Palladium-Catalyzed Ullmann Cross-Coupling Reactions for the Synthesis of Heterocyclic Compounds

Abstract

Publication 1 is an invited review article that details the development of the palladium-catalyzed Ullmann cross-coupling reaction within the Banwell Group. Specifically, it describes the extensive effort directed towards modernizing the Ullmann reaction so as to circumvent the harsh conditions associated with the classic protocol. The reductive cyclisation of ensuing cross-coupling products is also

Publication 2 describes work directed towards engaging beta-iodinated alpha,beta- unsaturated carbonyl compounds in the palladium-catalyzed Ullmann cross-coupling with o-halonitroarenes as well as the less reactive o-halobenzonitriles. The reductive cyclisation of the products of such reactions allows access to various heterocyclic frameworks including benzomorphans that, hitherto, had been inaccessible via such pathways.

Publication 3 details methods for the reductive cyclisation of o-nitroarylated alpha,beta- unsaturated carbonyl compounds arising from the palladium-catalyzed Ullmann cross-coupling reaction. Specifically, complementary modes of reductive cyclisation are observed on using titanium trichloride/HCl or iron/HCl and so allow for different heterocyclic systems to be obtained from the same substrate (by varying the nature of the reducing system that is employed). Such processes significantly enhance the utility of products available through the palladium-catalyzed Ullmann cross-coupling reaction.

Publication 4 describes a protocol related to the palladium-catalyzed Ullmann cross-coupling reaction for the one-pot synthesis of functionalized benzofurans, indoles and phthalanes. Specifically, it details a tandem Ullmann-Goldberg cross coupling/cyclopalladation-reductive elimination reaction involving iodophenols or iodoanilines and beta-halogenated alpha,beta-unsaturated carbonyl compounds. The overall process involves exposure of the substrates to a combination of Cu[I]- and Pd[0]-catalysts