Synthesis, Characterization, and Functionalization of 1‐Boraphenalenes

Abstract

Abstract 1‐Boraphenalenes have been synthesized by reaction of BBr 3 with 1‐(aryl‐ethynyl)naphthalenes, 1‐ethynylnaphthalene, and 1‐(pent‐1‐yn‐1‐yl)naphthalene and they can be selectively functionalized at boron or carbon to form bench‐stable products. All of these 1‐boraphenalenes have LUMOs localized on the planar C 12 B core that are closely comparable in character to isoelectronic phenalenyl cations. In contrast to the comparable LUMOs, the aromatic stabilization of the C 5 B ring in 1‐boraphenalenes is dramatically lower than the C 6 rings in phenalenyl cations. This is due to the occupied orbitals of π symmetry being less delocalised in the 1‐boraphenalenes.