The Synthesis of Enol Ethers Ylide formation by the Interaction of Carbenoids with Carbonyl Lone Pairs 人 33584 Bien, S: Gillon, A; Kohen, S. J. Chem. Soc. Perkin Trans. 1. 1976. 489-492 he carbene precursor of choice is a Rh2(pfb)4 CHat-Bu insertion Nt-BU PhH, reflux most common method involves catalytic amounts of etals, such as copper or rhodium. CH2-Bu 16-H transfer Doyle, M. P. Taunton, J ; Pho. H. Q. Tetrahedron Lett. 1989. 30, 5397 35B-08 Ylides3/179311:17AM- Generally, the carbene precursor of choice is a diazoalkane or, more frequently, an α-diazocarbonyl. These can be decomposed via thermolysis or photolysis. However, the most common method involves catalytic amounts of transition metals, such as copper or rhodium. + Ylide Formation by the Interaction of Carbeneoids with Carbonyl Lone Pairs pfb = perfluorobutyrate Doyle, M. P., et al. J. Org. Chem. 1991, 56, 820-829. Doyle, M. P.; Taunton, J.; Pho, H. Q. Tetrahedron Lett. 1989, 30, 5397. 1,6-H transfer + insertion products - + Rh2(pfb)4 PhH, reflux The Synthesis of Enol Ethers + - Bien, S.; Gillon, A.; Kohen, S. J. Chem. Soc. Perkin Trans. I. 1976, 489-492 catalyst 1 2 catalyst Temp (°C) %1 %2 Pd2Cl2(C3H5)2 Cu(PhCOCHCOMe)2 (MeO)3PCuI Rh2(OAc)4 None RT 80 RT RT 80 53 50 3 1 15 3 13 35 58 54 H+ R1 R2 O R1 O R2 M EtO CHN2 O O EtO O O MLn O EtO2C O O EtO O O EtO O OEt O H3C N t-Bu O O N2 CO2Et O N O O EtO O N O O EtO CH2t-Bu CH2t-Bu L4Rh2 O N OH O EtO CH2t-Bu 35B-08 Ylides 3/17/93 11:17 AM