Pd(0)-catalyzed amination in the synthesis of bicyclic compounds comprising triazacycloalkane and fluorophore moieties

Direct introduction of one dansyl fluorophore group into the molecule of 1,4,7-triazacyclononane (TACN) and 1,5,9-triazacyclododecane (TACD) was shown to be possible followed by the modification of triazacycles with two bromobenzyl substituents. The resulting compounds were used in the Pd(0)-catalyzed macrocyclization reaction with 1,13-diaza-4,7,10-trioxatridecane to provide corresponding cryptands. The synthesis of bicyclic derivatives of TACN bearing naphthyl and acridinyl fluorophore groups was accomplished via an alternative procedure using aminal-protected TACN. The possibility to form tetracyclic compounds starting from N,N’,N”-tris(3-bromobenzyl) substituted TACN was demonstrated. Three cryptands bearing dansyl fluorophore were tested as potential fluorescent chemosensors for metal cations and were found to act as molecular fluorescent probes for Cu(II) and Al(III) by total emission quenching in the presence of these cations.