Hydrophosphinylation alkynes

Another useful Rh-catalyzed reaction includes Ph2P(0)H addition to the triple bond of ethynyl steroids as air and water insensitive microwave-assisted hydrophosphinylation [91]. The reaction proceeded via the anti-Markovnikov addition, leading to the -/i-isomer. Rhodium complexes with hydrotris(3,5-dimethylpy-razolyl)borate ligand (Tp ) have shown catalytic activity in alkynes hydrophosphinylation with diphenylphosphine oxide [92]. Anti-Markovnikov products ( -)S-isomers) were formed in this reaction in moderate yields of 17-51%. Catalytic performance of Tp Rh(PPh3)2 and Tp Rh(cod) complexes was less efficient than [ClRh(PPh3)4] catalyst in the same conditions. 

Van Rooy S, Cao C, Patrick BO, Lam A, Love JA (2006) Alkyne hydrophosphinylation catalyzed by rhodium pyrazolylborate complexes. Inorg Chim Acta 359 2918—2923... 

Because organophosphorus compounds are important in the chemical industry and in biology, many methods have been developed for their synthesis [1]. This chapter reviews the formation of phosphorus-carbon (P-C) bonds by the metal-catalyzed addition of phosphorus-hydrogen (P-H) bonds to unsaturated substrates, such as alkenes, alkynes, aldehydes, and imines. Section 5.2 covers reactions of P(lll) substrates (hydrophosphination), and Section 5.3 describes P(V) chemistry (hydrophosphorylation, hydrophosphinylation, hydrophosphonylation). Scheme 5-1 shows some examples of these catalytic reactions. 

In closely related chemistry, Tanaka showed that Pd(PPh3)4 catalyzes addition of diphenylphosphine oxide to alkynes to give alkenyldiphenylphosphine oxides (hydrophosphinylation, Scheme 5-21). 

Scheme 5-22 Stoichiometric reactions relevant to the proposed mechanism for palladium-catalyzed hydrophosphinylation of alkynes...

Scheme5-24 Eq. (1) Proposed mechanism for Eq. (2) Stoichiometric reactions relevant to the phosphinic acid-modified palladium-catalyzed proposed mechanism hydrophosphinylation of alkynes.

Han, L.-B., Choi, N., and Tanaka, M., Oxidaative addition of HP(0)Ph2 to platinum(O) and palladium(O) complexes and palladium-catalyzed regio- and stereoselective hydrophosphinylation of alkynes, Organometallics, 15, 3259,... 

Han, L.-B., Hua, R., and Tanaka, M., Phosphinic acid induced reversal of regioselectivity in Pd-catalyzed hydrophosphinylation of alkynes with Ph2P(0)H, Angew. Chem., Int. Ed. Engl, 37, 94, 1998. 

Table 10 Rhodium-catalyzed hydrophosphinylation of alkynes with Ph2P(0)H...

The P—H bonds of primary phosphines RPH2 add to zirconocene to give unstable zirconium phosphido hydrides CpZr(H)(PHR) from which C—H activation products such as fulvalene complexes [CpZr(/A-PHR)]2(rf r -QoHg) can be isolated.44 The addition of Ph2P(0)H to M(PEt3)3 (M = Pd, Pt) gives (21-X) the Pd derivative catalyzes the hydrophosphinylation of alkynes.45... 

The oxidative addition of H-phosphonates (198) to platinum(O) complexes and the palladium-catalysed hydrophosphinylation of alkynes proceed stereo-spe-cifically with retention of configuration at phosphorus. The latter provides a convenient and general synthetic route to enantiomerically pure P-chiral al-kenylphosphinates (199) (an example is given in Scheme 50). ... 

General catalytic hydrophosphinylation reaction of alkenes and alkynes with hypophosphorous compounds (385) to give H-phosphinic acid derivatives (386) has been described. Compounds (386) are important biologically active compounds as well as being synthetic intermediates which can be converted into a variety of other organophosphorus compounds using well-established procedures. ... 

Harvey, R.G., Reactions of triethyl phosphite with activated olefins, Tetrahedron, 22, 2561, 1966. Pande, K.C., Hydrophosphinylation of activated alkenes or alkynes, Dow Chemical, U.S. Patent Appl. US 3622654, 1971 Chem. Abstr., 16, 46303, 1972. 

Neat reactions of liquid substrates can be quite successful. For example, the addition of P(0)-H bonds to alkenes has been accomplished using microwave irradiation in the absence of added solvent or catalyst (Scheme 25.4b). Tandem hydrophosphinylation reactions with alkynes afforded unsymmetrical species such as phosphine oxide—phosphinates. 

Scheme 5 Proposed mechanism for Rh-catalyzed hydrophosphinylation of an alkyne...

Similarly, Pd-catalyzed double hydrophosphinylation of 1-octyne was promoted by a novel metalloligand (Scheme 10) [19]. Oxidative addition of diphenylpho-sphine oxide to Pd(0) was proposed to yield a Pd hydride in which a phosphido-oxide (PR2(0)) ligand was stabilized by O-coordination to zirconium. After alkyne... 

Oxidative addition of Ph2P(0)H to M(PEt3)3 (M = Pd, Pt) takes place under ambient conditions (Eq. 3.44) [169]. In this reaction, the P-H bond initially oxidatively adds to the zero-valent group 10 metal complex to give a (hy-drido)metallacycle complex stabilized by an internal hydrogen bond. As shown in Scheme 3.85, the reaction is applied to catalytic hydrophosphinylation of terminal alkynes promoted by zero-valent palladium complexes. 

Han, Tanaka and co-workers described the hydrophosphinylation of alkynes by the optically pure phosphinate 38 in the presence of a Pd(II) complex as catalytic precursor (Scheme 6.16). 

DFT calculations shed light on the factors governing the selectivity of Pd-catalysed hydrophosphorylation, hydrophosphinylation, and hydrophosphination of alkynes with... 

Duraud A, Toffano M, Fiaud J-C. Regioselective metal-catalyzed hydrophosphinylation of alkynes synthesis of enantio-pure a- or (i-huhstituted vinylphosphane oxides. Eur. J. Org. Chem. 2009 2009 4400-4403. 

Han L-B, Zhao C-Q, Onozawa S-y, Goto M, Tanaka M. Retention of configuration on the oxidative addition of P—H bond to platinum(O) complexes the first straightforward synthesis of enantiomerically pure P-chiral alkenylphosphinates via palladium-catalyzed stereospecific hydrophosphinylation of alkynes. J. Am. Chem. Soc. 2002 124 3842-3843. 

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