Ethyldiphenylphosphine

Deamination reactions of (2-amino-l,l-dimethyl)ethyldiphenylphosphine oxide (57) result in the formation of three products, in each of which the diphenylphosphinyl group has migrated to the primary carbon of the starting material. These reactions are unusual examples of non-assisted migration of a phosphinyl group. 

Recently, the same procedure has been used by Williams and coworkers in their approach to the natural product (-)-stemonine (7-18) [10], an alkaloid which exhibits broad biological activity [11]. Conversion of the formyl azide 7-16 in a Staudinger reaction with ethyldiphenylphosphine first generated a phosphineimide which was used for the subsequent aza-Wittig process (Scheme 7.7). The furnished seven-... 

Yamashita, M., Tsunekawa, K., Sugiura, M., and Oshikawa, T., Novel preparation of diphenylphosphine oxides via direct deoxygenation of 1,2-epoxy-ethyldiphenylphosphine oxides, Synthesis, 65, 1985. 

Preparation of alkyldiphenylphosphine oxides. General procedure from phospho-nium salts. Triphenyl phosphine is heated under reflux with an excess of alkyl halide. The precipitated phosphonium salt is filtered off, washed well with ether, and then heated with 30 per cent w/w aqueous sodium hydroxide (c. 4 ml/g) until all the benzene has distilled out. The mixture is cooled and extracted with dichloromethane, and the extracts are dried (magnesium sulphate) and evaporated to dryness. In this way ethyldiphenylphosphine oxide is obtained from triphenyl phosphine (65.6 g, 0.25 mol) and iodoethane (42.9 g, 0.275 mol) in dry toluene (250 ml) to give first the phosphonium salt (102.4 g, 97.9%) after 3.5 hours, from which the phosphine oxide is obtained as needles (53.2 g, 92.5%), m.p. 123-124 °C (from ethyl acetate) p.m.r. 5 (CDC13, TMS) 1.9-13 (m, 10H, Ph2PO), 2.3 (m, 2H, CH2) and 1.2 (dt, 3H, JHm, = 7 Hz, JMeP = 17 Hz, Me). 

An unstable tri(perfluorophenyl)phosphine complex can be obtained by oxidative addition of chlorine to the dimeric rhodium(I) complex. The ethyldiphenylphosphine complex prepared in this way is more stable (equation 202). 

The present procedure starts with ethyldiphenylphosphine, which is cleaved by lithium in tetrahydrofuran to lithium ethylphenylphosphide. This phosphide under vigorous reflux cleaves tetrahydrofuran to afford a necessary precursor, 4-(ethylphenylphosphino)-1 -b utanol (ethyl(4-hydroxybutyl)pheny Iphosphine). This(hydroxyalkyl)phosphine then is cyclized intramolecularly to give 1-ethyl-l-phenylphospholanium perchlorate. 

The preparation of ethyldiphenylphosphine has been reported and the compound is available commercially. The total working time for preparations A and B is approximately days. Utilization of this procedure has been found to be of general applicability to other phospholanium salts. ... 

Caution. In common with other alkyldiarylphosphines, ethyldiphenylphosphine presents some hazard because of its toxicity and susceptibility to air oxidation. Therefore, all operations must be performed in an efficient hood with manipulations conducted under an inert atmosphere. All ground-glass joints should be greased thoroughly with a silicone lubricant. 

A 500-mL, three-necked flask is equipped with a mechanical stirrer, a pressureequalizing dropping funnel, and a reflux condenser, the entire system having been previously flushed with nitrogen. To the flask is added (under nitrogen) 1.4 g (0.2 mole) of lithium shavings, 21.4 g (0.10 mole) of ethyldiphenylphosphine, and 200 mL of anhydrous tetrahydrofuran. After it is stirred for 1... 

At a mercury cathode the propensity for cleavage from a phosphonium salt in methanol increases in the sequence methyl < ethyl < -butyl phenyl < tert-huiy < allyl < benzyl however, at a lead cathode the tendency for loss of an alkyl group from an alkyltriphenylphosphonium group is much higher than at a mercury cathode ethyltriphe-nylphosphonium chloride is thus reduced in methanol at a mercury cathode to a 5 3 mixture of ethyldiphenylphosphine and triphenylphosphine, whereas 91% triphenylphos-phine was isolated at a lead cathode [196]. 

R)-1 - (.S )-2-Formylfcrroccnyl ethyldiphenylphosphine (0.270 g, 0.613 mmol), and ethylamine (5 mL) were placed in a 25-mL round-bottomed flask under nitrogen. The mixture was stirred at 40 °C for 6 hours. The excess of the amine was then evaporated under a stream of nitrogen to give a brown-orange compound. 

Ethyldiphenylphosphine oxide 397 Diphenylphosphinic acid (0.22 g) is converted into the acid chloride by 1-2 hours boiling under reflux with thionyl chloride (0.5 ml) in toluene. About half the solvent is then distilled off and the residual solution is diluted with benzene and dropped at room temperature into a Grignard solution prepared from magnesium (0.25 g) and ethyl bromide (2.5 ml). The reaction is complete after half an hour s boiling under reflux. The product is hydrolysed by ice and hydrochloric acid, the aqueous layer is washed with ether, and ether phases are united, dried, and evaporated. The residue is subjected to steam-distillation and then extracted several times with ether. The residue left on evaporation of these extracts crystallizes at once or on short storage and is decolorized in acetone by charcoal. Recrystallization from ether-light petroleum or aqueous acetone affords the oxide, m.p. 123-124° (67%). 

An X-Tay structirre determination has been reported for the 1,2-oxaphosphetan (18), obtained from ethyldiphenylphosphine and hexafluoroacetone. Oxaphosphetans are probably formed from hexa-fluoroacetone and phosphines containing an a-hydrogen via the ylides (20), formed by proton transfer in the initial 1 1 adducts (19). 

Ethyldiphenylphosphine, 2115(06115)2 , is obtained as a colourless, strongly refractive oil, B.pt, 203° ., having a pungent odour, and readily undergoing oxidation with formation of ethyldiphenylphosphine oxide. 

Diethyldiphenylphosphonium iodide, (C2H5)2(C6H5)2PI, obtained from ethyldiphenylphosphine and ethyl iodide, forms colourless... 

Ethyldiphenylphosphine oxide, (C2Hg)(C6H5)2TO, occurs when the phosphonium compound is treated with silver oxide as before, or can be obtained from ethyl diphenylphosphinite, (CgH5)2P.OC2H5, under the catalytic influence of ethyl iodide at room temperature. It separates from boihng ether in colourless, glistening prisms, M.pt. 121° C. 

Ethyldiphenylphosphine sulphide, (C2H5)(CgH5)2PS, occurs when ethyl diphenylthiophosphinite, (CgH5)2P.SC2H5, is heated with ethyl iodide in a sealed tube at 100° C. It crystallises in rhombic tablets, M.pt. 65-5° to 66° C. 

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