Stereocontrolled synthesis of N-vinyl-, N-(1'-propenyl)-, and N-unsubstituted-.beta.-lactams from 2-aza-1,3-butadienes via the Staudinger reaction
摘要:
2-Aza-1,3-butadienes 2 and 5 were synthesized in good yields and on a large scale. Reaction of 2 and 5 with acid chlorides in the presence of triethylamine (Staudinger reaction) resulted in the high-yielding formation of N-vinyl- and N-(1'-propenyl)-beta-lactams. Excellent cis-stereoselectivity was observed in the reaction of 2-aza-1,3-butadienes 2 and 5 with Bose-Evans ketenes and Sheehan ketenes, whereas reaction with a Moore ketene gave, as expected, a trans beta-lactam. N-Formyl, N-vinyl, and N-(1'-propenyl) groups at the beta-lactam nitrogen could be cleaved oxidatively in one step and in good yields by treatment with potassium permanganate. It was also found that the N-vinyl group can be removed successfully under hydrolytic, conditions to yield N-unsubstituted-beta-lactams.
A diastereoselective synthesis of (±) cis-β-lactams (5 & 6) via cycloaddition reactions of N1-(α-thiophenyl)benzyl imines (3) with acid chlorides (4) in the presence of triethylamine is described. The deprotection of N1-(α-thiophenyl)benzyl group has been achieved by oxidation using potassium persulfate to give N-unsubstituted β-lactams (7) in good yields.
A diastereoselective synthesis of (+/-) cis-beta-lactams (5 & 6) via cycloaddition reaction of N-1-(alpha-thiophenyl)benzyl imines (3) with acid chlorides (4) in the presence of triethyl amine is described. Deprotection of N-1-(alpha-thiophenyl)benzyl group was achieved in good yields by oxidation using potassium persulfate. (C) 1997 Elsevier Science Ltd.