Phenylphosphine oxides, reactions

Preparation of bis(4-methoxyphenyl)phenylphosphine oxide — Reaction of a Grignard reagent with a phosphorus halide... 

A further illustration has appeared28 of the reactivity of simple a-keto-alkyldi-phenylphosphine oxides (31) towards addition reactions, as outlined in Scheme 5. In the same paper, alkylation of chloro(di-t-butyl)phosphine (32) by alkyl benzoates is described 28 see Chapter 3 for details. A similar acylation reaction of tetramethyl-diphosphine disulphide (33) has been described, although the acetylphosphine sulphide (34) was not isolated.29... 

Under the reaction conditions it spontaneously fragments to give the product alkene and tri-phenylphosphine oxide. 

In 1962, Mannerskantz and Wilkinson described the reactions of [Mo(CO)4(2,5-dithiahexane)l with X2 (X = Br, I) to give the seven-coordinate complexes [MoX2(CO)3(2,5-dithiahexane)]. Treatment of the oxygen donor ligand complexes [M(CO)3(RPPh)] (M = Mo, W) RPPh = bis[(di-phenylphosphinyl)methyl]phenylphosphine oxide, [M2(CO)6(MDPO)] MDPO = methylenebis[diphenylphosphine oxide], and [M(CO)4(R... 

Complex 6 also exhibits catalytic activity in the oxidation reaction of various other substrates such as PPh3, dibenzylamine, and CO, with formation of tri-phenylphosphine oxide, /V-benzylidenebemzylamine, and C02, respectively. 

Reaction of the organophosphide from phosphorus and phenyllithium with propylene oxide, followed by hydrolysis, gave bis(2-hydroxypropyl)-diphenylphosphonium bromide in 19% yield and 2-hydroxypropyldi-phenylphosphine (6). The latter was obtained as the methiodide in 19% yield. Reaction of the complex lithium phenylphosphide with benzaldehyde gave bis(a-hydroxybenzyl)phenylphosphine oxide in 12% yield (6). 

Morgan and Herr noted previously that di-(p-tolyl) methylphosphine oxide formed in 60% of the theoretical amount from diphenyl methyl-phosphonate with a one mole excess of p-tolyl Grignard reactant (148). No effort was made to imcover optimum conditions. Similarly, diallyh phenylphosphine oxide and other monomers were made by this general route (12,13). An excellent method for the synthesis of diphenyl alkyl-phosphonates was developed recently (126). No report has revealed an attempt to effect single displacement on phosphonates to give phos-phinates, and the effort to do so would probably be unprofitable. Phos-phinates have not been investigated in this type of reaction, but rapid conversion to phosphine oxides would be expected in spite of the mild... 

In terms of its chemical reactivity, an ylid such as 126 may be viewed as a phosphorus-stabilized carbanion that will undergo acyl addition with an aldehyde or a ketone. When this ylid is mixed with cyclohexanone (80), there are two isolated products. The one that is more interesting to an organic chemist is methylenecyclohexane (129), formed in 52% yield the other is tri-phenylphosphine oxide, 130. It is obvious that 129 is not the expected acyl addition product. Formation of 130 indicates that the carbon atom of the ylid has been transferred to the ketone, but the oxygen atom of the ketone has been transferred to the phosphorous atom. Analysis of the reaction shows that the oxygen atom is lost from the ketone, and the CH2 unit of ylid 126 is transferred to form a new C=C bond (in green in the illustration). What is the mechanism ... 

The use of the phosphonate ester (Homer-Wadsworth-Emmons reaction) allows much easier separation of the product alkene, since the sodium phosphate byproduct is water soluble the byproduct of fhe Wiffig reaction, tri-phenylphosphine oxide, is not water soluble. In the Horner-Wadsworth-Emmons modification, a conjugated, or electron-withdrawing, substituent (such as a phenyl or carbonyl group) on the nucleophilic carbon is used to assist in the stabilization of the carbanion. This modification (Experiment [19B]) maybe used as an alternative to Experiment [19A] for the preparation of (E)-stilbene. The "instant-ylide" Wittig reaction yields predominantly the E isomer of... 

General procedure. N-Vinylcarbodiimides 1732 [1268] To a solution of iminophos-phorane 1731 (5.27 mmol) in dry benzene (50 mL) was added dropwise a solution of the isocyanate 1730 (5.83 mmol) in benzene (50 mL). The reaction mixture was stirred at room temperature for 1-2 h (R = aryl, -styryl) or for 1-2 d (R = alkyl). Evaporation of the solvent and trituration of the residue with hexane afforded tri-phenylphosphine oxide as colorless crystals, which were filtered off. Removal of the solvent from the filtrate and short column chromatography of the residue (silica gel benzene/hexane, 1 5) gave the carbodiimides 1732 as viscous oils or solids in yields of around 70%, which were immediately used in the next reaction. Attempts to purify them by distillation under reduced pressure failed. 

Scheme 10.55. A representation of the Wittig reaction utUizing chiral benzylethylmethyl-phenylphosphoninm iodide and phenyllithium to generate the ylid and reaction of that intermediate with benzenecarboxyaldehyde (benzaldehyde) to produce chiral ethylmethyl-phenylphosphine oxide and ( )-stilbene. As shown, the number of possible intermediates is limited by the requirements of retention of chirality and production of a single stilbene (Wittig, G. Rieber, M. Liebigs Ann. Ghent., 1949,562,187).

The next examples for the preparation of phosphine chalcogenides are based on the reactions of phosphines with oxygen, sulfur and selenium. Ortho- and tneta-pyrazolylphenyl phenylphosphine oxides were obtained by making available the corresponding triarylphosphines and treating them by hydrogen peroxide (Scheme 3). ... 

Scheme 5.1 Reaction sequences employed for the prep- bis(4-fluorophenyl)phenylphosphine oxide producmg aration of 2,5-bis(4-hydroxyphenyl)pyridine and 2,6-bis Homopolymers I and II, respectively. Reproduced fiom (4-hydroxyphenyl)pyridine and their polymerization with [7] with permission of the American Chemical Sodely...

The reaction of phenylphosphine oxides (197) with internal alkynes, mediated by AcOAg, has been found to proceed as a dehydrogenative annulation, involving C-H... 

Biphilic Reactions with Dienes or Carbonyl Compounds. Stereochemical details have appeared of the reactions between substituted 1,3-dienes and halogenophosphines, such as dichloromethylphosphine (21a) and dibromo-phenylphosphine (21b). In general, both cis- and /ra/i5-adducts are formed, and they are not interconvertible via quinquecovalent intermediates. The conversion of these adducts to A -phospholens or to A -phospholen-l-oxides produces cis-trans mixtures. 

Addition of diphenylphosphine or phenylphosphine to methyl 1-cyclohexanecarboxylate under base catalysis yielded 186 and 187 [164] (Figure 17). The Pd-catalyzed Heck reaction of substituted olefins with (p-bromophenyl)diphenylphosphine oxide in dimethylformamide afforded substituted phosphine oxides which could be reduced with trichlorosilane to yiled the corresponding carboxylatedphosphines - 188, too, was prepared this way [165],... 

---