Phosphine tertiary degradation

Preparation of quaternary phosphonium salts is of great importance as it leads to the phosphorus ylides that are needed for Wittig olefination (see page 996). Further, quaternary phosphonium salts are intermediates in the methods of preparation of unsymmetrical phosphines that depend on successive alkylation of tertiary phosphines and degradation of the resulting quaternary salts. Three processes have been developed for the last-mentioned reaction ... 

Phosphonium salts are typically stable crystalline soHds that have high water solubiUty. Uses include biocides, flame retardants, the phase-transfer catalysts (98). Although their thermal stabiUty is quite high, tertiary phosphines can be obtained from pyrolysis of quaternary phosphonium haUdes. The hydroxides undergo thermal degradation to phosphine oxides as follows ... 

Complete degradation of organocopper aggregates may occur when they react with tertiary phosphines. This is illustrated by treatment of arylcopper compounds with bis-(diphenylphosphino)methane (DPPM) and with l,2-bis-(diphenylphosphino)-ethane (DPPE) (see Scheme 1.11). 

Emerald green crystals of rrans-[RhCl2(PR3)2] can be obtained from the tertiary phosphine and hydrated rhodium trichloride at room temperature. The NMR spectrum is degraded and multiple peaks from vRh. c, in the far IR spectrum suggest that the product is a trans rhodium(II) complex.272... 

Oxidative free-radical degradation by hydroperoxides can be catalyzed by certain transition metal ions, especially those of copper, cobalt, and manganese. To reduce the rate of free radical formation, two classes of additives are used (1) organic phosphines, amines, and sulfides which catalyze the decomposition of the hydroperoxides to noiuadical products, and (2) metal-ion chelators (e.g., Ph-CH=NNH-CO-CO-NHN=CH-Ph). Tertiary phosphines are thus oxidized to phosphine oxides, tertiary amines to amine oxides, and sulfides to sulfoxides, e.g.,... 

A) are combined in a reactor and heated for a couple of hours. The reaction is carried out at the temperature range of 140-180 °C under a nitrogen blanket to minimize oxidative degradative reactions. In the reaction, known catalysts such as tertiary amines or phosphines, quaternary ammonium or phosphonium salts, and imidazoles are applied [118]. 

In conclusion, we have presented a new method for the preparation of tertiary phosphine oxides of the type R2R P0 from a secondary phosphine oxide and an alkyl halide with excellent yields, using phase transfer catalysis. Furthermore, this method can be successfully applied to the chemical modification of soluble and cross-linked polystyrenes. Examination of the molecular weights, M, and of the composition of the modified polymers indicates that no side reactions or degradation occur in the conditions we have used. Further work in this field is in progress. 

The tertiary phosphines also abstract sulfur atoms from numerous compounds to form phosphines sulfides. Thus triphenylphosphine will degrade a dialkylpolysulfide (Moore and Saville, 1954). Schoberl (1935 Schoberl and Barakat, 1949) has treated various sulfides with triphenylphosphine in benzene. 

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