Reaction of -silyl imines with silyi keteneacetals in the presence of ZnI2 and t-butyl alcohol, followed by treatment of the intermediate -silyl β-aminoesters with MeMgBr, produces -silyl-azetidin-2-ones in good yield; use of trimethylsilyl triflate as Lewis acid catalyst can be advantageous in some cases. The preparation of the -t-butyldimethylsilyl imine of ethyl glyoxylate in this context is detailed
Preparation of aminosaccharides using ester-imine condensations: syntheses of methyl -benzoylacosaminide and methyl -[oxo(phenylmethoxy) acetyl)daunosaminide from (S)-ethyl 3-hydroxybutyrate
作者:Judith C. Gallucci、Deok-Chan Ha、David J. Hart
DOI:10.1016/0040-4020(89)80126-7
日期:1989.1
The dianion of (S)-ethyl β-hydroxybutyrate (1) was treated with -trimethylsilyl Imine 2 to afford β-lactam 4. The same dianion reacted with -ary1 imine 10 to give β-lactams 11, 12, and 13. A three-step sequence was used to convert 4 into the β-lactam-pyran hybrid 9 while a five-step sequence was developed to transform 11 and 12 into 9. Application of the carboxyinversion reaction to derivatives of
.beta.-Lactams from esters and sulfenimines: a new route to monobactams
作者:Duane A. Burnett、David J. Hart、Jun Liu
DOI:10.1021/jo00360a061
日期:1986.5
Synthesis of Medium Ring Nitrogen Heterocycles via a Tandem Copper-Catalyzed C−N Bond Formation−Ring-Expansion Process
作者:Artis Klapars、Sean Parris、Kevin W. Anderson、Stephen L. Buchwald
DOI:10.1021/ja038565t
日期:2004.3.1
A simple method for the preparation of medium ring heterocycles (7-, 8-, 9-, and 10-membered) has been developed. The process employs a Cu-catalyzed coupling of beta-Iactam with an aryl bromide or iodide followed by intramolecular attack of a pendant amino group. In some instances, the intermediate beta-lactam is observable but can be converted to the aza-heterocycle by catalysis. Acetic acid was found to be superior to transition metal complexes as a catalyst for this ring-expansion process.