Fully unsubstituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) 1 was prepared. Reaction of 8-thiomethylbodipy 2 with triethylsilane in the presence of a catalytic amount of Pd and a stoichiometric amount of copper(I) thienyl-2-carboxylate (CuTC) in THF at 55 degrees C gave compound 1 in nearly quantitative yield. This compound displays high quantum yields (up to 93%) in polar solvents including water. Its optical properties and crystal structure are discussed.

A new series of 8-alkenylBODIPY dyes were prepared via the LiebeskindeSrogl cross-coupling starting from 8-thiomethyl-substituted BODIPY. Ten derivatives were prepared using alkenylboronic acids in good to excellent yields (79e97%), and one additional example was prepared from an alkenylstannane in 74% yield. The products display Michael acceptor-like reactivity. The alkenyl fragment quenches the fluorescence of the BODIPY core, which is turned back on by reducing the double bond.

Several new examples of meso-(het)arylBODIPY were prepared via the Liebeskind-Srogl (L-S) cross-coupling reaction of the Biellmann BODIPYs (1a,b) and aryl- and heteroarylboronic acids in good to excellent yield. It was shown that this reaction could be carried out under microwave heating to shorten reaction times and/or increase the yield. It was illustrated that organostannanes also participate in the L-S reaction to give the corresponding BODIPY analogues in short reaction times and also with good to excellent yields. We analyze the role of the substituent at the sensitive meso position in the photophysical signatures of these compounds. In particular, the rotational motion of the aryl ring and the electron donor ability of the anchored moieties rule the nonradiative pathways and, hence, have a deep impact in the fluorescence efficiency.

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