Palladium catalysed cyclisations creating products possessing spiro-, fused- and bridged-rings, and tetrasubstituted carbon centres as mixtures of double bond isomers are modified to give single products in the presence of Tl(1) salts.
Enamides derived from o-iodobenzoic acid and Z-3-bromoacrylic acid undergo regiospecific palladiumcatalysed exo-trig cyclisation onto a proximate alkene to give spirocyclic products in good to excellent yield. Double bond isomerisation in the product is not usually observed and is retarded by the addition of tetraethylammonium chloride which also allows the reaction to be carried out under milder
Various N-vinyl- and N-allyl-amides of 2-iodobenzoic acid undergo catalytic cyclisation in the presence of tetraethylammonium chloride and a palladium acetate-based catalyst system to generate a range of synthetically useful structural features including tetrasubstitutedcarboncentres, and spiro- and bridged-ringcompounds, and in which 5-exo-trig cyclisations are kinetically favoured.