Efficient access to Unsymmetrically 3-Substituted-1,10-Phenanthrolines via Microwave Assisted Friedländer Condensation with Aldehydes

An efficient method with high conversion percentages (70 – 100 %) for the exclusive synthesis of unsymmetrical 3-functionalised-1,10-phenanthrolines via microwave assisted Friedländer condensation is presented. The method was applied to alkyl and aryl aldehydes and aldehydes containing terminal p-methoxybenzyl (PMB) protected hydroxyl moieties. Deprotection of the terminal alcohol yields 3-alkyl hydroxy-1,10-phenanthrolines containing flexible alkyl linkers which have previously not been achieved. These functionalised compounds constitute key intermediates for the synthesis of flexible, unhindered 1,10-phenanthroline based systems into the future.