Lactams, enolates, reaction with halides

These compounds can be alkylated twice at the 6-position in a stereocontrolled fashion (eq 2). Treatment of the unsubstimted bicyclic lactam with Lithium Diisopropylamide and reaction of the enolate anion with an alkyl halide affords the monosubstimted product The epimeric mixture is treated again with LDA and a second alkyl halide to give the dialkylated bicyclic lactam. The... 

The sulfenylation of esters,lactones, carboxylic acids,amides and lactams may be effected by reaction of the corresponding lithium enolates in THF at -78 to 0 C with dimethyl or diphenyl disulfides, or, less commonly, with methyl or phenyl sulfenyl halides. The enolates of ketones, however, are insufficiently nucleophilic to react wiA dialkyl sulfides unless HMPA is added to the reaction mixture, although they do react smoothly with diaryl sulfides. This difference allows the selective sulfenylation of esters in the presence of ketones (entry 5, Table 3). ... 

Cinchona alkaloids such as 121 possess a nucleophilic quinuclidine structure and can act as versatile Lewis bases to react with ketenes generated in situ from acyl halides in the presence of an add scavenger. By acting as nucleophiles, the resulting ketene enolates can react intermolecularly [53] or intramolecularly [54] with electrophilic C=0 or C=N bonds to deliver formal [2 + 2]-cycloadducts, such as chiral P-lactones or [1-lactams, via aldol (or Mannich)-i intramolecular cydization sequence reactions (Scheme 8.46). The nucleophilic ammonium enolate can also read with energetic... 

The common methods for the S5mthesis of p-lactams are cycloaddition reactions such as the Staudinger s ketene-imine cycloadditions, ester enolate-imine cycloadditions, alkyne-nitrone cycloadditions (Kinugasa reaction), alkene-isocyanate cycloadditions, and Torii s cyclocarbonylation of allyl halides with imines. Several cyclizahon reactions of p-amino esters, p-amino acids, p-hydroxamate esters, and a-diazocarbonyls have been developed for the formation of p-lactam ring. N,N-Disubstituted a-haloamides cyclize by C3-C4 bond formation leading to the formation of P-lactam ring. 

---