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

Abstract

Abstract:It is shown that the N-(p-ethoxyphenyl) group on β-lactams can be oxidatively removed by ceric ammonium nitrate in good yield. Fourteen new N-(p-ethoxyphenyl)-2-azetidinones 8a-n were synthesized through standard [2+2] ketene-imine cycloadditions (Staudinger reaction). Treatment of these compounds with ceric ammonium nitrate yielded the N-dearylated 2-azetidinones 9a-n in good to excellent yields. The effects of solvent, molar equiv of CAN and different temperatures have been investigated and optimum conditions were established.

Cerium(iv) ammonium nitrate mediated 5-endo-dig cyclization of α-amino allenylphosphonates to spirodienones

“…These results led us to propose the following mechanism: in the first step the para-methoxybenzyl ring is oxidized to the cyclohexadienone carbocation 9. 35 Next, a 5-endo-dig cyclization leads to the formation of the iminium ion 10. The nucleophilic addition of water to the latter followed by a prototropy transforms the phosphonate moiety as a leaving group leading to the lactam 3 and diethyl phosphite which is instantly degraded by the excess of CAN (Scheme 3).…”

Divergent, stereoselective access to heterocyclic α,α-quaternary- and β2,3,3-amino acid derivatives from a N-Pmp-protected Orn-derived β-lactam

“…Among the described methods for the temporal protection of β-lactam-NH, some electron-rich phenyl moieties are within the most profusely exploited. [27][28][29] These moieties, exemplified by the N-p-methoxyphenyl group (Pmp), can easily be removed by ceric ammonium nitrate (CAN) under relatively mild conditions. [30][31][32] In addition, this oxidative cleavage is highly compatible with a large number of functional groups, making this protection/deprotection procedure a good option for our purposes.…”

One-step Synthesis of β-lactams Using Cyanuric Fluoride

“…Spectral data for 4a-f and 4h-j have been previously reported. 14,16,20,27,28 Synthesis of 2-azetidinones (4a-m); general procedure Cyanuric fluoride (1.5 mmol) was added to a solution of substituted acetic acids (1.5 mmol), imines (1.0 mmol) and triethylamine (5.0 mmol) in dry CH 2 Cl 2 (20 mL) at room temperature and the mixture was stirred overnight. The reaction mixture was washed successively with saturated NaHCO 3 (20 mL) and brine (10 mL).…”

“…[8][9][10][11][12] Commonly, ketenes are prepared in situ by reaction of acyl halides with tertiary amines. [13][14][15] However, the application of acyl halides for the preparation of ketenes has some disadvantages such as low availability, instability and difficulty of preparation. To solve these problems, acid activators have been used for the one-pot synthesis of 2-azetidinones from imines and carboxylic acids.…”