A Short and Efficient Synthesis of the [3]Triangulene Ring System

Abstract

Triangulenes are of current interest for potential applications in molecular electronics. We describe here a three step synthesis of the 4,8,12‐trihydro[3]triangulenium cation by cascade cyclization of a tetra‐benzyl alcohol precursor in triflic acid solution. This stable carbocation is easily observed by NMR and optical spectroscopy and is highly fluorescent. Quenching of the cation into basic solutions or by hydride transfer from triethylsilane provides access to stable dihydro and tetrahydro[3]triangulenes. These neutral species interconvert with cations in a complex series of proton and hydride transfers. This route provides several important [3]triangulene precursors. Preliminary experiments designed to generate [3]triangulene in the solution phase provide evidence for its formation and rapid oligomerization.

Cascade Transformations of 1-R-Ethynyl-9,10-anthraquinones with Amidines: Expanding Access to Isoaporphinoid Alkaloids

“…The N-oxide 1 H and 13 C NMR peaks were shifted to the strong fields relative to the peaks of their analogs without the N-O bond. This suggests that the oxygen atom of the N-oxide moiety serves as an electron donor towards the acceptor N-heterocyclic moiety.…”

“…NMR spectra were recorded on a 'Bruker AV-400' 400.13 MHz ( 1 H) or DX-500 500.13 MHz ( 1 H) and 100.61 MHz ( 13 C) in CDCl3. 13 C spectra were recorded with complete suppression of the 13 C-1 H spin-spin interaction on a pulsed J-modulation program. Mass spectra were obtained on a Finnigan SSQ-710 mass-spectrometer by the direct injection method (the temperature of the ionization chamber was 220-270 • C, the ionization voltage, 70 eV).…”

“…1 H NMR (CDCl 3 , 500 MHz) δ 2.55 (s, 3H, -CH 3 ), 7.29-7.34 (m, 3H, H-5, H m ), 7.72-7.75 (m, 5H, H m', H o', H p' ), 7.81 (d, 2H, H o, J = 10), 7.87 (t, 1H, J = 10, H-10), 7.93 (t, 1H, J = 10 Hz, H-9), 8.14 (d, 1H, J = 10 Hz, H-4), 8.47 (d, 1H, J = 10 Hz, H-6), 8.72 (d, 1H, J = 10 Hz, H-8), 9.09 (d, 1H, J = 10 Hz, H-11). 13 The yield of 2-benzo-3-hexanoyl-7H-dibenzo[de,h]quinolin-7-one 2e was 57%, time of reaction 3 h, m.p. 178.5-179 • C (from hexane).…”

“…1 H NMR (CDCl 3 , 400 MHz) δ 0.78 (t, 3H, -CH 3 ), 1.04-1.16 (m, 4H, -CH 2 -CH 2 -Me), 1.53 (t, 2H, -CH 2 -Pr), 2.37 (t, 2H, -CH 2 -Bu), 7.52-7.57 (m, 3H, H-5, H m' ), 7.69 (t, 1H, J = 8 Hz, H-10), 7.81-7.85 (m, 3H, H o' , H p' ), 7.96 (t, 1H, J = 8 Hz, H-9), 8.21 (d, 1H, J = 8 Hz, H-4), 8.44 (d, 1H, J = 8 Hz, H-6), 8.69 (d, 1H, J = 8 Hz, H-8), 9.04 (d, 1H, J = 8 Hz, H, H-11). 13 C NMR (CDCl 3 , 100 MHz) δ 13.9, 22.3, 23.9, 31.17…”

Twofold π-Extension of Polyarenes via Double and Triple Radical Alkyne peri-Annulations: Radical Cascades Converging on the Same Aromatic Core

“…[32][33][34][35][36][37][38][39][40][41][42][43][44][45] Yet, most of the available examples of alkynes being used in the preparation of these carbon-rich molecules concentrate on extension at the armchair edge of the polycyclic framework, while alkyne annulations at the zigzag edge remain remarkably scarce (Scheme 1). 46,47 Scheme 1. Left: peri-annulations allow benzannulations at the zigzag edge of polyarenes.…”