D. A. Evans. D. Barnes Carbonyl Ylids: Dipolar Cycloaddition (and More! ) -3 Chem 206 The Carbonyl Ylide- Azomethine"Dipole Cascade The Synthesis of Furan CHOCH °C HC三c-Co2CH o not observed rearrange I HCEC-CO2CH3 eOc Methyl vinhaticoate CO, CH3 Spencer, T.A, et al. JACS 1967, 89, 5497. Can you propose a rational mechanism for this transformation? CO Me Me Co/Me The 1, 3-proton shift is catalyzed by trace amounts of water. Azomethine ylide formation requires a proton at the tertiary center Padwa.A: Dean. D. C. Zhi L. J. Am. Chem. Soc. 1989. 111 6451 Cu(acac) cc.1992,114,59360 The Synthesis of Furans HO CO2 CH3 160° 2-methoxymethylenecholestanone-3 CHO CO2CH3 pencer Tetrahedron Let. 1967, 1865-1867. Hildebrandt, Tetrahedron Let. 1988. 29, 2045-2046D. A. Evans, D. Barnes Chem 206 N CHN2 Me O O N O O H Me CO2Me HC C CO2CH3 The Carbonyl Ylide - Azomethine "Dipole Cascade" Padwa, A.; Dean, D. C.; Zhi, L. J. Am. Chem. Soc. 1989, 111, 6451-6452. Padwa, A.; Dean, D. C.; Zhi, L. J. Am. Chem. Soc. 1992, 114, 593-601. The 1,3-proton shift is catalyzed by trace amounts of water. Azomethine ylide formation requires a proton at the tertiary center. N O O Me N O O Me MeO2C N O O Me N Me CO2Me O O H H N Me CO2Me OH O not observed HC C CO2CH3 Intermolecular addition to a,b-unsaturated carbonyls Spencer Tetrahedron Lett. 1967, 1865-1867. 2-methoxymethylenecholestanone-3 29% CuSO4 160 °C The Synthesis of Furans OMe O OMe O O EtO2C EtO2C Et O CHN2 O Cu(acac)2 Hildebrandt, Tetrahedron Lett. 1988, 29, 2045-2046. 89% CO2CH3 O O O O N2 CH3O CO2CH3 O O O CH3O HO Can you propose a rational mechanism for this transformation? O O O O CO2CH3 CH3O CO2CH3 O O O CH3O O Methyl vinhaticoate hydrolysis decarboxylation ~30% CuSO4 160 °C Spencer, T. A., et. al. JACS 1967, 89, 5497. O CHOCH3 Me CO2CH3 Me Me Me CO2CH3 Me Me EtO CHN2 O O CO2Et Me CO2CH3 Me Me O The Synthesis of Furans rearrange Carbonyl Ylids: Dipolar Cycloaddition (and More!)–3 Rh2 (OAc)4