Peterson alkenation cerium

The use of cerium trichloride for the Peterson alkenation has been q)plied by Ueda and cowoikers for nucleoside synthesis (Scheme S2). The anion was generated with LDA/cerium trichloride and condensed with the aldehyde (375). The product was treated with KH in THF and the pyrimidopyridine (377) isolated in S0% yield. 

See Section 3.1.10 for substituted examples of the cerium Peterson alkenation. 

Peterson Alkenation. Trimethylsilylmethyllithium (1) provides an alternative to a Wittig approach for the preparation of methylene compounds from carbonyl precursors. In some cases the use of (1) is superior to the Wittig approach. Condensation of (1) with a carbonyl compound results in the formation of a 8-hydroxysilane. Elimination to the alkene can be acconqtlished by use of acidic or basic conditions (eq 1). acetyl chloride or thionyl chloride can also be used to accomplish this elimination. A wide variety of aldehydes and ketones have been used as substrates in this reaction. The use of cerium(III) chloride has been advocated with reagent (1) to favor nucleophilic addition with enolizable carbonyl corrqtounds. The use of the lithium agent (1) gives superior yields compared to the use of trimethylsilylmethyl-magnesium chloride with cerium, ... 

Reaction with Carboxylic Acid Derivatives. Reaction of (1) with carboxylic acid derivatives provides silyl ketones (3) (eq 4). The reaction 3ueld is very dependent upon the presence of a-hydrogens in the substrate lower yields are obtained when deprotonation can occur at this center. The reaction occurs with esters, lactones, acid chlorides, and the parent carboxylic acids. The resultant /3-silyl ketones can be desilylated by simple hydrolysis, or used as a substrate in a Peterson alkenation approach to enones. The use of a cerium reagent with the acid chloride has been advocated for the preparation of allylsilanes. ... 

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