Synthesis of β-lactams by condensation of the tin enolates of 2-pyridylthioesters with imines. A comparison between titanium and tin enolates

Article abstract of DOI:10.1016/S0040-4020(01)85649-0

Addition of triethylamine to a mixture of 2-pyridylthioesters and SnCl₄ or SnBr₄ affords the corresponding tin(IV) enolates that add to imines to give β-lactams in fair to good yields and with various degree of trans/cis stereoselectivity. Examples of highly diastereofacially selective reactions carried out on a chiral thioester and on a chiral imine are also reported. The results are compared with those obtained in the condensations promoted by TiCl₄ and TiBr₄.