The Tin-Peterson Reaction

The synthesis of simple terminal alkenes has been reported by the reaction of (triphenylstannyl)methyllithium with carbonyl compounds [390]. (Phenylthio)-triphenylstannylmethyllithium and benzaldehyde can be selectively transformed into ( )-yS-(phenylthio)styrene or, alternatively, its Z-isomer via yS-hydroxyalkyl-stannane 241 by means of a tin-Peterson reaction (Scheme 2.148) [391]. LDA is usually used as the base in the tin-Peterson reaction. Butyllithium is not a suitable base for abstraction of the a-proton because lithium-tin exchange may occur [259]. 

Scheme 2.148. The tin-Peterson reaction of an a-stannyl carbanion with benzaidehyde.

Scheme 2.151. The Peterson reaction and the tin-Peterson reaction of a-stannyl carbanions bearing another group 14 element moiety.

This reaction has been modified by the use of an a-silyl selenoacetamide to generate -olefins in preference and the use of an a-silyl thioether and A-cyclohexyl-(2-triethylsilylpropylidene)imine as of-silyl carbanion precursors. In addition, a germanium-Peterson reaction" and a tin-Peterson reaction" have been developed. Furthermore, an asymmetric version of the Peterson olefination has been developed by the use of an external chiral tridentate amino diether as a chiral ligand. ... 

The Germanium, Tin, and Lead Versions of the Peterson Reaction 2.5.5.1 The Cermanium-Peterson Reaction... 

The Peterson reaction has two more advantages over the Wittig reaction 1. it is sometimes less vulnerable to sterical hindrance, and 2. groups, which are susceptible to nucleophilic substitution, are not attacked by silylated carbanions. The introduction of a methylene group into a sterically hindered ketone (R.K. Boeckman, Jr., 1973) and the syntheses of olefins with sulfur, selenium, silicon, or tin substituents (D. Seebach, 1973 B.T. Grdbel, 1974, 1977) illustrate useful applications. The reaction is, however, more limited and time consuming than the Wittig reaction, since metallated silicon derivatives are difficult to synthesize and their reactions are rarely stereoselective (T.H. Chan, 1974 ... 

As a general mle, unless an anion-stabilizing group, such as phenyl, or a heteroatom such as sulfur is present, the alkylsilane is not readily deprotonated. The a-halosilane can be deprotonated but, unlike the readily available chloromethyltrimethylsilane, there are few general methods to this approach. Al-kyllithium reagents add to vinylsilanes ( ) to produce the carbanion (287). Silyl derivatives with heteroatoms, such as sulfur, selenium, silicon or tin, in the a-position (288) may be transmetallated (Scheme 41). Besides the difficulty in synthesizing the anion, alkene formation lacks specificity for simple di- and tri-alkyl-substituted alkenes. As a result, the Peterson reaction of an a-silyl carbanion with a carbonyl has found the greatest utility in the synthesis of methylene derivatives, (as discussed in Section 3.1.3), heterosubstituted alkenes and a,p-unsaturated esters, aldehydes and nitriles. 

The compound BusSnCHMeCHMeOH shows anti-elimination up to 100 °C, but. yyn-climination above 100 °C, when the reaction occurs through the compound Bu3SnCHMeCHMeOSnBu3 which is formed by reaction with the bis-tributyltin oxide which is eliminated.95 The intermediate 6-1 in the base-induced Un-Peterson elimination of a p-hydroxyalkyltin compound has been isolated as a stable compound. X-Ray crystallography shows that the configuration at the tin is closer to a square pyramid than a trigonal bipyramid.96 97... 

Four-membered heterocyclic systems have been postulated to be involved as intermediates along the reaction pathway in a number of systems allowing olefin synthesis. This is the case of the Wittig reaction (phosphorus) and a family of related reactions the boron-Wittig (boron), the Peterson (silicon) 44 and the Peterson-type reactions (germanium, tin, lead). 5,l46 11 these systems,... 

Lead-Peterson olefination is achieved similarly to the germanium and tin versions, though the lead version is not advantageous over the latter reactions in most cases. A much simpler and more gentle elimination method applicable to the lead compounds is to pass the solution of the bis(triphenylplumbyl)ethanol derivative 249, which is synthesized from triplumbylmethane 248 and benzaldehyde, through a silica gel column (Scheme 2.152) [399]. 

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