Terminal vinylphosphonates

Catalyst 5-Hydroxypentylammonium acetate (5-HPAA reusable task-specific ionic liquid) Keywords Alkyl/aryl/heteroaryl aldehydes, nitromethane, trialkylphosphites, 5-HPAA, solvent-free, room temperature, one-pot tandem Henry-Michael reaction, multicomponent reaction, terminal vinylphosphonates... 

Sobhani, S., and Honarmand, M. (2013). A simple and efficient method for one-pot, three-component synthesis of terminal vinylphosphonates using a task-specific ionic hquid. Synlett, 24, 236-240. 

Synthesis of vinylphosphonate esters. Vinylphosphonates are a well-known class of organophosphorus compounds that are very useful intermediates for the construction of many synthetically and pharmaceutically important compounds including acyclic, carbocyclic, and especially heterocyclic compounds, p-aminophosphonates and l,2-epo)yallylphosphonates. ° Terminal vinylphosphonates (1-atyl or 1-allyl... 

Recently, Sobhani and Honarmand have developed a new and convenient room temperature protocol for the synthesis of a series of terminal vinylphosphonates (20) from the three-component reaction of aryl/alkyl/heteroaryl aldehydes (18), triall lphosphites and nitro-methane (19) in good yields through a one-pot tandem Henty-Michael reaction followed by nitro-elimination in the presence of 5-hydro-jypenlylammonium acetate (5-HPAA) as a reusable task-specific ionic liquid (Scheme 8). Use of a reusable and cost-effective ionic liquid as an environmentally benign reaction media, mild reaction conditions and operational simplicity are the key features of the present protocol. 

Scheme 8 Synthesis of terminal vinylphosphonates using a task-specific ionic-liquid,...

Substituted vinylphosphonates (195) and allylphosphonates (196) with E-olefin stereochemistry have been prepared for the first time via intermolecular olefin cross-metathesis (CM) using ruthenium alkylidene complex (197) in good yield. A variety of terminal olefins, styrenes and geminally substituted olefins has been successfully employed in these reactions (Scheme 49). ... 

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. ... 

Dialkyl vinylphosphonates, where the alkyl groups are methyl, ethyl, n-propyl, isopropyl, -butyl, and K-pentyl have been studied. The polymerization kinetics of these monomers indicate that chain termination may be by chain transfer through the alkyl groups of the monomer and that this chain transfer takes place in the later stages of polymerization [89]. 

Tanaka et al. were the pioneers of the synthetic application of catalytic hydrophosphorylations and hydrophosphinylations of multiple carbon-carbon bonds. Addition to alkynes was catalyzed by Pd complexes and led to vinyl-phosphonates in high yields under relatively mild conditions (Scheme 8.2) [66]. In some cases an excellent a-regioselectivity was reported. As an exception, trimethylsilylacetylene gave trans-jS-trimethylsilyl-vinylphosphonate in the addition reaction presumably due to steric hindrance. Various a-substituted vinylphospho-nates were synthesized from terminal alkynes in 80-95% yield and 92-96% regioselectivity using c -PdMe2(PPh2Me)2 as the catalyst precursor. 

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