Ester enolates from

The least highly substituted amide enolate whose structure is known is the lithium enolate of N -di-methylpropionamide (170). This enolate is obtained as a dimer solvated by TriMEDA, i.e. (171). The alkene geometry in (171) is opposite that found in the ester enolates from (163) and (165). Thus in the... 

Pyrrolidone anion as EGB generates (trifluoromethyl) malonic ester enolate from malonic ester bearing a CF3 moiety at the a-position (Eq. 26). Generally, it is difficult to generate the enolate anion with a-CFg group, because the enolate anion undergoes... 

A novel method for the generation of an ester enolate from ethoxyacetylene has been developed, and its reaction with aldehydes studied (Scheme 39). The diastereoisomeric o-chloro-/3-hydroxy-esters (55) and (56) are formed in a ratio of about 2 1 in very good yield. 

Analogs of the ester enolate derived from higher carboxylic acids can also be prepared by the addition of an organometal-lic agent to methyl 2-trimethylsilylacrylate (2). The resultant ester enolate from the Michael addition can be used for a subsequent Peterson alkenation reaction when reacted with a carbonyl compound (eq 4). ... 

Lewis acid promoted condensation of silyl ketene acetals (ester enolate equiv.) with aldehydes proceeds via "open" transition state to give anti aldols starting from either E- or Z- enolates. 

The present chapter extends our study of carbanions to the enolate ions derived from esters Ester enolates are important reagents m synthetic organic chemistry The stabilized enolates derived from p keto esters are particularly useful... 

Most of the reactions of ester enolates described so far have centered on stabilized eno lates derived from 1 3 dicarbonyl compounds such as diethyl malonate and ethyl ace toacetate Although the synthetic value of these and related stabilized enolates is clear chemists have long been interested m extending the usefulness of nonstabilized enolates derived from simple esters Consider the deprotonation of an ester as represented by the acid—base reaction... 

Enolate Initiators. In principle, ester enolate anions should represent the ideal initiators for anionic polymeri2ation of alkyl methacrylates. Although general procedures have been developed for the preparation of a variety of alkaU metal enolate salts, many of these compounds are unstable except at low temperatures (67,102,103). Usehil initiating systems for acrylate polymeri2ation have been prepared from complexes of ester enolates with alkak metal alkoxides (104,105). 

Steric and stereoelectronic effects control the direction of approach of an electrophile to the enolate. Electrophiles approach from the least hindered side of the enolate. Numerous examples of such effects have been observed. In ketone and ester enolates that are exocyclic to a conformationally biased cyclohexane ring there is a slight... 

O Base abstracts an acidic alpha hydrogen atom from an ester molecule, yielding an ester enolate ion,... 

Ester enolates which contain the chiral information in the acid moiety have been widely used in alkylations (see Section D.1.1.1,3.) as well as in additions to carbon-nitrogen double bonds (sec Section D.1.4.2.). Below are examples of the reaction of this type of enolate with aldehydes720. The (Z)-enolate generated from benzyl cinnamate (benzyl 3-phenylpropcnoate) and lithium (dimethylphenylsilyl)cuprate affords the /h/-carboxylic acid on addition to acetaldehyde and subsequent hydrogenolysis, The diastereoselectivity is 90 10. 

Lower stereoselectivities arise, however, from the addition of ester enolates to this glyceralde-hyde4. Another highly stereoselective addition is in the synthesis of erythromycin A where a single product results from the addition of lithiated tert-butyl thiopropanoate to the enantiomerically pure aldehyde (2/ ,3/ ,4,S, 6/ ,7/ ,8,S, 9/ ,10.S, 11 / )-7-acetoxy-3,4 9,10-bis(isopropy1-idenedioxy)-11-methoxymethoxy-2,4,6,8,10-pentamethyltridecanal5. 

We might have recognised this as a Claisen-Cope product since it is a y > < -unsaturaLed ester. Disconnecting and inverting the allylic group from the ester enolate gives the start ing material 32), Ortho esters are usually used as the reagents. 

Geranyl chloride can be prepared from geraniol by the careful use of triphenylphosphine in carbon tetrachloride. Tris(dimethylamino)phosphine reacts with carbon tetrachloride to form the complex (42) which can be used to form the enol esters (43) from acid anhydrides. Similarly, aldehydes form the alkenes (44), and esters or amides of trichloroacetic acid are converted to glycidic esters. ... 

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