A solvent-free, catalytic, one-potsynthesis of β-lactams is described. The reaction involves the reaction between silyl ketene thioacetals derived from 2-pyridyl thioesters and imines at room temperature in the presence of catalytic amounts of Sc(OTf)3 and in the absence of solvent. Extension of this procedure to the synthesis of an enantiomerically pure azetidinone, a precursor of industrially relevant
Mechanistic Investigations of the ZnCl<sub>2</sub>-Mediated Tandem Mukaiyama Aldol Lactonization: Evidence for Asynchronous, Concerted Transition States and Discovery of 2-Oxopyridyl Ketene Acetal Variants
作者:Cunxiang Zhao、T. Andrew Mitchell、Ravikrishna Vallakati、Lisa M. Pérez、Daniel Romo
DOI:10.1021/ja209163w
日期:2012.2.15
The ZnCl(2)-mediated tandem Mukaiyama aldol lactonization (TMAL) reaction of aldehydes and thiopyridyl ketene acetals provides a versatile, highlydiastereoselective approach to trans-1,2-disubstituted β-lactones. Mechanistic and theoretical studies described herein demonstrate that both the efficiency of this process and the high diastereoselectivity are highly dependent upon the type of ketene acetal
A series of silylketene thioacetals derived from 2-pyridylthioesters have been prepared and the configuration of some of them has been determined by NMR spectroscopy. In the presence of Lewis acids these compounds stereoselectively react with imines to afford β-lactams in a convenient one-pot procedure. An enantioselective β-lactam synthesis promoted by a chiral Lewis acid is also described.
pyridylthioacetals with imines in pure water was studied. The reaction of the phenylthioacetal derivatives brings always to β-aminoesters; the reaction of pyridylthioacetals leads to the stereoselective formation of β-lactams in organic solvents, while in the presence of a large amount of water affords β-amino amides in good yields. That represents a new, easy, one-pot catalytic synthesis in water of an interesting
Reactivity of the Pyridylthiosilyl Enol Ether — Route to b-Lactone and b-Lactam —
作者:Koichi Hirai、Hiroshi Homma、Isamu Mikoshiba
DOI:10.3987/com-93-6604
日期:——
A simple and facile method for beta-ractone and beta-lactam syntheses based on a Lewis acid promoted pyridylthiosilyl enol ether (1) addition to an aldehyde or Schiff base is described.