Facile stereoselective synthesis of cis- and trans-3-alkoxyazetidin-2-ones
作者:Aman Bhalla、Paloth Venugopalan、Shamsher S. Bari
DOI:10.1016/j.tet.2006.06.062
日期:2006.8
A highly stereoselectivesynthesis of cis- and trans-3-alkoxy-3-phenyl/benzylthioazetidin-2-ones is described. The reaction of α-chlorosulfide-β-lactams with various alcohols catalyzed by a Lewis acid such as ZnCl2 in the presence of molecular sieves (3–4 Å) leads to cis-3-alkoxy-3-phenyl/benzylthio-β-lactams whereas treatment of potassium 2-alkoxy-2-phenylthioethanoate with appropriate Schiff's base
A new synthetic approach for spiro-β-lactams by cyclization of cis-3-allyl-3-benzylthio-β-lactams is presented. The reaction involves step-wise electrophilic addition-dealkylation sequence giving stereospecific synthesis of C-3-spiro-β-lactams.
An Unusual Lewis Acid Promoted Isomerization of trans-3-Halo-3-phenylthio-b-lactams
作者:Shamsher S. Bari、Paloth Venugopalan、Renu Arora、Garima Modi、Sachin Madan
DOI:10.3987/com-04-10299
日期:——
A method for C-3 epimerization of 3-halo-3-phenylthio-β-lactams, mediated by Lewisacids, is described. TiCl 4 promotesisomerization of trans-3-chloro-3-phenylthioazetidin-2-ones (2) to cis-3-chloro-3-phenylthioazetidin-2-ones (3). TiBr 4 promotesisomerization as well as substitution of chlorine with bromine affording isomeric cis- and trans-3-bromo-3-phenylthioazetidin-2-ones (5) and (6) respectively
C-3 β-lactam carbocation equivalents: versatile synthons for C-3 substituted β-lactams
作者:Aman Bhalla、Sachin Madan、Paloth Venugopalan、Shamsher S. Bari
DOI:10.1016/j.tet.2006.03.050
日期:2006.5
An efficient and operationally simple strategy for the synthesis of differently C-3 monosubstitutcd (9) and disubstituted (10) monocyclic beta-lactams is described. This involves reaction of beta-lactam carbocation equivalents (8) with an active aromatic, aliphatic and heterocyclic substrates in the presence of a Lewis acid. (c) 2006 Elsevier Ltd. All rights reserved.
A facile Lewis acid-promoted allylation of azetidin-2-ones
作者:S.S. Bari、P. Venugopalan、Renu Arora
DOI:10.1016/s0040-4039(02)02775-2
日期:2003.1
Exposure of 3alpha-chloro-3-phenylthioazetidin-2-ones and allyl trimethyl si lane to a Lewis acid promotes a remarkably facile and stereoselective C-3 allylation to give 3alpha-allyl-3-phenylthioazetidin-2-ones 4 in excellent yield. These allylated azetidin-2-ones undergo smooth desulphurization with tri-n-butyltin hydride or Raney-nickel producing cis-3-allyl- and cis-3-propylazetidin-2-ones. (C) 2003 Elsevier Science Ltd. All rights reserved.