P,O-Heterocyclics

P,O-Heterocycles, formation in reactions of P(I1I) chlorides with oxygen-containing reagents 90MI5, 90UK431. 

X-ray crystal structure determinations have been carried out on a limited number of P/O heterocycles. 10-Phenylphenoxaphosphine (265) was confirmed to be nonplanar by this method the molecule is folded along the P" 0 axis, and the phosphorus atom is nonplanar <76JCS(P2)1383>. The cation of 2,4,4,6-tetraphenyl-1,4-oxaphosphininium perchlorate (266) is described as quasi-planar, although a small degree of folding is evident <74CSC227>. 

In contrast, multifarious uses have been proposed for P-O heterocyclic systems. It is convenient to divide them into biological and medicinal uses, and others. 

Cycloaddition of hexafluoroacetone to iminophosphine resulted in the only example of a three-membered P,O-heterocycle 1 known till now (Scheme 1) [9],... 

Four-membered P.O-heterocycles 31 were obtained from [2 + 2]-cycloaddition of carbonyl compounds to phosphorylated carbenes generated from a-diazabenzyl-phosphine oxide under thermal- or photoinitiation (Scheme 16) [32-34], 2-Oxo-l,2-... 

P.O.67 is a member of the pyrazolo-quinazolone pigment series. Its constitution is listed in the Colour Index under Constitution No. 12915. Coupling component is the heterocycle shown on p. 503. The diazonium component is 2-nitro-4-chloroani-line. Coupling affords the pigment, which was found to exhibit the hydrazone structure ... 

Reaction 5. Several kinds of decomposition of C H2 OOH to a product (or products) + OH are possible. For simplicity, these calculations have been performed only for the case in which a single product P is formed, and that is an O-heterocycle. This mode of decomposition is a major one, particularly at temperatures characteristic of cool flames (3, 19, 20, 24, 45). 

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