Electron-Transfer Reactions in Pulping Systems. 5. Application of an Intramolecular Cyclization Reaction as a Detector of the Formation of Quinonemethide Radical Anions

Article abstract of DOI:10.1021/jo00258a006

Compound 6, which incorporates a hex-5-enyl group on a quinonemethide precursor, has been synthesized and reacted in 1 M NaOH at 135 deg C in the presence of various pulping additives.Reduction of 6 either prior to or after cyclization to a five-membered ring provides evidence that a quinonemethide radical anion intermediate had formed.Some additives such as anthrahydroquinone and glucose were effective electron-transfer agents for the probe quinonemethide, while others such as sodium sulfide and sulfite were ineffective.The probe, therefore, provides information on the nature of chemical reactions that may be occurring during the pulping of wood.Anthrahydroquinone and glucose provided significantly different amounts of cyclized products.Glucose gave high yields of cyclized products, including three unique tricyclo<7.3.0.0^2,7>dodecatrienes.Apparently glucose reduces the radical intermediates relatively slowly, providing time for cyclization to occur.With no additives, other than 1 M NaOH, and long reaction times, the probe compound 6 provided some cyclized products; the electron-transfer agent in this case presumably is a phenolate ion.