Phosphine oxide synthesis

Okamoto, Y, and Azuhata, T., Synthesis of dialkyl 3-(dialkylphosphinyloxy)-2-alkenephosphonate and diphenyl-[3-(diphenylphosphinyloxy)-2-propenyl]phosphine oxide. Synthesis, 941, 1986. 

The red metastable product obtained from potassium hydroxide and phosphorus does not appear to be an intermediate in this tertiary phosphine oxide synthesis. A solution of the red compound prepared separately in etlianol was not decolorized by acrylamide, and only minor amounts of the tertiary phosphine oxide were obtained. This result... 

Tazelaar CGJ, Lyaskovskyy V, van Dijk T, et al. Tris(pyrazolyl)phosphine oxides. Synthesis and coordination chemistry with copper(l). Organometallks. 2012 31 3308-3315. 

Much effort has been placed in the synthesis of compounds possessing a chiral center at the phosphoms atom, particularly three- and four-coordinate compounds such as tertiary phosphines, phosphine oxides, phosphonates, phosphinates, and phosphate esters (11). Some enantiomers are known to exhibit a variety of biological activities and are therefore of interest Oas agricultural chemicals, pharmaceuticals (qv), etc. Homochiral bisphosphines are commonly used in catalytic asymmetric syntheses providing good enantioselectivities (see also Nucleic acids). Excellent reviews of low coordinate (coordination numbers 1 and 2) phosphoms compounds are available (12). 

A lV -Bis p-carbomethoxy benzoyl) butanediamine (T4T-dimethyl), synthesis of, 107-108 Bischloroformates, reaction with dicarboxylic acids, 87 Bis(4-chlorophenyl)phenyl phosphine oxide (BCPPO), 345... 

Poly(arylene ether ketone)s (PEKs), 327 block and graft copolymers of, 359-361 hyperbranched, 349 modification of, 354 synthesis of, 340-345, 360 Poly(arylene ether phosphine oxide)s (PEPOs), 345... 

As mentioned in Sect. 2.2, phosphine oxides are air-stable compounds, making their use in the field of asymmetric catalysis convenient. Moreover, they present electronic properties very different from the corresponding free phosphines and thus may be employed in different types of enantioselective reactions, m-Chloroperbenzoic acid (m-CPBA) has been showed to be a powerful reagent for the stereospecific oxidation of enantiomerically pure P-chirogenic phos-phine-boranes [98], affording R,R)-97 from Ad-BisP 6 (Scheme 18) [99]. The synthesis of R,R)-98 and (S,S)-99, which possess a f-Bu substituent, differs from the precedent in that deboranation precedes oxidation with hydrogen peroxide to yield the corresponding enantiomerically pure diphosphine oxides (Scheme 18) [99]. 

Scheme 18. Example of synthesis of enantiomerically pure phosphine oxides...

The combined use of the oxidation of a free phosphine [99] and stereospecific reduction of the phosphine oxide [74] was employed for the synthesis of (R,R)-f-Bu-BisP from (S,S)-BisP itseLf. Specifically, (S,S)-BisP was deboronated (TfOH/KOH), oxidized (HjOj), and reduced (MeOTf/LiAlH4) [74], producing, unfortunately, low yields of the desired counter-enantiomer. 

Although of limited success, this Ni-catalysed coupling strategy builds on a previous report of the successful, direct synthesis of poly(4,4 -diphenylphenyl-phosphine oxide) (70c) from bis(p-chlorophenyl)-phenylphosphine oxide (71) (Scheme 21) [66]. The white soluble material (70c) (Aj ax 280 nm) was found to have a single phosphorus environment by NMR spectroscopy, a comparatively high molecular weight (Mn= 15,300) together with a low molecular... 

B. By Hydrolysis Reactions.—Details have appeared of the synthesis of dibenzophosphorin oxides (15) from 5-alkyldibenzophospholes, by reaction with methyl propiolate in the presence of water, and of confirmatory syntheses from phosphinic acid chlorides, as shown below. Evidence for the suggested mechanism of the ring-expansion reaction is presented. The hydrolysis of enamine phosphine oxides is an efficient, although somewhat indirect, method for the preparation of j8-ketoalkylphosphine oxides (16) [see Section 3(iii), for the preparation of enamine oxides]. Reasonable yields (48—66%) of trialkylphosphine oxides (17) have been obtained by the alkaline hydrolysis of the products from the pyrolysis at 220 °C of red phosphorus with alkyl halides, in the presence of iodine. 

D. Miscellaneous.—A further study of the reactions of diphenyl-phosphine oxide with tetracyclone has confirmed that the reaction yields the oxide (30) under mild, basic conditions, and that the reaction is thermally reversible. The displacement of halogen from phosphorus by amino-compounds has been used in the synthesis of a number of aminofluoro-phosphine oxides (31), and of A-methyl-AA-bis(dichlorophosphinyl)-amine (32). ... 

A polymer containing side-chain benzylphosphonium residues has been prepared and used in olefin synthesis. A suspension in THF was treated with base and benzaldehyde overnight and the polymeric phosphine oxide was then removed by filtration. The yields of stilbenes, 40% with potassium t-butoxide and 60% with sodium hydride, were not improved by using an excess of base or of aldehyde. 

Full details have appeared of the generation and use in synthesis of the chlorofluoromethylene-ylide (103). Fluoromethylenetriphenylphosphorane (104) has been prepared as shown and among other unusual ylides used in normal olelin synthesis are (105), (106), (107), (108), and (109). The latter gave acyclic phosphine oxides (110) in up to 50% yield. 

Phosphine oxide-based olefin synthesis is being increasingly used and is the method of choice in a number of recent syntheses of natural products and related compounds. 

Phosphine oxide-based olefination has been increasingly used as a synthetic method. The phosphine oxide (62). required for a synthesis of 3-milbemycin (64). has been prepared as a mixture of... 

Reflecting similar developments throughout organic chemistry there has been a notable increase this year in the number of theoretical studies of ylides and their reactions. Methods of olefin synthesis involving phosphine oxides are discussed in Chapter 3. 

A modification of this procedure allowed the isolation of 1,3,2-oxazaphospholidine 52a as a single diastereomer [41] and its application to asymmetric synthesis of enantiomerically and diastereomerically pure phosphinic acid derivatives 53 and 54 and tertiary phosphine oxides 55 (Scheme 20) [45], A few years later, a similar approach for the synthesis of enantiomerically pure tertiary phosphine oxides 55... 

Scheme 45 Synthesis of diastereomerically pure o-hydroxyaryl phosphine oxides 162a and 162b...

An analog (56) of isomer 53 was prepared by a structure proving synthesis (Scheme 13). It was proved that the syn isomer (57) obtained after deoxygenation is transformed spontaneously to the anti form (58). Phosphine (58) was stabilized as the phosphine oxide (59) (Scheme 14) [55],... 

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