Anodic N-dearylation of 2-azetidinones

Solid‐Solid Phase and Solvent‐Free Oxidative Removal ofN‐(4‐Alkoxyphenyl) Groups of Monocyclic β‐Lactams with Ceric Ammonium Nitrate as a Cheap, Simple, and Efficient Method

“…The change of the color was a good indicator of its formation. The presence of water is necessary, and the reported mechanism [18] confirms it. After 15 min, the mortar was fully colored.…”

A Chiral, Oxidatively Cleavable Auxiliary in β-Lactam Synthesis - Double Diastereocontrol with p-Methoxyphenethyl-Substituted Imines

“…Several methods for the cleavage of the PMPE-group in 7b were tested: While oxidation with Nbromosuccinimide 14 led to decomposition of the substrate, no reaction was observed with triphenylcarbenium tetrafluoroborate, 15 m-chloroperbenzoic acid (mCPBA), 16 or dimethyldioxirane (prepared in situ from oxone/acetone) 17 or under electrolytical conditions. 18 Oxidation with ammonium peroxodisulfate/silver nitrate (catalytic amount) 19 gave the deprotected b-lactam product, but due to the formation of a side product, whose identity could not be solved, the yields were unsatisfactory (46%). Since no over-oxidation (vide supra) is possible with the PMPE group, even stronger oxidising agents can be used.…”

Synthesis of Novel N-(4-Ethoxyphenyl) Azetidin-2-ones and Their Oxidative N-Deprotection by Ceric Ammonium Nitrate

“…Cycloaddition reactions of imines 7a-f with phthalimidioacetyl chloride and phenoxyacetyl chloride in the presence of triethylamine (Method A) or of imines 7a-b with 2-naphthoxyacetic acid, 2,4-dichlorophenoxyacetic acid and methoxyacetic acid in the presence of p-toluenesulfonyl chloride and triethylamine (Method B) gave cis/trans 2-azetidinones 8a-k and 8l-n, respectively, in good to excellent yields (Scheme 2, Table 1). The mechanism of the ketene-imine cycloaddition reaction involves initial nucleophilic attack of the imine nitrogen on the ketene carbonyl to form a zwitterionic intermediate, which cyclizes to form the β-lactam [21].…”

“…The lower yield of N-unsubstituted β-lactams in aqueous acetonitrile at -10 o C may be attributed to the low solubility of 2-azetidinones 8a-n at that temperature. According to a reported mechanism for the cleavage of p-methoxyphenyl group [21], following mechanism shown in Scheme 4 is suggested for the oxidative cleavage of p-ethoxyphenyl moiety. …”