Synthesis of 1,8-Bis(chloro(mesityl)boryl)-naphthalene and 5,6-Bis(chloro(mesityl)boryl)-1,2-dihydroacenaphthene and Their Reactivity with the Wittig Reagent, Methylenetriphenylphosphorane

The naphthalen-1,8-diyl and dihydroacenaphthen-5,6-diyl platforms have been widely utilized as rigid aromatic scaffolds to support a myriad of p-block elements. This is especially true for boron, where several 1,8-diboryl naphthalene derivatives have been reported. Of the many diboryl compounds in the scientific literature, 1,8-bis(halo(aryl)boryl) and 5,6-bis(halo(aryl)boryl) naphthalenes and dihydroacenapthenes are unknown, which prompted the work described herein. Here, we report on the synthesis and full characterization, including multinuclear NMR spectroscopy and single-crystal X-ray diffraction, of 1,8-bis(chloro(mesityl)boryl)-naphthalene and 5,6-bis(chloro(mesityl)boryl)-1,2-dihydro-acenaphthene, compounds 1 and 2, respectively. We have also explored the chemistry of 1 and 2 with methylene triphenylphosphorane to afford two novel 1,1-diboryl phosphorus ylides, 3 and 4, which have also been fully characterized. The structure and bonding in these diboryl ylides were further interrogated using computational methods.