A New Member of the BN-Phenanthrene Family: Understanding the Role of the BN Bond Position

3,4-Dihydro-4-aza-3-boraphenanthrene,
which shows the highest fluorescence
quantum yield of all nonsubstituted BN-phenanthrenes reported to date
(ϕF = 0.61), has been synthesized in only three steps
(76% overall yield) from easily accessible 1-bromo-2-vinylnaphthalene,
along with several substituted derivatives. The reactivity of these
previously unknown BN-aromatic compounds toward organolithium compounds
and bromine has been studied. This latter reaction affords bromo-substituted
compounds that are suitable for further functionalization via Suzuki
and Sonogashira couplings, with complete regioselectivity. The optical
properties and excited state deactivation mechanisms of selected compounds
were studied using computational methods.