Hydrophosphonylation alkynes

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. 

Scheme 5-18 Stoichiometric reactions relevant to the proposed mechanism for palladium-catalyzed hydrophosphonylation of alkynes...

The hydrophosphonylation (addition of dialkyl phosphonates), hydrophos-phinylation (addition of alkyl alkylphosphinates or alkyl phosphinates) and addition of secondary phosphine oxides to unfunctionalized alkenes and alkynes occur under free radical conditions or with transition metal catalysis.10,39 63 90... 

The Pd-catalyzed hydrophosphonylation of terminal alkynes with dialkyl phospliites seems destined to become the method of choice for tlie synthesis of a-substituted vinylphosphonates. The reaction proceeds by regioselective attack of dialkyl phosphite at the internal carbon of the triple bond (Scheme 6.37). Thus, 5-cyano-l-pentyne reacts efficiently with dimethyl phosphite in the presence of cZv-PdMe2(PPh2Me)2 affording dimethyl l-(3-cyanopropyl)vinylphosphonate in 94% yield. In the absence of catalyst, the hydrophosphonylation product is not detected. ... 

Scheme 7 Pd-catalyzed alkyne hydrophosphonylation with a trifluoroacetic acid additive...

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