Synthesis of β-lactams by condensation of titanium enolates of 2-pyridylthioesters with imines. Influence of the imine structure on the trans/cis stereoselectivity
The condensation of the titanium enolates of C-2 alkyl substituted 2-pyridylthioesters with imines affords β-lactams in trans/cis ratios that largely depend on the structure of the C-imine residue. Bulky and non-chelating heteroatom-containing groups lead to the formation of trans β-lactams, while sterically non-requiring or chelating groups favour the formation of the cis-products. On the basis of NMR evidences a rationale is proposed to account for the observed stereoselectivity.
Annunziata, Rita,Benaglia, Maurizio,Cinquini, Mauro,Cozzi, Franco,Ponzini, Francesco,Raimondi, Laura
p. 2939 - 2948
(2007/10/02)
MILD AND CONVENIENT ONE-POT SYNTHESIS OF β-LACTAMS BY CONDENSATION OF TITANIUM ENOLATES OF 2-PYRIDYLTHIOESTERS WITH IMINES
Treatment of 2-pyridylthioesters with triethylamine in the presence of titanium tetrachloride affords titanium enolates that add to imines to give β-lactams in fair to excellent yields with moderate to good stereoselectivity.
Preparation of 3-Alkyl β-Lactams via the Ketene-Imine Cycloaddition Reaction Using α-(Phenylthio)alkanoyl Halides as Starting Materials:Application to the Synthesis of (+/-)-Carbapenem Building Blocks and Related Compounds
Preparation of appropriately substituted 3-alkyl β-lactams via the ketene (or equivalent)-imine cycloaddition reaction is described.The dehydrochlorination reaction of α-(phenylthio)alkanoyl chlorides with triethylamine in the presence of imines derived f
Palomo, Claudio,Cossio, Fernando P.,Odiozola, Jose M.,Oiarbide, Mikel,Ontoria, Jesus M.
p. 4418 - 4428
(2007/10/02)
A Convenient Method for β-Lactam Formation from β-Amino Acids Using Phenyl Phosphorodichloridate Reagent
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Palomo, Claudio,Aizpurua, Jesus M.,Urchegui, Raquel,Iturburu, Miren,Retana, Ana Ochoa de,Cuevas, Carmen
p. 2244 - 2247
(2007/10/02)
Asymmetric synthesis of β-lactams and the carbapenem antibiotic (+)-PS-5
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Hart,Chih-Shone Lee,Pirkle,et al.
p. 6054 - 6056
(2007/10/02)
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