Weak Base-Promoted Direct Cross-Coupling of Naphthalene-1,8-diaminato-substituted Arylboron Compounds

Abstract

The indispensability of a base in Suzuki–Miyaura coupling (SMC) employing organoboronic acids/esters is well recognized, which occasionally induces competitive protodeborylation in organoboron reagents. This phenomenon is particularly pronounced in fluorine-substituted aryl and heteroaryl boron compounds. Here, we show that direct SMC of naphthalene-1,8-diaminato (dan)-substituted aryl boron compounds, Ar–B(dan), characterized by its remarkable stability toward protodeborylation due to their diminished boron-Lewis acidity, occurs utilizing a weak base in conjunction with a palladium/copper cooperative catalyst system. The approach delineated in this study enables the efficient incorporation of various perfluoroaryl– and heteroaryl–B(dan) reagents, while maintaining high functional group tolerance. Furthermore, the inherent inertness of the B(dan) moiety allowed sequential cross-coupling, where other metallic moieties chemoselectively undergo the reaction, thus leading to the concise, protection-free synthesis of oligoarenes. Our results provide a potent approach to a delicate dilemma between a protodeborylation-resistant property and SMC activity intimately linked to boron-Lewis acidity.