PhO) 3 P [101-02-0] C 18 H 15 O 3 P (MW 310.30) InChI = 1/C18H15O3P/c1--15H InChIKey = HVLLSGMXQDNUAL-UHFFFAOYAF (mildly nucleophilic phosphite for converting alcohols to alkyl halides; 3 coupling agent in peptide and related syntheses, 1b,12 as its ozone adduct, a low-temperature source of singlet oxygen 1b ) Physical Data: mp 22-25 • C; bp 360 • C, 180-189 • C/1 mmHg; n 25 D 1.5890; δ 31 P 125-129. Solubility: insol H 2 O (hydrolyzes to (PhO) 2 P(O)H); miscible most organic solvents; alcoholic solvents may transesterify. Form Supplied in: colorless liquid, 97% pure, widely available, showing only one peak in 31 P NMR. The balance is largely phenol. Purification: an ethereal solution is washed with aqueous alkali, dried, and distilled. Handling, Storage, and Precautions: fairly safe to handle, but itis a skin sensitizer and will usually contain phenol.General Discussion. The ester converts alcohols to alkyl halides in the presence of a hydrogen halide, a halogen, or another alkyl halide (eqs 1 and 2), the two last being mild and convenient procedures. 2,3 Good yields are obtained, even with neopentyl halides, and the reaction proceeds with inversion at carbon. 4 The intermediate phosphonium salts may be prepared independently but are very susceptible to hydrolysis and are conveniently generated and used as required. Methyltriphenoxyphosphonium iodide has also found use in the deoxygenation of epoxides 5 (with retention of stereochemistry) and the dehydration of secondary alcohols. 6 Phenyl esters of carboxylic acids can be made from the salts and a carboxylate ion 7 or from the free acid and the neutral ester 8 (eqs 3 and 4). Phosphorus 9 and sulfur 10 acids may be esterified similarly.