Cerium(IV) Tetrabutylammonium Nitrate (CTAN): A Mild and Efficient N-dearylation Agent for Synthesis of N-unsubstituted 2-azetidinones
作者:Maaroof Zarei
DOI:10.3184/174751917x14902201357392
日期:2017.4
A simple and efficient protocol for the conversion of N-p-methoxyphenyl, N-p-ethoxyphenyl, N-p-methoxynaphthyl, N-3,4-dimethoxybenzyl and N-p-methoxybenzyl-2-azetidinones to N-unsubstituted 2-azetidinones using cerium(IV) tetrabutylammonium nitrate (CTAN) in dichloromethane is described. The method is compatible with a number of functional groups, and N-unsubstituted 2-azetidinones can be prepared
Solid‐Solid Phase and Solvent‐Free Oxidative Removal of<i>N</i>‐(4‐Alkoxyphenyl) Groups of Monocyclic β‐Lactams with Ceric Ammonium Nitrate as a Cheap, Simple, and Efficient Method
作者:Aliasghar Jarrahpour、M. Zarei
DOI:10.1080/00397910801981326
日期:2008.5
Five N-(4-methoxyphenyl)- and five N-(4-ethoxyphenyl)-beta-lactams were prepared by ketene-imine [2+2] cycloaddition (Staudinger reaction). Then these 2-azetidinones were N-dearylated by grinding together with ceric ammonium nitrate without hazardous solvents in good to excellent yields. The solid-solid phase N-dearylation is easier, simpler, and more efficient than the general method in solution. The pure N-unsubstituted beta-lactams obtained by a nontedious workup and without further purification.
Enantioselective hydrolysis of 3,4-disubstituted β-lactams. An efficient enzymatic method for the preparation of a key Taxol side-chain intermediate
作者:Zsolt Galla、Ferenc Beke、Enikő Forró、Ferenc Fülöp
DOI:10.1016/j.molcatb.2015.11.011
日期:2016.1
3,4-Disubstituted beta-lactams 3-benzyloxy-4-(4-chlorophenyl)azetidin-2-one [(3S*,4R*)-(+/-)-1], 3-benzyloxy-4-phenylazetidin-2-one [(3S*,4R*)-(+/-)-2] and 4-(4-chlorophenyl)-3-phenoxyazetidin-2-one [(3S*,4R*)-(+/-)-3] were resolved through immobilized CAL-B-catalysed ring-cleavage reactions. Excellent enantioselectivities (E>200) were obtained for (3S*,4R*)-(+/-)-1 and (3S*,4R*)-(+/-)-2 when the reactions were performed with added H2O as nucleophile in tert-butyl methyl ether at 70 degrees C, whereas only moderate E (12) was achieved for (3S*,4R*)-(+/-)-3 under the same conditions but in diisopropyl ether. The resulting ring-opened beta-amino acids [(2R,3S)-4 (ee>98%), (2R,3S)-5 (ee > 98%) and (2R,3S)-6 (ee = 50%)] and the unreacted beta-lactams [(3S,4R)-1-3] (ee > 98%) could be easily separated. (C) 2015 Elsevier B.V. All rights reserved.