Diethyl triphenylphosphonium bromide

Reaction of 4-aryl-7-iodoperhydropyrido]2,l-c][l,4]oxazin-6-ones (07USA2007/0117839, 08WOP2008/013213) and 7-iodo-6-oxo-4-(3,4,5-tri-fluorophenyl)perhydropyrido[2,l-a]pyrazine-2-carboxylate (07USA2007/ 0117839) with P(OEt)3 at 120 °C for 2 h afforded 7-phosphonic acid diethyl esters. 3-Hydroxy-6-arylperhydropyrido[2,l-c][l,4]oxazin-4-ones first were reacted with triphenylphosphonium bromide in refluxing MeCN, then with 3-methoxy-4-(4-methyl-lH-imidazol-l-yl)benzaldehyde at ambient temperature in the presence of NEt3 to provide (Z)-3- l-[3-methoxy-4-(4-methyl-lH-imidazol-l-yl)phenyl]methylidene] derivatives (07USA2007/ 0117798, 08USA2008 /0207900). 

The a proton of a substituted cyclopropane is also rendered acidic if the substituent is attached to the ring by C-P bonds. A few reports have appeared on a-substitution in such compounds.(Cyclopropyl)triphenylphosphonium bromide was converted to a (1-ethoxy-carbonylcyclopropyl)triphenylphosphonium salt 18 in 80% yield by sequential treatment with lithium diisopropylamide and ethyl chloroformate. Furthermore, some diethyl cyclopropyl-phosphonates were converted, in some cases in excellent yield, to diethyl (1-hydroxymethyl-cyclopropyl)phosphonates by treatment with lithium diisopropylamide followed by addition of an aldehyde." Thus, typically, diethyl 2-hexylcyclopropylphosphonate gave diethyl 2-hexyl-l-[hydroxy(phenyl)methyl] cyclopropylphosphonate (19b) in 90% yield on reaction with benzaldehyde. ° Other electrophiles such as acetone, acetyl chloride, acetic anhydride, and ethyl acetate, were not sufficiently reactive to undergo addition to the anion. 

Diethyl 1-bromo-l.l-difluoromethylphosphonate has also been obtained in 92% yield by treating (bromodillnoromethyl)triphenylphosphonium bromide with excess triethyl phosphite in CI bC b at room temperatnre for 10 min. The proposed mechanism involves an insertion of difluorocarbene into bromotriethoxyphosphonium bromide. ""... 

Synthesis of five- and six-membered cycloalkenes has been achieved by the reaction of vinyl triphenylphosphonium bromide with ketomalonic esters of type (1), n = 1 to give 2[(2, n = 1) diethyl 3-methyl cyclopentenodicarboxylate]. 

An alternative route to the diethyl ester IV. 176 was also developed, involving a slow heterogeneous reaction (room temperature, 3 weeks) between 2,4-diamino-5-deazapteridine-6-carboxaIdehyde (IV. 181) and the ylide (IV. 182), generated from the corresponding triphenylphosphonium bromide salt with sodium hydride in V-methylpyrrolidone. The yield via this route was 35%. 

Hexadecanoic acid-CD-triphenylphosphonium bromide (5 mmol) was dissolved in tetrahydrofuran (THF) containing 10% HMPTA, and treated with two equivalents of potassium tert-butoxide at -10 C. One equivalent of TTF-carboxaldehyde, dissolved in THF, was added, and the mixture was stirred for 0.5 hour diethyl ether was added, and the product filtered off, and purified through acidic water-ether extraction, column chromatography (silica/ethyl acetate), followed by recrystallization from methanol, to provide ca. 500 mg of 3. 

Bis(trimethylsilyl)-1,4-xylene bis(triphenylphosphonium bromide) (3). A solution of 2,5-bis(trimethylsilyl)-l,4-bis(bromomethyl)benzene and tri-phenylphosphine in dimethyl formamide (DMF) is stirred and healed to reflux for 24 h. The resulting mixture is poured into diethyl ether. After filtration and vacuum drying, the monomer (3) is obtained as a white powder. 

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