Theoretical Studies On The Hydrolysis And Aminolysis Of Phosphorus Heterocyclic

With the rapid development of phosphorus heterocyclic chemistry during the past fifty years, there have been several dissertations in this field. In this paper, we studied two kinds of phosphorus heterocycle. One is triphenyl phosphite ozonide, the other is 3-(4-nitrophenylsulfonyl)-2-phenyl-2-thioxo-1,3,2-oxazaphospholidine.The decomposition of triphenyl phosphite ozonide (TPPO) has been well recognized as a potential source of singlet oxygen (O₂ , ¹Î”_g) for the chemical oxygen-iodine laser. Experimental observations suggested that ammonia or pyridine water solution can accelerate the decomposition of TPPO, and hydroxyl ion is responsible for accelerating singlet oxygen liberation during this decomposition. This"catalyst"is more efficient than pyridine-methanol mixture and pyridine-ethanol mixture. In this paper, we studied the mechanism of OH^--accelerated and CH₃O^--accelerated reaction using density functional theory (DFT) at B3LYP/6-31+G^* levels of theory. The accelerated decomposition of TPPO proceeds firstly via nucleophilic attack of the phosphorus atom on the ozonide by OH^- or CH₃O^- from the"catalyst"system. There are two possible pathways following the formation of the stable intermediate, that is, pathway a and b. The calculated relative free energies indicated that pathway a was kinetically more favorable than pathway b, namely, elimination of PhO^- and subsequent liberation of singlet oxygen was more favorable than liberation of singlet oxygen at first and subsequent elimination of PhO^-or PhOH. Qualitative argumentations were presented from a frontier molecular orbital description to account for the thermal instability of the ozonides. These ozonides readily decompose mainly because there is little bonding interaction existed in the ozonide ring. To allow for a quantitative comparison between the bonding, a kind of bond order index—the Wiberg bond index (WBI) was calculated. The substitution of phenoxy group in TPPO by OH^- or CH₃O^- led to a decrease in one of the P-O WBI bond orders.It is generally noted that hydrolysis or alcoholysis of phosphorus heterocycles are favoured over aminolysis. The compound 3-(4-nitrophenylsulfonyl)-2-phenyl-2-thioxo-1,3,2-oxazaphospholidine, in contrast to all other phosphorus heterocycles studied so far, reacted easily with amines, sometimes selectively in the presence of water, leading to the corresponding amides. In this paper, we studied the mechanism for hydrolysis, alcoholysis and aminolysis of 3-(4-nitrophenylsulfonyl)-2-phenyl-2-thioxo-1,3,2-oxazaphospholidine using density functional theory (DFT) at B3LYP/6-31+G^* levels of theory.