Synthesis Peterson reaction

For the purpose of stereoselective synthesis the selective elimination at the stage of the /3-hydroxysilane 5 is not a problem the diastereoselective preparation of the desired /3-hydroxysilane however is generally not possible. This drawback can be circumvented by application of alternative reactions to prepare the /3-hydroxysilane 2 however these methods do not fall into the category of the Peterson reaction. 

Trialkylsilyl groups have a modest stabilizing effect on adjacent carbanions (see Part A, Section 3.4.2). Reaction of the carbanions with carbonyl compounds gives (3-hydroxyalkylsilanes. (3-Hydroxyalkylsilanes are converted to alkenes by either acid or base.270 These eliminations provide the basis for a synthesis of alkenes. The reaction is sometimes called the Peterson reaction.211 For example, the Grignard reagent derived from chloromethyltrimethylsilane adds to an aldehyde or ketone and the intermediate can be converted to a terminal alkene by acid or base.272... 

Several variations of the Peterson reaction have been developed for synthesis of alkenylsilanes.80 -P-Arylvinylsilanes can be obtained by dehydration of (3-silyloxy alkoxides formed by addition of lithiomethyl trimethylsilane to aromatic aldehydes. Specific Lewis acids have been found to be advantageous for the elimination step.81... 

T. Kawashima, R. Okazaki, Synthesis and Reactions of the Intermediates of the Wittig, Peterson, and their Related Reactions, Synlett 1996, 600. 

The Synthesis of Transient Silenes using the Principle of the Peterson Reaction... 

Synthesis and Reaction Chemistry of a,p-Unsaturated Acyl Complexes Derived from (2). Two methods for the preparation of optically active ( )- and (Z)-a,p-unsaturated iron acyls from (2) have been reported." One method involves aldol condensation of (2) with aldehydes followed by 0-methylation to produce diastereomeric acyls (18). This mixture (18) is then treated with Sodium Hydride to produce predominantly ( )-a,p-unsaturated acyl complexes (19) (eq 13). Alternatively, (2) can be depro-tonated and treated with Chlorotrimethylsilane to produce the C-silylated complex which is subsequently deprotonated and treated with an aldehyde. This Peterson alkenation produced mixtures... 

In the case of base-induced elimination, the Peterson alkenation relies on the strong bond formed between silicon and oxygen, and the ready propensity for silicon to be attacked by alkoxide, to drive the reaction. In the original study by Peterson, the -silylcarbinols were prepared by the addition of (trimethylsilyl)methylmagnesium chloride to the carbonyl. The caibinols were subsequently eliminated by treatment with sodium or potassium hydride or with sulfuric acid to form the methylene derivatives in excellent yield. The Peterson reaction has proven to be of general utility in the synthesis of alkenes. ... 

The a-silyl caibanions necessary to tqiply the Peterson reaction to higher substituted examples are limited by the ability to efficiently produce the anion. A clever example of an altenuitive to the Wittig reaction for ethylidene formation to give (285) with a-(trimethylsilyl)vinyllithium was utilized by Jung in the synthesis of coronafacic acid (Scheme 40). ... 

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 Peterson reaction, as shown in equation (70), has been applied to the synthesis of alkenes that are hindered and difficult to form by the Wittig reaction. In the case of trisubstituted alkenes (311) in which R and are components of a ring or are identical, the reaction may prove to be the method of choice. 

Kawashima, T., Okazaki, R. Synthesis and reactions of the intermediates of the Wittig, Peterson, and their related reactions. Syn/eff 1996, 600-608. 

Krempner, C., Reinke, H., Oehme, H. The synthesis of transient silenes using the principle of the Peterson reaction. Organosilicon Chemistry II From Molecules to Materials, [Muenchner Silicontage], 2nd, Munich, 1994 1996, 389-398. 

Ager, D. J. Product subclass 37 P-silyl alcohols and the Peterson reaction. Science of Synthesis 2002,4, 789-809. 

Furstner, A., Brehm, C., Cancho-Grande, Y. Stereoselective Synthesis of Enamides by a Peterson Reaction Manifold. Org. Lett 2001, 3, 3955-3957. 

We have seen that vinyl silanes can be prepared by hydrosilylation of alkynes by three different mechanisms giving good control over geometry of these inevitably terminal vinyl silanes. Vinyl silanes are stable compounds and can be isolated, unlike most of the vinyl metals we have seen so far, and other ways of making vinyl silanes allow the more-or-less controlled synthesis of mono-or trisubstituted compounds with reasonable control over selectivity. These include the Peterson reaction with two SiMe3 groups on the same carbon atom 183 and, more relevant to this chapter, reactions of vinyl lithiums with silyl chlorides.44... 

The rest of the synthesis is straightforward but you should notice the catalytic Ru(III) oxidation used both on 65 and 67, the periodate cleavage to replace ozonolysis in the formation of 68 and the Peterson reaction (chapter 15) used to make the alkene 69. This method was used for the synthesis of quantities of both enantiomers of grandisol 34. 

---