Functionalization of 3,5,8-Trichlorinated BODIPY Dyes

ABSTRACT: Catalytic hydrogenation of dibenzyl 5-dipyrro-ketone-2,9-dicarboxylates followed by decarboxylative iodina-tion affords a 2,9-diiododipyrroketone which gives a 2,5,9-trichlorodipyrromethene hydrochloride after nucleophilic addition/elimination, with adventitious chloride to replace the two iodide groups. Treatment with BF3·Et2O gives a 3,5,8-trichloro-BODIPY that readily undergoes regioselective Stille coupling at the 8-position, or homo/mixed couplings at the 3,8- or 3,5- and 8-positions. Stepwise and controlled replacement of the 3,5- and 8-chlorine atoms using Stille reagents results in formation of a completely unsymmetrical trisubstituted BODIPY. Several examples of unsymmetrical BODIPYs were synthesized and characterized using this methodology. Structure features of new BODIPYs are discussed within the context of 14 new X-ray structures, and photophysical parameters of all new BODIPY compounds are reported and discussed. 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (known as BODI-PY) is a class of very versatile fluorophores that has been widel