The synthesis of β-lactams via a one-pot Reformatsky reaction of imines promoted by Zn/Cp2TiCl2 (cat.)
In the presence of Zn/Cp2TiCl2 (cat.) α-bromoacetates, γ-bromocrotonates or α-bromomethylacrylates react with imines in one-pot to form β-lactams, 3-vinyl-β-lactams or α-methylene-γ-lactams, respectively, at room temperature without
Diastereoselective Synthesis of syn-β-Lactams Using Rh-Catalyzed Reductive Mannich-Type Reaction of α,β-Unsaturated Esters
The combination of Et2Zn and RhCl(PPh3)3 led to the facile generation of a rhodium-hydride complex (Rh-H) that catalyzed the 1,4-reduction of α,β-unsaturated esters. The resulting rhodium enolate performed as a Reformatsky-type reagent and reacted with various imines to give syn-β-lactams in good to excellent yields with high diastereoselectivity.
Synthesis of β-lactams by condensation of the tin enolates of 2-pyridylthioesters with imines. A comparison between titanium and tin enolates
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.
Annunziata, Rita,Benaglia, Maurizio,Cinquini, Mauro,Cozzi, Franco,Raimondi, Laura
p. 5821 - 5828
(2007/10/02)
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