亞磷酸三苯酯和碘甲烷體系可以將醇轉(zhuǎn)化為相應(yīng)的碘代烴。亞磷酸三苯酯先和碘甲烷反應(yīng)得到甲基三苯氧基碘化鏻【碘化甲基（三苯氧基）鏻】，其能和醇進(jìn)行酯交換，發(fā)生苯酚的取代。鏻衍生物是一個(gè)好的離去基，能形成膦酸鹽。因此，碘化物進(jìn)攻磷酸鹽發(fā)生構(gòu)型轉(zhuǎn)換。

反應(yīng)機(jī)理

此反應(yīng)機(jī)理可以參考和，如下圖

反應(yīng)中亞磷酸酯是甲酯或乙酯，而此反應(yīng)利用苯酯，因此不能進(jìn)行上述反應(yīng)，但是亞磷酸三苯酯和碘甲烷反應(yīng)生成的甲基三苯氧基碘化鏻中間體，可以迅速和底物醇發(fā)生酯交換得到類似A的中間體, 然后發(fā)生類似的歷程發(fā)生構(gòu)型反轉(zhuǎn)，碘離子發(fā)生SN2取代得到碘代烴產(chǎn)物。

反應(yīng)實(shí)例

A 500-ml., two-necked, round-bottomed flask fittedwith a reflux condenser equipped with a calcium chloride drying tube is chargedwith 136 g. (115 ml., 0.439mole) of triphenyl phosphite, 35.2 g. (0.400 mole) of neopentylalcohol, and 85 g.(37 ml., 0.60 mole) of methyl iodide.A thermometer of sufficient length extends into the liquid contents of the flask. The mixture is heated under gentle reflux with an electric heatingmantle until the temperature of the refluxing liquid rises from its initialvalue of 75–80° to about 130°, and the mixture darkens and begins to fume. Thetime required is about 24 hours. It is necessary to adjust the heat input fromthe mantle from time to time as the reaction proceeds and the reflux ratediminishes. The reaction mixture is distilled under reduced pressure through a13-cm. Vigreux column. The fraction boiling below 65° (50 mm.) is collected and washed with 50 ml. of water,then with 50-ml. portions of cold 1 N sodiumhydroxide until the washings no longer contain phenol.The product is washed again with 50 ml. of water, dried over calciumchloride and redistilled, yielding 51–60 g. (64–75%) of neopentyl iodide, b.p. 54–55° (55 mm.), nD21 1.4882.

【 OrganicSyntheses, Coll. Vol. 6, p.830; Vol. 51, p.44】

A 500-ml., two-necked, round-bottomed flask fittedwith a reflux condenser equipped with a calcium chloride drying tube is chargedwith 124 g. (107 ml., 0.400mole) of triphenyl phosphite and 85 g.(37 ml., 0.60 mole) of methyl iodide.A thermometer of sufficient length extends into the liquid contents of theflask. The mixture is heated under gentle reflux with a heating mantle untilthe internal temperature has risen to about 120°. At this point the mixture isdark and viscous. The flask is cooled, and 40 g.(0.40 mole) of cyclohexanol is added to the oily methyltriphenoxyphosphoniumiodide. The mixture is shaken gently until homogeneous and allowedto stand overnight at room temperature. The mixture is distilled through a13-cm. Vigreux column, yielding 62.5–63 g.(74–75%) of iodocyclohexane, b.p. 66–68° (12 mm.), nD22 1.5475.

【Organic Syntheses, Coll. Vol. 6, p.830; Vol. 51, p.44】

To a solution of methyltriphenoxyphosphoniumiodide (2.3 mmol) in anhydrous dimethylformamide was added alcohol(2 mmol) at room temperature. Afterstirred for 18 h, the solvent was removed in vacuo and the residue wasdissolved in chloroform, extracted with 5% sodium thiosulfate, washed withwater and dried. Direct crystallizationfrom chloroform-hexane gave the iodide in 77% yield as needles.

【 J. A. C. S. 1964, 2093-2095】

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