The condensation of the titanium enolates of C-2 alkyl substituted 2-pyridylthioesters with imines affords beta-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 p-lactams, while sterically non-requiring or chelating groups favour the formation of the cia-products. On the basis of NMR evidences a rationale is proposed to account for the observed stereoselectivity.
SYNTHESIS OF BETA-LACTAMS BY CONDENSATION OF TITANIUM ENOLATES OF 2-PYRIDYLTHIOESTERS WITH IMINES - INFLUENCE OF THE IMINE STRUCTURE ON THE TRANS/CIS STEREOSELECTIVITY / R. ANNUNZIATA, M. BENAGLIA, M. CINQUINI, F. COZZI, F. PONZINI, L. RAIMONDI. - In: TETRAHEDRON. - ISSN 0040-4020. - 50:9(1994), pp. 2939-2948.
SYNTHESIS OF BETA-LACTAMS BY CONDENSATION OF TITANIUM ENOLATES OF 2-PYRIDYLTHIOESTERS WITH IMINES - INFLUENCE OF THE IMINE STRUCTURE ON THE TRANS/CIS STEREOSELECTIVITY
R. ANNUNZIATAPrimo
;M. BENAGLIASecondo
;M. CINQUINI;F. COZZI;L. RAIMONDIUltimo
1994
Abstract
The condensation of the titanium enolates of C-2 alkyl substituted 2-pyridylthioesters with imines affords beta-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 p-lactams, while sterically non-requiring or chelating groups favour the formation of the cia-products. On the basis of NMR evidences a rationale is proposed to account for the observed stereoselectivity.
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