopropane ring. 5... 

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