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1、Unimolecular Sigmatropic RearrangementNo cyclic intermediatesCyclic transition statesThe reaction converted process:1,3- Rearrangement2,3- Rearrangement3,3- RearrangementX=C: Cope RearrangementX=O: Claisen RearrangementLewis Acid Mediated Asymmetric 2,3-Sigmatropic Rearrangement of Allylic Amines. S
2、cope and Mechanistic InvestigationJan Blid, Olaf Panknin, Pavel Tuzina, and Peter Somfai 1. Cope Rearrangement(1). The reaction is both stereospecific and stereoselective.a. It is stereo-specific in that a Z or E configurational relationship at either double bond is maintained in the transition stat
3、e and governs the stereo-chemical relationship at the nearly formed single bond in the product.b. The stereo-selectivity: a chair-like transition state in which the larger substituent (at C-3 or C-4) adopts an equatorial-like conformation. HCH3H3CPhERPhCH3HCH3PhH3CCH3HPhH3CCH3HZRPhCH3HCH3ES(3R, 5Z)
4、13%(3S, 5E) 87%The products corresponding to boat-like transition states are usually not observed for acyclic dienes H3CPhCH3ERH3CPhCH3ERH3CPhCH3HERCH3PhCH3CH3PhCH3CH3PhCH3HSZ(3R, 5E)(3S, 5Z)350oC1h100%-40oC100%(2). Cope Rearrangement-reversible processes: No changes: The number or type of bonds, th
5、e total bond energy, So the equilibrium is governed by the relative stability of the starting material and product OHO320oC90%Base-catalyst (hydroxyl group: its alkoxide) the reaction is accelerated by factors of 1010-1017!K+Na+Li+ OHOOHHHOKHKH / THFreflux 18h98%18-Crown-625oC, 18h75%(3). Several tr
6、ansition metal species (such as Pd(II) salts) have been found to catalyze Cope rearrangements and / or have stereoselectivity.MePhMeMePhMeMeHMeSPhMeMeMeHR+Thermal 240oC1:1PdCl2(CH3CN)2, 25oC7:3Chem. Rev. 1984, 84, 205OOallylic alcohols ,-unsaturated carbonyl compounds2. Claisen Rearrangement The typ
7、e of reactiona. Vinyl ether:CCHORH2CCHCH2OHH2CCHOEt+Hg(OAc)2H2CCHCH2OCHCH2CHO96%OCHCH2105oCCH2CHO87%CHCH2CH3CH3COHCH2COCH3CH3+125oCH+OOOHOCH3+OOOHRCOOH110oCOHnNaBH4OHRH3CCOCH3OCH3OCH3+ORCH3COCH3OCH3ORCOCH3CO2CH3Rb. The orthoester modificatiuon140oCNCH2PhHOCH2CH3NCH2PhCH2CH3CH2CO2CH3CH3C(OCH3)374%145
8、oCNCH3CH2OHCH3CH2CH2C(OCH3)3ONCH3OCHCO2CH3CH2CH396%c. Amide acetal:RCHCHCH2OHH3CCOCH3NMe2OCH3ORCH3COCH3NMe2ORCNMe2CONMe2R+CHRCHR2OHOCH2OCCH2OSiMe3CHRCR2OHOSiMe3CH2CHCH2CH2CO2HCH3OOSiMe3RRROOHRRRH2Od. Ester of allylic alcohols via trimethylsilyl ether of the esterenolate to unsaturated carboxylic aci
9、ds1. LiNR22. Me3SiCl1. 67oC2. CH3OH3. H2O70%PhOCHOCH2CHCH3CH2Ph CO-COCH2CHCH3CH2PhCOHCOCH3CH2CHCH2e. Enolates of a-allyloxy ketonesThe reaction shows a high sensitivity to the metal cation and the solvent: K+Na+Li+, and THFtoluenea-hydroxy-a-allyl ketonesOOH3COOCH3OHOHH3COOCH3OH3COOCH3OH3COOCH3HOHf.
10、 Allyl phenyl ethersortho, or para- allyl phenols180oCClaisenCope88%MeMeHCHOOHMeMeOHMeOMeiso-PrenolPrenol+OxidationIsomerisationOMeMeMeH2OMeMeMeOMeMeMeCHO柠柠檬檬醛醛ClaisenCope单元操作1单元操作2单元操作3Facile 1,3-diaza-Claisen Rearrangements of TertiaryAllylic Amines Bearing an Electron-Deficient AlkeneRachel M. Aranha, Amy M. Bowser
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