The Cobalt-Way to Heterophenylenes: Syntheses of 2-Thianorbiphenylenes, Monoazabiphenylenes, and Linear 1-Aza[3]phenylene {Biphenyleno[2,3-a]cyclobuta[1,2-b]pyridine}

Abstract

Supporting Information General Methods. Unless otherwise stated, all starting materials were purchased from commercial suppliers and used without further purification. THF was freshly distilled from sodium benzophenone ketyl; toluene, diisopropylamine, and (trimethylsilyl)acetylene were distilled from CaH 2 ; bis(trimethylsilyl)acetylene and CpCo(CO) 2 were vacuum transferred immediately before use. All reactions involving airor moisture-sensitive materials were carried out under an atmosphere of dry nitrogen or argon with oven-or flame-dried glassware. In experiments requiring slow addition of reagents, NORM-JECT single-use syringes were used, mounted on a Sage Instruments single syringe pump. The light source used in cycloaddition reactions employing CpCo(CO) 2 was a 300 W tungsten halogen slide projector lamp with an applied potential of 60-70 V positioned 3-5 cm from the flask. Analytical thin-layer chromatography (TLC) was performed on Merck silica gel 60 F254 plates. Flash chromatography was executed on silica gel (60-200 or 230-400 mesh) from Sorbent Technologies, preparative thin-layer chromatography on silica gel GF Uniplates (UV254, 1000 microns) from Analtech. NMR spectra were recorded on Bruker AVQ400 (400 MHz), AV500 (500 MHz), or AV600 (600 MHz) instruments. Multiplicity is described by the abbreviations s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet. Chemical shifts are given in ppm. 1 H NMR spectra were referenced to the residual solvent peaks at δ = 7.26 (CDCl 3) or 5.32 ppm (CD 2 Cl 2). 13 C NMR spectra were referenced to the solvent peaks at δ = 77.0 (CDCl 3), 54.0 (CD 2 Cl 2), and 128.39 ppm (benzene). Infrared spectra were obtained on Thermo Nicolet, Avatar 370, or Perkin Elmer Spectrum 100 FT-IR spectrometers, respectively, and are reported in wavenumbers (cm-1). UV/Vis spectra were obtained on either a Hewlett-Packard HP 8453 UV-Vis ChemStation, a Perkin Elmer Lambda 35 spectrometer, or a Varian 50 Bio UV/Vis

Tetraazaacenes Containing Four-Membered Rings in Different Oxidation States. Are They Aromatic? A Computational Study

“…Also, Swager et al have prepared some related acenocyclobutadienes and analyzed their properties and potential applications . However, there are only very few reported cases (Hünig, 1 , and Vollhardt, 2 ) , in which pyridines or pyrazines are juxtaposed to cyclobutadiene units, such as 3 (Figure ) …”