M.C. White, Chem 153 JE-Allyl chemistry -347- Week of December 2. 2002 Olefin geometry clature of o the internal PdLn anti disfavored swnT: favored For sterically hindered olefins, the rate anti/syn isomerization is often slow relative to Nu attack, thus the initial lefin geometry is preserved in the product Trost JACS 1980(102)4730 CO,Me geranyl acetate(E 92%, only E somer observed So Ph by NMr neryl acetate( 2)OAc 78%, only the ZCO2Me observed by Nmr SOPh terically unhindered olefins, the rate of isomerization may be rapid and favors the syn T-allyl intermediate. This feature can used to synthesize stereodefined ionalized e olefins from terminal olefins Pd(Ppha) cat 个幽R八N OAc *Na 77%. the e (cis trans, 9: 1) exclusivelyM.C. White, Chem 153 π-Allyl chemistry -347- Week of December 2, 2002 Olefin geometry OAc CO2Me SO2Ph CO2Me SO2Ph Na OAc CO2Me SO2Ph geranyl acetate (E) 92%, only E isomer observed by NMR Pd(PPh3)4 cat. 78%, only the Z isomer was observed by NMR neryl acetate (Z) THF For sterically unhindered olefins, the rate of isomerization may be rapid and favors the syn π-allyl intermediate. This feature can used to synthesize stereodefined, functionalized E olefins from terminal olefins. OAc CO2Me Na SO2Ph Pd(PPh3)4 cat. Nu 32% Nu 30% + + regioisomer (38%) (cis:trans, 9:1) THF R OAc CO2Me Na SO2Ph Pd(PPh3)4 cat. THF R Nu 77%, the E isomer was formed exclusively Trost JACS 1980 (102) 4730. For sterically hindered olefins, the rate anti/syn isomerization is often slow relative to Nu attack, thus the initial olefin geometry is preserved in the product: R R R H OAc OAc PdLn H R H H PdLn H R PdLn H R R Nu R Nu Z E anti: disfavored syn: favored η3/η1 η1/η3 Nu Nu anti/syn nomenclature of η3 π-allyl is relative to the internal H of the allyl group Z E PdLn anti/syn isomerization