8‑Alkoxy- and 8‑Aryloxy-BODIPYs: Straightforward Fluorescent Tagging of Alcohols and Phenols

We demonstrate herein that both alcohols and phenols can be tagged with a BODIPY (borondipyrromethene) moiety to yield highly fluorescent products. Thus, 8-(methylthio)-BODIPY (<b>1</b>) undergoes an S_NAr-type reaction with a host of alcohols and phenols in the presence of a base and a Cu­(I) additive. The BODIPY dyes bearing alkoxy or nonfunctionalized phenoxy moieties are characterized by a highly efficient fluorescence emission, regardless of the media, in the blue-green part of the visible region. Complementary to this, the presence of electron-donor groups at the aryl ring leads to an intramolecular charge-transfer process, which quenches the fluorescence mainly in polar media. In addition to simple alcohols and phenols, four natural products (eugenol, menthol, cholesterol, and estrone) were labeled in a simple fashion. X-ray structures of the cholesterol and estrone derivatives are discussed. In fact, the BODIPY bearing cholesterol stands out as a bright fluorescence biological marker

Scope and Limitations of the Liebeskind–Srogl Cross-Coupling Reactions Involving the Biellmann BODIPY

Several new examples of <i>meso</i>-(het)­arylBODIPY were prepared via the Liebeskind–Srogl (L–S) cross-coupling reaction of the Biellmann BODIPYs (<b>1a</b>,<b>b</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 <i>meso</i> 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