title: DOTTADs--readily made novel metal ligands with multivariant functionality--trans-DOTTADs and semi-DOTTADs.
abstract: Two new ligand systems related to the previously described DOTTADs have been generated in a simple one step reaction. The first, trans-DOTTADs, were formed by Vilsmeier formylation (followed by cyclisation and N-demethylation) of 2,6-dimethyl-3,5-pyrazine-dicarboxylic acid, to give the novel bis-pyridinopyrazine dialdehyde ligands. The corresponding pyrazine diester, reacted similarly to an intermediate iminium ion stage, which gave trans-DOTTAD imines on work-up with amines. The treatment of Hantzsch ester with two equivalents of benzaldehyde gave 7-phenyl-2-(2-phenylethenyl)-7,8-dihydropyrano[4,3-b]pyridin-5-one-3-carboxylic acid. This product underwent similar cyclisation with Vilsmeier reagents to give, for example, 6-methyl-2-(2-phenylethenyl)-8-(phenylhydroxymethyl)-6H-[1,6]naphthyridin-5-one-3-carboxylic acid, an example of a semi-DOTTAD.
authors.affiliation: Institute of Pharmacy, Chemistry and Biomedical Sciences, University of Sunderland, Wharncliffe Street, Sunderland, UK SR1 3SD.
authors.forename: Andrea
authors.initials: A
authors.lastname: Arany
authors.forename: Otto
authors.initials: O
authors.lastname: Meth-Cohn
authors.forename: István
authors.initials: I
authors.lastname: Berhés
authors.forename: Miklós
authors.initials: M
authors.lastname: Nyerges