690-64-2Relevant academic research and scientific papers
Organophosphorus chemistry. Part 1: The synthesis of alkyl methylphosphonic acids
Timperley, Christopher M.,Bird, Michael,Holden, Ian,Black, Robin M.
, p. 26 - 30 (2007/10/03)
Several alkyl hydrogen methylphosphonates of structure RO(HO)P(O)Me were synthesised by a three-stage route [R =i-Pr, n-Bu, i-Bu, s-Bu, pinacolyl Me3C-CH(Me)-, cyclopentyl and cyclohexyl]. Trimethyl phosphite was transesterified with alcohols in the presence of sodium catalyst to give the mixed phosphites (MeO)2POR in 6-64% yield. Treatment of these with methyl iodide gave alkyl methyl methylphosphonates RO(MeO)P(O)Me in 66-95% yield. Selective demethylation of these compounds by bromotrimethylsilane, followed by methanolysis of the phosphorus silyl esters RO(Me3SiO)P(O)Me, gave the hydrogen phosphonates in 60-97% yield.
Structure and reactivity of mixed alkali metal alkoxide/aryloxide catalysts
Kissling,Gagne
, p. 9005 - 9010 (2007/10/03)
The average solution aggregation state of the ester interchange catalyst 1, obtained by mixing 1 equiv of NaOt-Bu and 3 equiv of NaOC6H4-4-t-Bu, was determined to be 4.0 by vapor pressure osmometry (VPO) in THF. Low-temperature 1H NMR spectra of 1 indicated that the THF solution contained a mixture of tetrameric clusters. On the basis of symmetry arguments and the sensitivity of the different species to the alkoxide/aryloxide ratio, the compounds were determined to be mixed clusters with 0:4, 1:3, 2:2, and 3:1 mixtures of the NaOt-Bu and NaOC6H4-4-t-Bu components. On a per -Ot-Bu basis, each cluster has a similar absolute activity, though the aryloxide-rich catalysts are significantly longer-lived. Unlike 1, catalysts containing ortho-substituted aryloxides, 2, do not give a strictly statistical distribution of clusters, and the activities of these catalysts depend on steric and electronic factors, though the absolute rate differences are not large.
Alkali metal alkoxide clusters: Convenient catalysts for the synthesis of methylphosphonates
Kissling, Rebecca M.,Gagne, Michel R.
, p. 1585 - 1590 (2007/10/03)
Alkali metal alkoxides are good catalysts (1-8 mol %) for promoting the interchange reaction between carbonyl and phosphorus esters. This reactivity leads to convenient methodologies for the synthesis of symmetric and unsymmetric alkyl-substituted methylphosphonates from dimethyl methylphosphonate (DMMP). Reactions rates are high with initial turnover frequencies (N(t)) in excess of 1 x 106 h-1 observed and with KO(t)Bu > NaO(t)Bu > LiO(t)Bu. The reactions were sensitive to steric effects in the product methylphosphonates with reaction rates paralleling the size of the transferring alkoxide (n-alkyl > isoalkyl >> tert-alkyl). For the test reaction DMMP + isopropyl acetate, substitution kinetics were consistent with a scenario wherein each methoxide is replaced sequentially, and the substitution rate for the second displacement is substantially slower than the first. Kinetic studies on the first substitution process were indicative of a concentration dependent rate law; a scenario most easily accounted for by a coupled transesterification wherein alkoxide reversibly and independently adds to phosphonate and ester.
REACTION OF PROPOSED PHOSPHOROTHIOLATE S-OXIDE INTERMEDIATES WITH ALCOHOLS
Segall, Yoffi,Casida, John E.
, p. 209 - 212 (2007/10/02)
S-Oxide 2 is an extremely reactive intermediate.Its phosphorylation vs rearrangement rates, strongly depend upon the nature of the nucleophile.
