Acetates addition

In the first publication describing the preparative use of an enzymatic reaction in ionic liquids, Erbeldinger et al. reported the use of the protease thermolysin for the synthesis of the dipeptide Z-aspartame (Entry 6) [34]. The reaction rates were comparable to those found in conventional organic solvents such as ethyl acetate. Additionally, the enzyme stability was increased in the ionic liquid. The ionic liquid was recycled several times after the removal of non-converted substrates by extraction with water and product precipitation. Recycling of the enzyme has not been reported. It should be noted, however, that according to the log P concept described in the previous section, ethyl acetate - with a value of 0.68 - may interfere with the pro-... 

Hiller and Funke obtained easily dissolvable linear macromolecules of PVS by anionic polymerization of 1,4-DVB up to conversions of 80-90% [230,231]. In these experiments very low concentrations of n-butyl lithium (n-BuLi) were used and tetrahydrofuran (THF) as solvent. The reactions were carried out at -78 °C and for 7 min. The contents of pendant vinyl groups in the polymer were determined by infrared spectroscopy, mercury-II-acetate addition and catalytic... 

Silyl ketene acetal addition to nitrone (292) is likely to generate four diastere-omers. Depending on the employed Lewis acid, either O-silylhydroxylamines or free hydroxylamines (Scheme 2.175) are obtained (635). 

The reaction of silyl ketene acetal addition to nitrones has been used for the synthesis of optically active (2S,3S)-benzoyl- and /V- oc-phenyl isoserine (636a) of isoxazolidine nucleoside-analog of thymine polyoxine C(636b) and of... 

The route for the cyclization was easier to determine than the identification of the very reactive isoprene unit, and was understood in outline by 1960. Studies of labeled compounds detected within 10 min. of 14C-acetate addition to intestinal preparations showed label in squalene, lanosterol, and a further, unidentified ring compound, all with higher specific activities than cholesterol. By 75 min cholesterol was the main labeled compound. Clayton and Bloch then confirmed that lanosterol, previously known from sheep s wool, was converted to cholesterol with the extra three (methyl) carbon atoms being lost as carbon dioxide. 

Among some metal oxygen compounds which add, palladium and thallium ion both oxidize olefins and apparently the initial step is the addition of a metal hydroxide across the olefin double bond. The intermediates have not been isolated because they go on to other products but kinetic and other evidence indicates that the addition of the hydroxide is the initial step. In the well known mercury acetate addition to olefins in alcohol solution one can isolate the /S-hydroxv or alkoxy ethylmercury derivatives. 

Extraction of milk 3 times with 70% acetonitrile in water, filtration, removal of fat by zinc acetate addition, and partitioning with methylene chloride. Reduction of volume after drying. 

Two patents by Takahashi et al. reported the synthesis of vitamin A via a Cio dihalogeno derivative [34,35]. In one procedure the halogenodiene was prepared by bromination of 3,7-dimethyl-2,5,7-octatrien-1-yl acetate. Addition of the latter and /BuOK in DMF to the Cio sulfone provided the retinol sulfone (34%). Again, double elimination (MeOK), gave vitamin A acetate, Fig. (13). 

Formaldehyde anion synthon ( CHO). The anion of 1 (n-BuLi, THF, 0°) is readily alkylated, particularly by primary halides. The products can he converted into aldehydes under very mild conditions. Oxidation with m-chloroperbenzoic acid gives an unstable sulfoxide, which undergoes an sila-Pummerer rearrangement to an acetal. Addition of water liberates the free aldehyde. Epoxides can also be used as electrophiles.2 3 Example ... 

The foregoing nitric acid solution of polymerised c /cZoselenopropane after removal of the oxalic acid gives a viscous residue. After treatment with sodium acetate, addition of potassium iodide precipitates the brick-red diselenodi-iodide. The di-iodide occurs when hydriodic acid acts on trimethylenediselenious acid or when a chloroform solution of C2/cZotrimethylene diselenide is treated with iodine. It dissolves in warm chloroform or benzene, but is very sparingly soluble in acetone or alcohol it melts to a red liquid at 124° C. 

In contrast to titanium(IV) tetrachloride, which causes polymerization of a,3-unsaturated esters, aluminum triflate88 or aluminum-impregnated montmorillonite87b are excellent promoters of silyl ketene acetal additions to a,(3-unsaturated esters (Scheme 35). Similarly, the addition of silyl ketene acetals and enol silyl ethers to nitroalkenes, followed by Nef-type work-up, affords y-keto esters (216) and y-di-ketones (218), respectively (Scheme 35).89a>89b Mechanistically, the y-diketones (218) arise from Nef-type hydrolysis of an initial nitronate ester (217).89e 89d Mukaiyama reports that SbCls-Sn(OTf)2 catalyzes diastereoselective anti additions of silyl ketene acetals, silyl thioketene acetals and enol silyl ethers to a,(3-unsaturated thioesters (219).90... 

Catalysis with Bisoxazoline Complexes of Sn(II) and Cu(II). The bisoxazoline Cu(IT) and Sn(II) complexes 81-85 that have proven successful in the acetate additions with aldehydes 86,87, 88 also function as catalysts for the corresponding asymmetric propionate Mukaiyama aldol addition reactions (Scheme 8B2.8) [27]. It is worth noting that eithersyn or anti simple diastereoselectivity may be obtained by appropriate selection of either Sn(II) or Cu(II) complexes (Table 8B2.12). 

IV. Palladium Acetate Addition with Hydride Elimination... 

The palladium acetate addition to 1-olefins in acetic acid solution is predominately of the Markovnikov type producing ketone enol esters 14>. 

These reactions were also carried out in an aqueous/ethanolic medium with sodium acetate addition to control the pH2. Examples of 3,5-dioxotellurane dioximes prepared in this manner are ... 

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