DOTTADs — readily made novel metal ligands with multivariant functionality and chirality

A variety of novel ligands have been generated by Vilsmeier formylation of Hantzsch pyridines. These compounds which we call DOTTADs contain two aldehyde, imine or amine functions flanking a central pyridine nitrogen and can be homochiral or crown derivatives. The synthesis and manipulation of these systems is discussed. © 2000 Elsevier Science Ltd. All rights reserved. Some years ago we described1 a new cyclisation whereby ortho-methylarenecarboxylic acids (e.g. 1) in which the methyl group was ‘activated’, underwent diformylation at the methyl group with a Vilsmeier reagent (Me2N_CHCl X ) followed by intramolecular acylation at the introduced nitrogen and subsequent demethylation to generate a fused pyridone-aldehyde (e.g. 2, Scheme 1). This reaction proved quite general, the activation being effected by a conjugated nitro-group, a pyridine ring nitrogen or even an -carboxylic acid group (e.g. homophthalic acid). Scheme 1. In this paper we show that the reaction is a highly efficient and versatile route to very useful ligands with novel potential. Thus, the compounds 2 and their congeners are themselves effective ligands for group I metals (possibly by use of the ring N and the aldehyde-hydrate). We have focused in particular on the readily available Hantzsch pyridinecarboxylic acids 6. Formylation results in bis-cyclisation to generate a novel system 4 (Table 3) which also shows a number of interesting variants, and the products Corresponding author. E-mail: [email protected] (O. Meth-Cohn) 0040-4039/00/$ see front matter © 2000 Elsevier Science Ltd. All rights reserved. P I I: S0040-4039(99)02243-1