M. Shair, K Beaver Carbene heteroatom Transformations: Sulfonium Oxonium Ylids Chem 206 Ring expansion reactions have been investigated Yide formation I Methods based on sulfur ylides: (review) Vedejs, Accts. Chem. Res. 1984, 17, 358 catalyst Cu(O) COEt Reviews: Padwa. Chem. Rev. 1991 263 Padwa. Chem. Rev. 1996 223 Bames, Evening Seminar, March 16, 1993 is generally S, O or N and can be sp? or sp hybridized Ylides often undergo sigmatropic rearrangements or cycloadditions EtO2C [2, 3]-sigmatropic rearrangement Vedejs, JACS 1989, 111, 8430 00 OMe Rh2(oAc)4 Kido and Kato, Jcs Perkins 1 1992 229 Pirrung et al JACS, 1991, 113, 8561. OMe Stevens Rearrangement ([1, 2] alkyl shift) h2(oAc) Cua) ⑥R2 West, JACS 19931177 1M. Shair, K. Beaver Chem 206 Ylide Formation R N2 OEt O catalyst R X OEt O R R X is generally S, O or N and can be sp2 or sp3 hybridized Ylides often undergo sigmatropic rearrangements or cycloadditions Reviews: Barnes, Evening Seminar, March 16, 1993 Padwa, Chem. Rev. 1991 263 Padwa, Chem. Rev. 1996 223 [2,3]-Sigmatropic rearrangement: Stevens Rearrangement ([1,2] alkyl shift): R2 N N2 R1 O Rh2 (OAc)4 N O R1 R2 N O R2 R1 West, JACS 1993 1177 OMe SPh O N2 O S Ph O E SPh E Acorenone B O Kido and Kato, JCS Perkins 1 1992 229 Vedejs, JACS 1989, 111, 8430 Methynolide has been synthesized by Vedejs using this ring-expansion methodology 72% 72% 50% Methods based on sulfur ylides: (review) Vedejs, Accts. Chem. Res. 1984, 17, 358 Ring expansion reactions have been investigated S N2 CO2Et S CO2Et S CO2Et S S Et O Me O TfO CO2Et S EtO2C Me Me OH HO Me O Carbene Heteroatom Transformations: Sulfonium & Oxonium Ylids OMe Cl MeO CO2Me O N2 O Me Me OMe Cl MeO O Me CO2Me O OMe Cl MeO O O O OH Me griseofulvin Pirrung et al JACS, 1991, 113, 8561. Me Cu(I) O H AcO H Me O N2 AcO O Me O AcO O Me O Cu(I) or Rh(II) Clark et al. Tetrahedron Lett. 1996, 37, 5605. R2X Rh2 (OAc)4 DBU KOt-Bu Rh2 (OAc)4