Lactams enolates

A chiral sulfoxide can be used as a leaving group for the asymmetric inducdon via addidon-eliminadonprocess. 5-Lactam enolates are converted into the corresponding nitroalkenes subsdnited with lactams fEq. 4.101. ... 

When 2-lithio-2-(trimethylsilyl)-l,3-dithiane,9 formed by deprotonation of 9 with an alkyllithium base, is combined with iodide 8, the desired carbon-carbon bond forming reaction takes place smoothly and gives intermediate 7 in 70-80% yield (Scheme 2). Treatment of 7 with lithium diisopropylamide (LDA) results in the formation of a lactam enolate which is subsequently employed in an intermolecular aldol condensation with acetaldehyde (6). The union of intermediates 6 and 7 in this manner provides a 1 1 mixture of diastereomeric trans aldol adducts 16 and 17, epimeric at C-8, in 97 % total yield. Although stereochemical assignments could be made for both aldol isomers, the development of an alternative, more stereoselective route for the synthesis of the desired aldol adduct (16) was pursued. Thus, enolization of /Mactam 7 with LDA, as before, followed by acylation of the lactam enolate carbon atom with A-acetylimidazole, provides intermediate 18 in 82% yield. Alternatively, intermediate 18 could be prepared in 88% yield, through oxidation of the 1 1 mixture of diastereomeric aldol adducts 16 and 17 with trifluoroacetic anhydride (TFAA) in... 

A deprotonation-alkylation sequence from tetrahydro-oxazolo[3,4- ]pyridin-5-ones or hexahydro-oxazolo[3,4-r ]pyridin-3-ones is an especially efficient method for diastereoselective functionalization, respectively, via the lactam enolate or... 

Since the trapping of the lactam enolate with electrophiles should not be limited to nitroolefins, extension to conjugate additions to alkenylsulfones, the ring opening of N-tosylaziridines, alkylation with functionalized halides, and silylation with chlorotrimethylsilane were explored. 

The cycloaddition of the /V-2-methoxvphenvI aldimines with lithium ynolates (for a review see [134]) has been reported to give (3-lactams enolates, that... 

Table 4 Dehydrogenation of Ketone, Ester, Lactone and Lactam Enolates ...

MoOPH (Section 2.3.2.1.2.ii) may be a suitable reagent for lactam enolate hydroxylation. This is suggested by the oxidation of lactam (148). Cleariy the label enolate is not strictly applicable to the bridgehead carbanion and it is likely that more forcing conditions would be necessary for genuine enolate hydroxylations. It is not clear whether V-oxidation would then emerge as a source of problems. 

Hydroxylation of amide and lactam enolates using Davis reagents (Section 2.3.2.1.2.iii) occurs readily at low temperature. The process can be highly stereoselective and is viaUe for oxidation of both sec-... 

The reaction of (41) with electron-deficient imines yields 2-azetidinones resulting from a 1 2 addition (Scheme 45). The total stereoselectivity of the reaction has been explained on the basis of steric approach control and chelation in transition state (43). The intermediate p-lactam enolate (42) is more nucleophilic than the starting ynolate. This unfavorable nucleophilicity ratio is responsible for the formation of a 1 2 adduct. This represents a severe limitation of the reaction as a generd route toward P-lactams. 

It has been demonstrated that the reaction of a lactam enolate with diethyl phosphoro-chloridate and subsequent oxidation is an equally attractive method for transformation of different N-farnesyl lactams and imides (307) to the corresponding a-phosphono lactams (308) (Scheme... 

Miscellaneous Azides. Ethyl (A-methanesulfonyl)azidoformimidate [N3C (0Et)=NS02Me] has been used to aminate chiral cyclopentanone enamines but the yields are low and the reaction could not be extended to the corresponding cyclohexanone enamines.303 Trimethylsilyl azide (TMSN3) transfers the TMS rather than the azide group to a lactam enolate.339... 

Diphenylphosphinoyl)hydroxylamine (Eq. 137),143 azo esters (Eq. 138),460 and arenesulfonyl azides (Eq. 139)339 have been used to aminate lactam enolates. In the azidation of the lactam 70,461 the diazo compound 73 predominates over azide 72 even though trisyl azide is used as the animating agent amination with di(ferf-butyl) azodicarboxylate was unsuccessful. The closely related lactam 71462 reacts normally with trisyl azide (Eq. 140). 

Several groups have studied aldol reactions of simpler 3-lactam enolates. Diarylazetidinones such as... 

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