Deprotonation, Peterson olefination

Despite the paucity of data for 9 itself, there now exists a wide range of derivatives in the cyclopropabenzene and -[Z ]naphthalene series that have been expanded upon since a 1987 accountThe preparation of these derivatives can be effected by one of three distinct routes depending upon the particular nature of the compound sought. Each has its limitations and none has provided a parent methylenecycloproparene. The first method depends upon the availability of the cycloproparenyl anion (Section IV.B) which can be intercepted by trimethylsilyl chloride to give silane 93 (R=H). In turn, deprotonation of 93 at the benzylic position affords the stabilized a-silyl anion that gives alkylidene derivatives 94 (R=H) from interaction with an appropriate carbonyl compound in a Peterson olefination (Scheme 12). The reaction sequence can be effected as a one-pot operation... 

In the first step 21 is deprotonated with LDA to form lithium trimethylsilyldiazomethane (35), which attacks aldehyde 34 to give 36. Then 38 results via 37 by Peterson olefination under basic conditions. Next, 38 loses N2 to form carbene 39, which rearranges finally to the alkyne 40. Alkyne 22 was used without further purification in the next steps. 

The Peterson olefination may also be applied to the preparation of a,P-unsatu-rated esters, thus providing an attractive alternative to the HWE phosphonate method. For example, deprotonation of trimethylsilylacetate with RjNLi followed by addition of cyclohexanone yields the intermediate P-hydroxysilane, which, on elimination of the silicon-oxygen moieties, furnishes ethyl cyclohexylidene-acetate. ... 

The Peterson olefination is known for its better performance compared to the corresponding Wittig process for hindered substrates. This is demonstrated in the first asymmetric synthesis of (+)-maritimol, a member of the stemodane diterpenoids (eq 66). Thus, the key step, a Thorpe-Ziegler annulation, requires a 1,5-dinitrile motif. This is achieved by the generation of an a-silyl boronate, obtained by BuLi deprotonation of trimethylsilylace-tonitrile and subsequent transmetalation with triisopropyl borate, which is then condensed with the tricyclic aldehyde. ... 

Anionic pentacoordinated 1,2-oxagermetanide was synthesized quantitatively by deprotonation of the corresponding -hydroxygermane (Scheme 10)63. Upon heating at 150 °C for 30 days, this compound equilibrated with another diastereoisomer and underwent a Peterson-type reaction with elimination of olefins (Scheme 10). 

Ketones are rarely used as electrophiles in the enantioselective aldolization while they find application to enantioselective olefination reactions such as the Horner-Wadsworth-Emmons or the Peterson reaction. For instance, the deprotonation of an achiral phos-phonoacetate by a set of chiral 2-aminoalkoxides led to the corresponding enolate that... 

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