The Thermal Fragmentation of Some O-Arylsulfonyl Diphenylhydroxylamine Derivatives

Abstract

Thermal fragmentation of O-Aryl-N,N-diphenylhydroxylamines I and II were investigated. Neat heating in an atmospheric nitrogen afforded arenes, biaryl, diaryl sulfide, diphenylamine, diaryl sulfone, phenols, arenesulfonic acid, carbazole, and thianthrene. In the presence of isoquinoline as a radical trap, I gave 1-phenylisoquinoline as well as the previous products. Analogous results were obtained on heating of I in boiling tetraline, which lead to the formation of 1-hydroxytetraline, α -tetralone, and 1,1′-bitetralyl as the major products. A free-radical mechanism has been postulated to take place through the initial homolysis of N─O and S─O bonds to account for the identified products.

Keywords:

• Free radicals
• hydroxylamines
• thermolysis

Notes

^aH₂S was detected by chemical means; H₂O as a trace amount.

^bThe heating of I in the presence isoquinoline as a radical trap.

^cHeating of I in anhydrous boiling tetraline as aromatic solvent.

^dEstimated as BaSO₄.

^eBiphenyl.

^fp,p-Ditolyl.

^gPhenol.

^hp-Cresol.

ⁱDiphenyl sulfide.

^jp,p-Ditolyl sulfide.

^kDiphenyl sulfone.

^lp,p-Ditolyl sulfone.

^mBenzenesulfonic acid.

ⁿToluenesulfonic acid.

^oCollected at b.p. 113–116°C/6 Torr; n²⁰ _D: 1.5679; m/e 146.

^pCollected at b.p. 102–115°C/2 Torr as pale yellow oil; n²⁰ _D: 1.5638; phenyl. urethane derivative (ligroin), m.p. and m.m.p. 120–122°C; m/e 148.

^qEluted from column chromatography using a 2% mixture of ether-pentane, m.p. and m.m.p. 113°C; on heating with elemental sulfur give bis-naphthylene; ²⁶ m/e 262.