Chemiluminescence in Autoxidation of Phosphonate Carbanions. Phospha-1,2-dioxetanes as the Most Likely High-Energy Intermediates

Abstract

Autoxidation of the phosphonate carbanions derived from 9-phosphono-10-hydroacridanes provided chemiluminescence ascribed to the excited acridone anion. The intramolecular CIEEL (chemically initiated electron exchange luminescence) mechanism can be applied to this chemiluminescence because of the much higher emission efficiency compared to that of 9-phosphono-10-methylacridanes. The effect of the phosphonate substituents on the emission efficiency and especially on the rates of the chemiluminescence decay can be interpreted to originate from the valence deviation of the phosphorus atoms, which is connected with the substituent effect on the geometrical selectivity in the olefination reaction of the phosphonate carbanions. The enhanced chemiluminescence in the presence of the fluorophores was also detected in autoxidation of the carbanions of diethyl diphenylmethylphosphonate and fluorenylphosphonate. Although the evidence is circumstantial, these results strongly support the belief that phospha-1,2-dioxetane is the most likely high-energy intermediate generating the excited molecules.

Nef Reaction with Molecular Oxygen in the Absence of Metal Additives, and Mechanistic Insights

“…It is known that a single‐electron transfer (SET) process is involved in the auto‐oxidation of phosphonate carbanion with molecular oxygen31 and in the chemiluminescence reaction of imidazopyrazinone with molecular oxygen,32 therefore, the involvement of radical species in the present reaction was investigated by using radical clock techniques. We thus prepared a nitroalkane possessing a α‐cyclopropyl moiety.…”

Sterically Demanding Oxidative Amidation of α‐Substituted Malononitriles with Amines Using O2

“…First, we explored NO 2 , CN, SO 2 R, and PO(OR) 2 as suitable X/Y groups for the proposed oxidative amidation sequence (Figure c). These studies are summarized in Table .…”

Facile synthesis of 7-alkyl-1,2,3,4-tetrahydro-1,8-naphthyridines as arginine mimetics using a Horner–Wadsworth–Emmons-based approach

“…While the exact mechanism is not known, it may involve a reactive carbene intermediate formed by α-elimination of the phosphonate as described in previous reports [23]. Alternatively, a base-promoted autoxidation of phosphonate 7 in the presence of trace amounts of oxygen, followed by olefination may be taking place (Scheme 8) [24][25][26].…”