Tetrahydrofuran , as solvent

Syt thf ttha sjmaptotagmin tetrahydrofuran (as solvent, ligand) triethylenetetramine-AT, N, N, N, N", AT"-hexaacetate... 

The substrate-controlled diastereoselective addition of lithiated alkoxyallenes to chiral nitrones such as 123, 125 and 126 (Scheme 8.32) furnish allenylhydroxyl-amines as unstable products, which immediately cydize to give enantiopure mono-orbicyclic 1,2-oxazines (Eqs 8.25 and 8.26) [72, 76]. Starting with (R)-glyceraldehyde-derived nitrone 123, cydization products 124 were formed with excellent syn selectivity in tetrahydrofuran as solvent, whereas precomplexation of nitrone 123 with... 

With conventional techniques and electrolytes, it was not possible to obtain living anions because they are rapidly protonated by tetraalkylammonium salts and residual water. The first report of the production of living polymers by an electrolytic method has to be attributed to Yamazald et al. [247], who used tetrahydrofuran as solvent, and LiAlH4 or NaAl(C2H5)4 as electrolyte for the polymerization of a-methylstyrene. A similar technique was used to polymerize styrene as well as derivatives [248-252]. 

GPC is a promising method for examination of template polymerization, especially copolymerization. Copolymerization of methacrylic acid with methyl methacrylate in the presence of polyCdimethylaminoethyl methacrylate) can be selected as an example of GPC application for examination of template processes. The process was carried out in tetrahydrofurane as solvent at 65°C. After proper time of polymerization, the samples were cooled, diluted by THF, filtered, and injected to GPC columns. Two detectors on line UV and differential refractometer, DRI, were applied. UV detector was used to measure concentration of two monomers, while the template was recorded by DRI detector (Figure 11.3) The decrease in concentration ofboth monomers can be measured separately. It was found that a big difference in the rate of polymerization between template process and blank polymerization exists. The rate measured separately for methacrylic acid (decrease of concentration of methacrylic acid in monomers mixture) was much higher in the template process. Furthermore, the ratio ofboth monomers changes in a different manner. Reactivity ratios for both monomers can be computed. Decrease in concentration during the process is shown in Figure 11.4. 

The hydroboration amination sequence in diglyme is a general procedure for the conversion of olefins to primary amines without rearrangement and with predictable stereochemistry.5 An alternative procedure, using tetrahydrofuran as solvent and either hydroxylamine-O-sulfonic acid or chloramine, is applicable with terminal olefins and relatively unhindered internal and alicyclic olefins.6 O-Mesitylenesulfonylhydroxylamine also gave desired amines in comparable yield.7 Alternative procedures for the hydroboration of olefins use commercially available solutions of di-borane in tetrahydrofuran8 or dimethylsulfide.9... 

The order of reactivities of various functional groups determined under standard conditions (using externally generated diborane, and tetrahydrofuran as solvent) is acid > alkene > ketone > nitrile > epoxide > ester > acid chloride.33 Acids, aldehydes, ketones, epoxides, nitriles, lactones and azo compounds are reduced rapidly, esters more slowly and chloral, acid chlorides and nitro compounds are inert. Double bonds undergo the hydroboration reaction,25 nitriles and azo compounds are reduced to amines, and the remaining groups to alcohols. Ketones can be reduced selectively in the presence of epoxides. Contrary to the order of reactivities given above, it has been claimed that nitriles are reduced more rapidly than ketones.223... 

The resultant sulfate ester can be converted to the alcohol by acid hydrolysis. If an acid-sensitive group is present, this hydrolysis is still successful through use of a catalytic amount of sulfuric acid in the presence of 0.5-1.0 equivalents of water with tetrahydrofuran as solvent. The use of base in the formation of the cyclic sulfates themselves can also alleviate problems associated with acid-sensitive groups.174175... 

Pascoe studied the selective hydrogenation of isomeric bromonitrobenzenes to bro-moanilines with commercially available 5% Pt-C-S, 5% Pt-C, 5% Rh-C, and Raney Ni in ethanol or tetrahydrofuran as solvent at room temperature and 0.41 or 10.3 MPa H2 but without any inhibitor.108 In general, 5% Rh-C gave good yields in the hydrogenation of the three isomers with minimum debromination, and 5% Pt-C was effective for the hydrogenation of the ortho and para isomers. Debromination was lesser in tetrahydrofuran than in ethanol for the ortho and para isomers, while ethanol was the preferred solvent for the met a isomer. For the para isomer in tetrahydrofuran, 5%... 

