Diastereoselective One-Pot Synthesis of Oxazolines Using Sulfur Ylides and Acyl Imines
作者:Md Shafaat Al Mehedi、Jetze J. Tepe
DOI:10.1021/acs.joc.9b00883
日期:2019.6.7
This work describes an extended version of the Corey–Chaykovsky reaction to access oxazolines using sulfur ylides and stable precursors of acyl imines. The reaction proceeds through a mixture of aziridines and oxazolines, which provides the trans-oxazolines following in situ Heine-type aziridine ring expansion upon treatment with BF3·OEt2. Following the same one-pot procedure, amidine imides react
Bifunctional Asymmetric Catalysis
with Hydrogen Chloride: Enantioselective Ring Opening of Aziridines
Catalyzed by a Phosphinothiourea
作者:Eric Jacobsen、Tsuyoshi Mita
DOI:10.1055/s-0029-1217344
日期:——
Ring-opening of aziridines with hydrogenchloride to form β-chloroamine derivatives is catalyzed by a chiral phosphinothiourea derivative in high yields and with high enantioselectivities. On the basis of (31)P NMR studies, activation of HCl appears to proceed via quantitative protonation of the catalyst to afford a phosphonium chloride complex.
Ring opening of aziridines by different fluorinating reagents: three synthetic routes to .alpha.,.beta.-fluoro amines with different stereochemical pathways
作者:Gerard M. Alvernhe、Christine M. Ennakoua、Sylvie M. Lacombe、Andre J. Laurent
DOI:10.1021/jo00337a024
日期:1981.11
Archier-Jay, Danielle; Besbes, Neji; Laurent, Andre, Bulletin de la Societe Chimique de France, 1989, # 44, p. 537 - 543
作者:Archier-Jay, Danielle、Besbes, Neji、Laurent, Andre、Laurent, Eliane、Lesniak, Stanislaw、Tardivel, Robert
DOI:——
日期:——
Single electron transfer versus nucleophilic ring opening in reactions of cis-trans pairs of activated 2-phenylaziridines. Strong influence of nitrogen pyramid for N-benzoylaziridines
Activated 2-phenylaziridines with a second substituent R in position 3 were made to react with xanthyl anion X-. Nucleophilic ring opening ia the only reaction that occurs with sulfonyl activation. The analogous N-benzoylaziridines 1 undergo this type of ring opening when the two substituents Ph and R are trans. The cis isomers (cis-1, Ph and R cis) react in this manner to a negligible extent if any. The (nearly) exclusive ring cleavage reaction of cis-1 is C-N homolysis of an intermediate ketyl formed by single electron transfer (SET) from X-. This cis-trans phenomenon is in accordance with the hypothesis that the two competing reactions depend in an opposite manner on the steepness of the nitrogen pyramid. A predominant or exclusive final result of SET is reductive aziridine opening and dimerization of the xanthyl radical X.. Formation of both diastereomers of the[GRAPHICS]amidoethylated xanthene in one case (R = Me) is evidence for a cross combination of X. with the radical formed by homolytic ring opening. Cross combination is also a likely path for R = H (no cis-trans isomerism), in addition to reductive ring opening. cis-Aziridines with dimethylcarbamoyl on nitrogen do not react via SET since the ketyl is not stabilized and therefore difficult to generate. Carbonyl attack on both types of acylaziridines competes more or less successfully with the two ring cleavage reactions.