Enolate anions, nitro compounds, reaction with

Because non-basic substances may also produce a similar reaction, it was later suggested by Anslow and King [66] that the enolate anion of creatinine forms a coordinate bond with the positively charged nitrogen atom of one of the nitro groups. The structure of the compound they postulated is VII ... 

Ambident anions are mesomeric, nucleophilic anions which have at least two reactive centers with a substantial fraction of the negative charge distributed over these cen-ters ) ). Such ambident anions are capable of forming two types of products in nucleophilic substitution reactions with electrophilic reactants . Examples of this kind of anion are the enolates of 1,3-dicarbonyl compounds, phenolate, cyanide, thiocyanide, and nitrite ions, the anions of nitro compounds, oximes, amides, the anions of heterocyclic aromatic compounds e.g. pyrrole, hydroxypyridines, hydroxypyrimidines) and others cf. Fig. 5-17. 

Aliphatic nitro compounds show a number of reactions which parallel those of carbonyl chemistry. Primary and secondary nitro compounds exhibit tautomerism paralleling keto-enol tautomerism (Scheme 3.94a). Aliphatic nitro compounds dissolve in aqueous sodium hydroxide with the formation of sodium salts. The resultant anions behave as carban-ions and will condense with aldehydes. An example involves the formation of m-nitrostyrene from nitromethane and benzaldehyde (Scheme 3.94b). 

In many of these cases, both the enolate anion and substrate can exist as (Z) or (E) isomers. With enolates derived from ketones or carboxylic esters. The (E) enolates gave the syn pair of enantiomers (p. 166), while (Z) enolates gave the anti pair. Nitro compounds add to conjugated ketones in the presence of a dipeptide and a piperazine. ° Malonate derivatives also add to conjugated ketones, and keto esters add to conjugated esters.Addition of chiral additives to the reaction, such as metal-salen complexes,proline derivatives, or (—)-sparteine, ... 

NaBHj/NiC or Raney nickel, the menthyloxy group is removed with NaBH /KOH to give 3,4-disubstituted butyrolactones with a high diastereo- and enantioselectivity (Figure 7.69). Corey and Houpis [1458] have described asymmetric Michael reactions of ketone enolates with a 2-thiophenyl crotonate of 8-phenmenthol. Chirality has also been introduced on the amino group of 2-ami-nomethyiacrylates to perform the asymmetric addition of the anion of the tert-Bu ester of cyclopentanecarboxylate [1459], More important developments have been reported with chiral a,p-unsaturated sulfoxides and nitro compounds as Michael acceptors (see below). 

Treatment of ll,ll-dichloro-l,6-methano[10]annulene with Bu"Li in an ether solvent yields C22H hydrocarbons of labile and complex nature/ Trapping experiments support the intermediacy of compounds ( )6) and (607) formed by the sequence of rearrangements (605)- (606)- (607). Reaction of cyclo-octa-2,4,6-trien-l-one with the anion of methyl 4-(dimethylphosphinyl)but-2-enoate gave (608) and (609) the predominant isomer (609) resulted from base-catalysed isomerization of (608) under the conditions of reaction. Low-temperature oxygenation of the enolate anion derived from the mixture of (608) and (609), followed by reduction with triethyl phosphite, gave a 1 1 mixture of 8-methoxycarbonylbicyclo[5,3,l]undeca-l,3,5,9-tetraen-8-exo-ol and -1,3,5,8-tetraen-lO-exo-ol. Pyrolysis of the p-nitro-benzoate esters of these alcohols effected their conversion into methyl 1,5-methano-[10]annulenecarboxylate (610). 

There has been a major review of substitution by the radical-chain 5rn1 mechanism. It has been shown that reaction by the SrnI pathway of the enolate anions of 2- and 3-acetyl-l-methylpyrrole may yield a-substituted acetylpyrroles. The dichotomy of reactions of halonitrobenzenes with nucleophiles has been nicely summarized major pathways include reduction via radical pathways and. SnAt substitution of halogen. EPR spectroscopy has been used to detect radical species produced in the reactions of some aromatic nitro compounds with nucleophiles however, whether these species are on the substitution pathway is questionable. The reaction of some 4-substimted N,N-dimethylanilines with secondary anilines occurs on activation by thallium triacetate to yield diphenylamine derivatives radical cation intermediates are proposed. ... 

A new synthesis of aldehydes with 2-methyl-2-thiazoline has the advantage of releasing the aldehydes from the thiazolidine intermediate under neutral conditions . Acetylene derivatives can be obtained from aldehydes via dibromomethylene compounds Novel reactions of alkynes with cationoid electrophiles have been published. -Diketones and 2-ketoalkoximes can be obtained by this reaction from acid chlorides and aliphatic nitro compounds respectively Addition of aldehydes to activated carbon-carbon double bonds occurs smoothly in the presence of cyanide ions as catalysts . Poly- -carbonyl compounds have been prepared by condensation of two anions, whereby the enolate salt of a y8-keto ester condenses as an electrophilic anion with strong nucleophiles such as the dianion of benzoylacetone. ... 

Selenenyl halides are relatively stable, though moisture sensitive, compounds that are generally prepared by the reactions shown in Scheme 7 and behave as electrophilic selenium species. They react with ketones and aldehydes via their enols or enolates to afford a-seleno derivatives (e.g. (17) in equation 11). Similar a-selenenylations of /3-dicarbonyl compounds, esters, and lactones can be performed, although the latter two types of compounds require prior formation of their enolates. Moreover, the a-selenenylation of anions stabilized by nitrile, nitro, sulfone, or various types of phosphorus substituents has also been reported (equation 12). In many such cases, the selenenylation step is followed by oxidation to the selenoxide and spontaneous syn elimination to provide a convenient method for the preparation of the corresponding Q ,/3-unsaturated compound (e.g. 18 in equation 11). Enones react with benzeneselenenyl chloride (PhSeCl) and pyridine to afford a-phenylselenoenones (equation 13). 

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