D A. Evans Johnson Eschenmoser Claisen Rearrangements Chem 206 Johnson Orthoester Claisen Eschenmoser- Claisen Lead paper. Johnson, Faulkner, Peterson, JACS 1970, 92, 741 Eschenmoser. A. Helv. Chem. Acta 1964. 47 2425: He/v. Chim Acta 1969. 52. 1030 EtCo2H(cat) Me-C-oEt Eto oEt Et2N OMe I Compare the two variants CH3CH2 H(cat) Eto2C CH3C(NMe2)(OMe)2 38°c M 60% Hg(OAc)2.EVE High yield, E:Z= 99:1 98°c CH2=C(OMe)NEI2) Me2N OHC 98%(EZ=86:14) Xylene,140°C,14h The Saucy Marbet Alternative a Synthesis of Amide Acetals NMe, EtOH Me NMe2 94% 125°C C3H5 diastereoselection 6. 1 oEt Me evenson Tet Let. 1991. 32 4199 OL Saucy, Marbet, He/v. Chim. Acta 1967, 50, 2091, 2095 Me2(oBn) CMez(oBn Welch, JACS 1987Et O Et Et OEt Me NMe2 N Me OMe C3H5 R N O Me Me BF4 - + + + OH Me C OEt OEt OEt EtO OEt Me O OH OEt O O OEt Me S Me OH Me EtO2C Me O Me Me Me OHC Me Et2N OMe O O Me H NMe2 Et OH Et Me CO2Me OH Me Me OH Me Me Me NMe2 O Me Me O Me OH Me Me Me Me OMe Et2N OMe Me OLi CMe2(OBn) O N Me Me Me OLi N Et OMe CMe2 (OBn) O Me Me Me Me Me O Me Me Me CHO Me Me Me Me OMe Me OEt H3PO4 D CH3C(OEt)3 CH3C(NMe2)(OMe)2 CH2=C(OMe)(NEt2) Et2O EtOH NaOEt CO2Me Me O Me2N Me O NEt2 NEt2 O Me NMe2 EtO OEt Et Me NMe2 O H ■ Reactions to ponder: 60% 94% 125oC 125oC H3PO4 or TsOH The Saucy Marbet Alternative Saucy, Marbet, Helv. Chim. Acta 1967, 50, 2091,2095 EtCO2H (cat) + Predict the major diastereomer Welch, JACS 1987, 109, 6716 Stevenson, Tet. Let. 1991, 32, 4199 diastereoselection 6:1 Predict the major diastereomer ■ Compare the two variants: 92% (E:Z = 98:2) 98% (E:Z = 86:14) 60% 138oC 98oC Hg(OAc)2 , EVE CH3CH2CO2H (cat) ■ Lead paper: Johnson, Faulkner, Peterson, JACS 1970, 92, 741 Johnson Orthoester Claisen D. A. Evans Johnson & Eschenmoser Claisen Rearrangements Chem 206 ■ Synthesis of Amide Acetals Eschenmoser-Claisen Eschenmoser, A. Helv. Chem. Acta 1964, 47, 2425; Helv. Chim.Acta 1969, 52, 1030. Xylene, 150oC Xylene, 110oC High yield, E:Z = 99:1 Faulkner and Peterson Xylene, 140oC, 14h 70%