Three-, Four-, and Five-membered-ring Phosphoranes

5 Three-, Four-, and Five-membered-ring Phosphoranes 

Monocyclic Systems.—Treatment of the betaine (50) with hydrogen peroxide at 0 °C gave phenyl diphenylphosphinate (68) triphenylphosphine dioxide (67), formed via (66), was suggested as the critical intermediate. Evidence for the formation of a bisperoxyphosphorane, Ph3P(OOBu )2 [8( P) = —42.3 p.p.m.], is presented in the same paper. 

In contrast to an earlier report, treatment of (69) with alkyl-lithium in salt-free THF at —78 °C did not give any detectable (by n.m.r.) quantities of either (70) or (71), although a red colour was observed which could have been due to a low concentration of the ylid. 

The chlorination of (72) at —100 °C gives the trichlorophosphorane (73), which rearranges above — 40 °C to the dichlorophosphate (74) with no evidence for the formation of the phosphonium salt (75). Likewise, the halogenation of (76a,b) at low temperature gives the phosphoranes (77a,b) which, with the exception of (77b, X = Br), are stable at room temperature. The latter compound, which was shown to be in equilibrium with the phosphonium salt (78), slowly gave a spirophosphorane (79) by cleavage of the ether linkage. The 

A series of cyclic phosphoranes (86) has been obtained by the reaction of the bicyclic peroxide (84) with three-co-ordinate phosphorus compounds (85) and the products characterized by and n.m.r. The increasing ring 

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