D A. Evans [2,31-Sigmatropic Rearrangements: Introduction-2 Chem 206 IX-O, Y=C; Wittig-like Rearrangements IX-S,Y=O; Sulfoxide Rearrangement R R OMe Buchi JAcs 1974. 96. 5563 Accts. Chem. Res. 1974. 7. 147 IX-Se, Y= N; Related Rearrangement n thinking about this rearrangement, also consider the carbenoid res R2 IX-O,Y= C; An all-carbon Rearrangement NH-Ts Se Ts R2 ns. Tet Let. 198 R okins JOC 1984 Hopkins, JOC 1985, IX-S,Y=N; Related Rearrangement note that the product contains the retrons TS-N-Cl Smith, Chem. Commun. 1974, 695: Smith, JOC 1977, 42, 3165 ■X·N,Y=o; Meisenheimer Rearrangement R2 LR3Zn/HOAc R2 85% yield overall Dolle. Tet let 1989. 30. 4723 Tanabe. Tet Let. 1975. 3005N Me Me O R2 R1 R3 + – R2 R1 R3 OH R1 R3 R2 N N O H OMe OMe NMe2 –N2 Cu(I) C NMe2 O R2 R1 R3 O R1 R3 R2 C NMe2 O H R2 R1 R3 C O R1 R3 R2 O R2 R1 R3 NMe2 R2 R1 R3 OR O ROH R2 R1 R3 Se Ar N Ts S Ar O R1 R3 R2 S TsO Ph Ts–N–Cl Na+ Se Ar N R2 R1 R3 Ts R1 R3 R2 O S Ar S Ph TsO N Ts BuLi PhSCl R1 R3 R2 O N Me Me N Ts R1 R3 R2 OH N TsO Ts SPh N Ts TsO R2 R1 R3 OH NH–Ts R1 R3 R2 (MeO)3P NaOH keq < 1 note that the product contains the retrons for the enolate Claisen rearrangement Smith, Chem. Commun. 1974, 695; Smith, JOC 1977, 42, 3165 ■ X - O, Y = C; An all-carbon Rearrangement : D. A. Evans [2,3]-Sigmatropic Rearrangements: Introduction-2 Chem 206 In thinking about this rearrangement, also consider the carbenoid resonance form as well : – + 140 °C ■ X - O, Y = C; Wittig-like Rearrangements Buchi, JACS 1974, 96, 5563 – Hopkins, Tet Let. 1984, 25, 15 Hopkins, JOC 1984, 49, 3647 ✻ ✻ ■ X - S, Y = N; Related Rearrangement + ✻ selenophile Evans, Accts. Chem. Res. 1974, 7, 147 ✻ thiophile – + ■ X - S, Y = O; Sulfoxide Rearrangement ✻ ✻ Hopkins, JOC 1985, 50, 417 ■ X - N, Y = O; Meisenheimer Rearrangement Zn/HOAc Tanabe, Tet Let. 1975, 3005 ■ X - Se, Y = N; Related Rearrangement – [2,3] 85% yield overall – Dolle, Tet Let. 1989, 30, 4723