Pyridine 1 -oxide—continued reactions with

Jacobsen (1999) has carried out carbomethoxylation of asymmetric epoxides. Thus, the carbomethoxylation of (R)-propylene oxide with CO and methanol yields 92% of (3R)-hydroxybutanoic acid in greater than 99% ee. Similarly, the reaction of (/ )-epichlorohydrin gives 96% of 4-chloro-(3R)-hydroxybutanoic acid in greater than 99% ee. The catalyst consists of dicobalt octacarbonyl and 3-hydroxy pyridine. A continuous process for making enantiomeric 1-chloro-2-propanol has been suggested. With a suitable catalyst propylene reacts with O2, water, cupric and lithium chloride to give 78% of (S)-l-chloro-2-propanol in 94% ee. 

Addition of a base (pyridine or methoxyethylamine), which can mix with the continuous phase to the cyclohexane-salt miniemulsion under stirring, provides reaction to oxides and hydroxides, e.g., from iron(III) chloride hexahydrate to iron(III) oxide. Here the crystal water steps into the reaction, while pyridine from the continuous phase neutralizes the eliminated HCl. Obviously, the interface area of the miniemulsion is high enough in order to allow this reaction. 

The spectroscopic probe pyridine-N-oxide was used to characterize polar microdomains in reverse micelles in supercritical ethane from 50 to 300 bar. For both anionic and nonionic surfactants, the polarities of these microdomains were adjusted continuously over a wide range using modest pressure changes. The solubilization of water in the micelles increases significantly with the addition of the cosolvent octane or the co-surfactant octanol. Quantitative solubilities are reported for the first time for hydrophiles in reverse micelles in supercritical fluids. The amino acid tryptophan has been solubilized in ethane at the 0.1 wt.% level with the use of an anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate (AOT). The existence of polar microdomains in aggregates in supercritical fluids at relatively low pressures, along with the adjustability of these domains with pressure, presents new possibilities for separation and reaction processes involving hydrophilic substances. 

The importance of fully or partially hydrogenated isoxazolo[2,3-a]pyridines as intermediates in the synthesis of stereochemically complex molecules, particularly alkaloids, has led to a continued high level of interest in their preparation. The route of choice remains the 1,3-dipolar cycloaddition reaction between a tetrahydropyridine A-oxide, that is a nitrone, and a dipolarophile. A number of methods for the production of the nitrone for in situ reaction have been developed. They include the oxidation of the secondary amine, piperidine, with hydrogen peroxide in the presence of... 

There has been continued interest in developing a process for direct esterification of terephthalic acid with ethylene glycol. It does not appear, however, that this is currently practiced on a commercial scale in the U.S. In Japan, a process was commercialized where terephthalic acid is reacted with two moles of ethylene oxide to form the dihydroxy ester in situ, as the starting material. One mole of ethylene glycol is then removed under vacuum in the subsequent condensation process. Also, it was reported that the polymer can be prepared by direct esterification at room temperature in the presence of picryl chloride. The reaction can also be performed at about 120 C in the presence of diphenyl chloro-phosphate or toluenesulfonyl chloride. This is done in solution, where pyridine is either the solvent or the cosolvent. Pyridine acts as a scavenger for HCl, that is a byproduct of the reaction, and perhaps also as an activator (by converting the acid into a reactive ester intermediate). 

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