High resolution NMR spectroscopy of heteroaromatic cations. II—pyrylium, thiapyrylium and seleninium cations

Abstract

High resolution 'H, proton coupled 13C and broad-band decoupled =C--(lH} spectra have been recorded for pyrylium, thiapyrylium and seleninium tetratluoroborates in CD3CN. Analysis of these spectra has provided accurate values and relative signs of all 'H,'H and 13C;H coupling constants, as well as the magnitudes of all one-and three-bond "C,'JC coupligs observable in naturally occurring doubly-labelled isotopomers. For the seleninium cation, the magnitudes and relative signs of all 77Se,'H and 77Se?C coupling constants were also obtained. The chemical shifts and coupling data are compared, on a qualitative basis, with existing theoretical predictions.

A Practical Synthesis of Thiopyrylium Tetrafluoroborate from Ethyl Vinyl Sulfide

“…A 13 C, 1 H‐COSY spectrum results in the 13 C assignment as laid down in Table 1. The 13 C NMR spectrum of 4a in CD 3 CN is identical to literature data 14,15…”

Air-oxidation of phenolic resin aerogels: backbone reorganization, formation of ring-fused pyrylium cations, and the effect on microporous carbons with enhanced surface areas

“…On the other hand, the new broad downeld resonances of TPOL-240(air) at 189.5 and 174.2 ppm were assigned to the ortho (a 0 and c 0 ) and para (f 0 ) carbons of the pyrylium ring, respectively. The meta carbons, d 0 and b 0 , were expected signicantly upeld, [42][43][44] and were assigned to the resonance at 97.9 ppm. Curiously, the only surviving Hs in TPOL-240(air) were those coming from T; that is, even the "e" carbon of as-prepared TPOL had lost its H, thereby fused-aromatic systems had to be head-to-tail connected to one another, as shown in Scheme 3.…”

Dicationic Heteroacenes Containing Thio- or Selenopyrylium Moieties

“…Although we could not detect 77 Se NMR resonance for 7b in CDCl 3 at room temperature, we observed a singlet for dication 1b at 727.1 ppm in CDCl 3 /CD 3 CN (v/v = 4:1) at room temperature (Figure S10). The resonance observed for 1b is low-field-shifted relative to neutral selenophene (δ = 613) and benzo­[ b ]­selenophene (δ = 526), as well as slightly upfield shifted relative to that of monocationic selenopyrylium derivatives, such as selenopyrylium perchlorate (δ = 976 in CF 3 COOD), selenopyrylium tetrafluoroborate (δ = 975.7 in CD 3 CN), and 3- tert -butyl-2-benzoselenopyrylium tetrafluoroborate (δ = 890 in CD 3 CN). The results of the 77 Se NMR analysis thus clearly suggest that 1b should be considered a cationic aromatic molecule.…”