Phosphinylation alkynes

Scheme 1 5-exo Cyclization initiated by phosphinyl radical addition onto an alkyne... 

The double phosphinylation of propargylic alcohols with diphenylphos-phine oxide to form 2,3-bis(diphenylphosphinyl)-1-propenes is catalyzed by a thiolate-bridged diruthenium complex (Scheme 28) [69]. It has been shown that the reaction proceeds via three ruthenium-catalyzed transformations propargylation of the phosphine oxide, alkyne to allene isomerization, and addition of phosphine oxide to the allene structure. 

Another interesting catalytic transformation involving alkynes is the hydro phosphinylation, which affords alkenylphosphine oxides [62]. The formation of hydride-phosphinito compounds is one of the key steps of the reaction. These species are formed by oxidative addition of the P-H bond of diphenylphosphine oxide to platinum(O) and palladium(O) complexes, which act as catalytic precursors. In this context, it should be mentioned that a novel method to prepare hydride-phosphinito compounds has been recently reported. The new strategy starts from 133 and involves the oxidative addition of the P-H bond of... 

The addition of phosphorus pentachloride to alkenes and alkynes yields complexes of the type RPClj PClg, which, when treated with sulphur dioxide, will give phosphonyl chlorides (6.197). Hydrolysis of the aluminium trichloride complexes (6.151) and (6.152) will also give phosphonyl or phosphinyl halides (6.198). 

An alternative method for the synthesis of tran -alkenyl /f-phosphinates involved AIBN initiated radical addition of ethyl phosphinate to alkenes and alkynes. The method was applied to the preparation of GABA analogues. A new route to chiral phospholanes has been presented. Enantiomerically pure P-chiral dicyclohexyl-ammonium 2-(phosphinyl)acrylates (236) have been obtained by an asymmetric Michael reaction with imine, which opens a new general route to the enantioselective synthesis of a-methylene-6-valerolactones (237) (Scheme 97). ... 

The synthesis of chiral vinylphosphines based upon the palladium-catalyzed hydro-phosphinylation of alkynes has been described (Scheme 4.305) [471]. As with many asymmetric palladium-catalyzed reactions, the key to this chemistry was the use of a chiral... 

Komeyama and Takaki have described the hydrophosphination of enynes with diphenylphosphine to generate 1-phosphinyl-1,3-dienes as the sole products in excellent yields after oxidative workup. In the reported case, conjugated enynes are generated in situ by selective dimerization of terminal alkynes [187]. The same authors later developed the ytterbium catalyzed dual hydrophosphination of conjugated diynes with 2 equiv. of diphenylphosphine. The corresponding 1,4-bis (diphosphinyl)buta-1,3-dienes are then efficiently isolated after oxidative work-up. Formation of (Z,Z) diastereomers is favored with disubstituted diynes, while ( ,Z) diastereomers are mainly obtained from terminal diynes (Scheme 94) [188]. 

Scheme 8.34 Proposed mechanism of Pd-catalyzed dehydrogenative double phosphinylation of terminal alkynes with diphenylphosphine oxide...

Dobashi N, Luse K, Hoshino T, Kanada J, Kashiwabara T, Kobata C, Nune SK, Tanaka M (2007) Palladium-complex-catalyzed regioselective Markovnikov addition reaction and dehydrogenative double phosphinylation to terminal alkynes with diphenylphosphine oxide. 

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