Synthesis and acid–base properties of a proton-bridged biaryl compound based on pyridylazulene

Abstract

We report the synthesis and acid–base properties of 1,1′-bi(2-pyridylazulene) and the crystal structure of its mono-protonated form in which pyridyl moieties are interacted by an intramolecular hydrogen bond.

Stereochemistry, Stereodynamics, and Redox and Complexation Behaviors of 2,2′‐Diaryl‐1,1′‐Biazulenes

“…Both 1 and 2 adopted the syn ‐form with both aryl groups in the 2‐position, and the nearest face‐to‐face distances between intramolecular phenyl or pyridyl groups ranged from 3.36(1) to 3.39(1) Å for 1 and from 3.33(1) to 3.39(1) Å for 2 , which strongly suggests the presence of π‐π interactions . The dihedral angles between the azulene subunits (Az−Az) ranged from 48(1) to 53(1)° for 1 and from −51(1) to −52(1)° for 2 , while the dihedral angles between azulene and the aryl rings (Az−Ar) ranged from 33(1) to 46(1)° for 1 and from −32(1) to −45(1)° for 2 , which contrasts to the values obtained for the crystal structures of 2,2′‐bis(pyridine‐2‐yl)1,1′‐biazulene [Az−Az: 86(1)‐88(1)°, Az−Ar: 45(1)‐52(1)°], in which a proton acted as a bridge between the two pyridyl moieties …”

“…Meanwhile, optically active 2,2′‐dimethyl‐1,1′‐biazulene has been isolated . Furthermore, proton capturing behavior has been observed in the 1,1′‐biazulene bearing a 2‐pyridyl group; however, the dynamic behavior of 1,1′‐biazulene itself remains poorly understood, as do the substituent effects of its geometric structure and electronic properties.…”

Recent Advances in the Functionalization of Azulene Through Pd‐Catalyzed Cross‐Coupling Reactions

“…Ninomiya et al [81] . reported an 83 % yield of pyridylazulene 90 from the reaction of 2‐borylazulene 34 with the equivalent bromopyridine in the presence of Pd(OAc) 2 .…”

“…2,2′‐Di(pyridin‐2‐yl)‐1,1′‐biazulene ( 144 ) was obtained by borylation of 143 using bis(pinacolato)diboron pin 2 B 2 (52 %) (Scheme 53). [81] …”

Metal‐Catalyzed C−H Bond Activation of 5‐Membered Carbocyclic Rings: A Powerful Access to Azulene, Acenaphthylene and Fulvene Derivatives

“…Murafuji, Tsunashima et al. also employed this synthetic pathway in 2015 to prepare a 2‐(2‐pyridyl)azulene derivative; and very recently, Murai, Takai et al. also employed this methodology for the access to azulene‐fused linear polycyclic aromatic hydrocarbons with a small band gap…”