Palladium-Catalyzed Cross-Coupling Reactions of 4a,8a-Azaboranaphthalene

Abstract

A concise and effective three-step synthesis of 4a,8a-azaboranaphthalene (ABN) has been developed in gram scale. Electrophilic aromatic substitution reactions of ABN provide excellent functional-group-tolerant cross-coupling partners in various Pd-catalyzed cross-coupling reactions (e.g., Sonogashira, Suzuki-Miyaura, or Heck reaction). Photophysical, electrochemical, and DFT calculations all suggest a narrowed HOMO-LUMO gap with extended π-conjugation characters in the cross-coupled molecules. The ABN moiety as a new fluorophore has a distinct and selective fluorescence response toward Zn(II) and Cd(II) ions, demonstrating great potential for the ABN structural motif in fluorescent chemosensors.

Negishi Cross-Coupling Is Compatible with a Reactive B–Cl Bond: Development of a Versatile Late-Stage Functionalization of 1,2-Azaborines and Its Application to the Synthesis of New BN Isosteres of Naphthalene and Indenyl

“…13 This achievement should allow selective late-stage functionalization at C3 via cross-coupling technologies. Although not specifically demonstrated on a monocyclic 1,2-azaborine, Molander 14 and Fang 15 showed that a variety of cross-coupling methods, including Suzuki, Kumada, Sonogashira, and Heck reactions, can be performed on halogenated BN-naphthalenes.…”

Regioselective Functionalization of Stable BN‐Modified Luminescent Tetraphenes for High‐Resolution Fingerprint Imaging

“…[1] One appealing approach is the replacement of one or more C = Cbonds in PA Hs by isosteric BN pairs,which may significantly modify the chemical and electronic properties of the molecule due to the polarization of the B À Nbond while maintaining the aromaticity and basic structural features of the original compounds. [6] Thepotential of this strategy in extending the p conjugation and modulating the optical and electronic properties or other functional properties of am olecule has not been fully investigated yet.As mentioned above,m ost boron-containing compounds are air-a nd moisture-sensitive due to the inherent electron deficiencyo ft he boron atom. However,the real applications of the materials still remain an unknown proposition, because their stability and sensitivity to ambient conditions are important.…”

“…[2][3][4] Indeed, this strategy has enriched the family of PA Hs with modulated properties. [6] Thepotential of this strategy in extending the p conjugation and modulating the optical and electronic properties or other functional properties of am olecule has not been fully investigated yet. Moreover,a nother primary reason is the lack of available synthetic routes to produce large amounts of these materials.T oour knowledge, so far, the synthetic strategies are quite limited and they usually rely on classical electrophilic borylations performed under harsh conditions.T herefore,s uitable methodology is needed to enrich the chemical diversity of BN-containing compounds,which not only provides the possibility to explore the performance of these materials in device applications,but also renders the opportunity to systematically study their structure-property relationships.T he selective late-stage functionalization is the most general and efficient approach to achieve chemical diversification and to fine-tune the molecular properties of functional molecules.…”

“…[5] However, little attention has been paid to applying this approach to BNdoped aromatic compounds,e specially BN-modified conjugated molecules. [6] Thepotential of this strategy in extending the p conjugation and modulating the optical and electronic properties or other functional properties of am olecule has not been fully investigated yet.As mentioned above,m ost boron-containing compounds are air-a nd moisture-sensitive due to the inherent electron deficiencyo ft he boron atom. Therefore,n ew strategies are quite beneficial to stabilize the boron center.T he most common strategy is to use sterically bulky groups to kinetically stabilize the boron center, [7] but this is at the expense of preventing solid-state p-p stacking.I nr esponse to these limitations,a ne xciting concept for stabilizing organoboron compounds was introduced by Yamaguchi and Piers,w ho demonstrated that enforced planarity could stabilize boroncontaining p-conjugated materials.…”

“…[5] However, little attention has been paid to applying this approach to BNdoped aromatic compounds,e specially BN-modified conjugated molecules. [6] Thepotential of this strategy in extending the p conjugation and modulating the optical and electronic properties or other functional properties of am olecule has not been fully investigated yet.…”