Introducing the Dihydro-1,3-azaboroles: Convenient Entry by a Three-Component Reaction, Synthetic and Photophysical Application

The (Fmes)­BH2·SMe2 reagent (7) reacts sequentially
with an acetylene and, e.g., xylylisonitrile
in a convenient three-component reaction to give a series of unprecedented
dihydro-1,3-azaborole derivatives 16. The tolane-derived
example 16a was deprotonated and used as a ligand in
organometallic chemistry. Compounds 16 served as the
starting materials for the straightforward synthesis of various dihydro-1,3-azaborinine
derivatives by treatment with an isonitrile. Several diaryldihydro-1,3-azaboroles
showed interesting photophysical properties such as aggregation-induced
emission and high fluorescence quantum yields.