Spescha et al. [4] used the copper complex 6, which was obtained from a thioglucofuranose derivative, as catalyst for 1,4-additions of Grignard reagents to 3, and observed enantioselectivities of up to 60 % ee. The dihydrooxazolylthiophenolato copper complex 7 was employed by Pfaltz et al. 5] for the enantioselective catalysis of Michael additions to cyclic enones the best results were obtained with tetrahydrofuran as solvent and HMPA as additive. There was a pronounced dependence of the stereoselectivity on the ring size of the substrate 16-37 % ee for 2-cyclopente-none, 60-72 % ee for 3, and 83-87 % ee for 2-cycloheptenone. Alexakis et al. [6] used the heterocycle 8, which is readily accessible from... 

The regioselectivity of the iodolactonization of l,6-hcptadicnc-4-carboxylic acid derivatives24 is strongly affected by electronic factors. In fact, the electronic control, as a consequence of the differential alkene substitution, was proven in the iodolactonization of 2-methyl-l,6-heptadi-ene-4-carboxylic acid and 2-methyl-l,6-octadiene-4-earboxylie acid. The conditions employed play an important role in the selectivity low temperature, tetrahydrofuran as solvent and butyllithium as base strongly increase the trans/cis selectivity in favor of the methallyl moiety. 

The following procedure, using tetrahydrofuran as solvent, is simpler and gives a higher yield of product (85%) than earlier methods. Complete removal of excess magnesium is essential to avoid the formation of hexaphenyl-digermane as a by-product. 

As the first transition metal-based homogeneous catalysis of hydroamination, in the early 1970s Coulson from the Du Pont laboratories had described the addition of secondary aliphatic amines to ethylene in the presence of various rhodium compounds [15, 16]. Definite results were reported with RhCl3 3 H2O as pre-catalyst in tetrahydrofuran as solvent under starting ethylene pressures of 5-14 MPa at 180-200 °C for different secondary amines (Table 3). 

In the original procedure Wadsworth and Emmons used sodium hydride as base and 1,2-dimethoxyethane as solvent. In a Japanese procedure sodium amide is used as base and tetrahydrofurane as solvent. The reagent reacts with steroids having a keto group at C3, Cn, or Cio and is thus less selective than triethylphosphonoacetate,... 

Solvent effect. Runge found it possible to convert chloromethyl methyl ether into its Grignard derivative in methylal or tetrahydrofurane as solvent. Methylal... 

Previously limited to condensation with aromatic aldehydes, the reaction of hippuric acid has been applied to aliphatic aldehydes by use of tetrahydrofurane as solvent and substitution of lead acetate for sodium acetate. ... 

The reagent is selective toward ketosteroids. 3-Ketosteroids and A -3-keto-steroids react readily, but keto groups at Ce, C7, and C, are unreactive to the reagent. Japanese workers have used sodium amide as base and tetrahydrofurane as solvent. ... 

With tetrahydrofurane as solvent, zinc turnings made from electrolytic zinc can be used to form reactive organometallic reagents from allyl bromide and propargyl bromide similar to Grignard reagents." For example, reaction of allyl bromide with an equivalent amount of sine in THF, followed by addition of acetone, affords dimethylallylcarbinol in the good yield. 

An interesting extension of this picture is provided by the behavior of p-xylylene dibromide ( 2) With butadiene as monomer and tetrahydrofuran as solvent, their reaction on metallic lithium leads to an unusual co-polymer,... 

The reduction of Mn2(CO)io proceeds smoothly under an inert atmosphere, usually in tetrahydrofuran as solvent, yielding only the corresponding pentacarbonylmanga-nate( -1) anion . Synthesis of the [Re(CO)5] anion is more critical and the product is frequently contaminated by other carbonylrhenates. Reduction of Re2(CO)io by Na/Hg in dimethyl ether yields pure Na[Re(CO)5], whereas in tetrahydrofuran the solvated species Na[Re(CO)5] n(thf), is obtained. 

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