LIGAND-CONTROLLED ALPHA-REGIOSELECTIVITY IN PALLADIUM-CATALYZED ARYLATION OF BUTYL VINYL ETHER

The palladium-catalyzed arylation of olefins (Heck reaction) is an extremely useful process for carbon-carbon bond formation;1,2 unfortunately the use of acyclic enol ethers in this reaction is limited by poor α/β-regioselec-tivity (Figure 1). Preferential β-attack was observed with aromatic substrates bearing electron-withdrawing groups and when chloride or bromide anions are present in the oxidative addition intermediate. 3 On the other hand, high selectivity for the a position in acyclic systems has so far been observed only in a few cases4a,b and in reaction between vinyl triflates and enol ethers4C. © 1990, American Chemical Society. All rights reserved.