Oxidation of allenes bearing 1,8‐diphenoxy or diaryloxyacridene moieties

Abstract

New allene compounds bearing 1,8‐diphenoxy or bis(3,5‐di‐tert‐butylphenyl) oxyacridene (diaryloxyacridene) moieties were synthesized. These compounds were more easily oxidized than Cl‐substituted compounds. The allene compounds were oxidized to generate thermally stable triplet carbenes. Electron spin resonance and electron spin transient nutation spectra of the oxidation reaction products suggested the generation of triplet species; however, the main isolated product from the 1,8‐diphenoxy allene was a cyclized compound that was characterized by X‐ray analysis. The product derived from diaryloxy allene was also characterized by X‐ray analysis as a singlet species, which included a vinyl cation stabilized by a neighboring O(3,5‐di‐tert‐butylphenyl) group. This singlet species was stable even at room temperature and did not show any electron spin resonance signals in solution, indicating that the triplet species was not in equilibrium with the singlet. Copyright © 2016 John Wiley & Sons, Ltd.

Preface for the special issue of ISRIUM‐2015 in Honolulu, Hawaii, USA

“…Oxidations of allenes bearing 1,8‐diphenoxy or diaryloxyacridene moieties are performed by the research group of Professor Yohsuke Yamamoto to generate persistent triplet carbenes. They isolate a cyclized compound that is characterized by X‐ray analysis.…”

“…They isolate a cyclized compound that is characterized by X-ray analysis. [2] The research group of Professor Wolfram Sander reports the generation of a new sextet ground-state molecule, the 2,4,6trichloro-1,3-dinitrenophenoxyl radical, in the UV photolysis of the corresponding diazido precursor in argon at 5 K. [3] They found that the sextet molecule is formed in a stepwise fashion, with the triplet nitrene, the quartet nitreno radical, and the quintet dinitrene as intermediates that are detected by electron paramagnetic resonance spectroscopy.…”