Biphilic insertion reactions

Recently, this reaction was extended to include triphenylarsine and triphenyl-antimony.The fact that the relative reactivity was PhsP PhaSb >PhaAs confirms that the mechanism involves biphilic insertion into the peroxide bond rather than nucleophilic displacement, leading first to the pentacovalent intermediate. 

Further evidence for a biphilic insertion mechanism is derived from a study of the reaction of the bicyclic phosphoramidites (115) and (116) with diethyl peroxide to form (117) and (118), respectively. The strained 1-phosphabi-cyclo[3.3.0]octane (115) reacts much faster than its l-phosphabicyclo[4.4.0]-decane analogue (116), but the opposite reactivity is found towards diphenyl disulphide. At room temperature (116) produced (120) within seconds, presumably via an intermediate phosphonium salt, whereas (115) gave (119) [S 3ip = —19 p.p.m.] after 1 h at 58 °C. As mentioned earlier, the latter appears to be the only phosphorane reported so far with two exocyclic P-S bonds. 

Nucleophilic Attack on Oxygen or Sulphur.— The reactions of two bicyclic phosphoramidites, (35) and (36), with diethyl peroxide or diphenyl disulphide have been studied. Based on ring-strain arguments, the higher rate of (35) with diethyl peroxide, and of (36) with diphenyl disulphide, is considered support for a biphilic insertion mechanism for the addition of diethyl peroxide, and an... 

The failure to observe any radical products 7 or acetone) in the decomposition of 6 allows us to rule out a mec Hanism for the anchimerically accelerated homolysis of 3 which begins with a biphilic insertion of sulfenyl sulfur into the 0-0 bond of 3 to yield 6 directly with 6 serving as the precursor to radical products. "Analogous bipliilic insertion reactions have been used to produce sulfuranes from the reaction between sulfoxylates and dioxetanes (18). 

Diethyl disulfide is inserted by phenylphosphene (74), apparently involving a biphilic reaction. 

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