M.C. White, M.s. Taylor Chem 153 Olefin Nu attack -330 Week of November 25, 2002 Palladium(1-mediated 3, 3/-sigmatropic rearrangements OAc PdCl(MeCN) (10mo%) Bno BnO OB THF.23° OAc 82% BnOH2( BnOc (10mol%) Clpd ChPd THF.23°C Chpd- CH3 Saito tl1988(29)1157 The vinyl ether I is unreactive to Pd(ii) catalysis. However, the similar substrate 2 shows good reactivity PdCl(Mech PdCl(MeCN)h (10mol%) Recovered starting THF23°C kelhaupt1986(27)6267 The authors speculate that when reacting with 1, Pd(n) binds preferentially to the electron-rich vinyl ether olefin over the terminal olefin. Such binding does not lead to a productive reaction. When the steric bulk of the vinyl ether is increased, as in 2, binding to the vinyl ether is less favourable Pd(in)coordination to the terminal allylic olefin occurs resulting in catalysis of the Claisen rearrrangement. Note that these structural requirements limit the scope of this reaction.M.C. White,M.S. Taylor Chem 153 Olefin Nu attack -330- Week of November 25, 2002 Cl2Pd O O CH3 R BnOH2C BnO OBn OAc OAc Cl2Pd O O R BnOH2C CH3 BnO OBn OAc OAc Cl2Pd O O CH3 R BnOH2C PdCl2(MeCN)2 (10 mol%) THF, 23°C 82% BnO OBn OAc OAc PdCl2(MeCN)2 (10 mol%) THF, 23°C Palladium (II)-mediated [3,3]-sigmatropic rearrangements Saito TL 1988 (29) 1157. Et O Et O Me Et O Me The vinyl ether 1 is unreactive to Pd(II) catalysis. However, the similar substrate 2 shows good reactivity: PdCl2(MeCN)2 (10 mol%) THF, 23°C Recovered starting material 1 PdCl2(MeCN)2 (10 mol%) THF, 23°C 71% The authors speculate that when reacting with 1, Pd(II) binds preferentially to the electron-rich vinyl ether olefin over the terminal olefin. Such binding does not lead to a productive reaction. When the steric bulk of the vinyl ether is increased, as in 2, binding to the vinyl ether is less favourable. Pd(II) coordination to the terminal allylic olefin occurs resulting in catalysis of the Claisen rearrrangement. Note that these structural requirements limit the scope of this reaction. 2 Bickelhaupt TL 1986 (27) 6267