Workup of reactions

ILs have also been used as inert additives to stabilize transition metal catalysts during evaporative workup of reactions in organic solvent systems [35,36]. The non-... 

Acetone. Readily forms explosive dimeric and trimeric peroxides with acetone, which have resulted in explosions during workup of reactions run in acetone8 9 acetone should not be used as solvent for peroxide oxidations.8,10... 

Thus, in the fine chemicals industry, reduction of ketones and aldehydes relies mainly on the use of complex metal hydrides that require time-consuming workup of reaction mixtures and produce significant amounts of inorganic and organic wastes. Similarly, the oxidation of alcohols into carbonyls is traditionally performed with stoichiometric inorganic oxidants, notably Cr(VI) reagents or a catalyst in combination with a stoichiometric oxidant [1]. 

Also, the addition of surfactants leads to the decrease of surface tension, and thus to an increase of the interfadal area at intense stirring of the mixture. Such a forced dispersion may greatly facilitate mass transfer between phases, which is likely to be the most important factor accounting for the effect of surfactants in heterogeneous process. However, depending on the choice of surfactant the emulsification may ensue, which may strongly interfere with workup of reaction mixtures. 

Workup of the complex reaction mixture was difficult and expensive. As a result, these surfactants have been withdrawn from the U.S. market. In Europe, Hoechst AG produces secondary alkanesulfonates by a similar reaction (eq. 12) ... 

In comparison with manganese dioxide, the DDQ reagent has several advantages for the oxidation of allylic alcohols. The quinone method is more reproducible only one equivalent of oxidant need be added and generally fewer side reactions are observed. On the other hand, the workup of DDQ reactions often requires chromatography and in the simpler cases lower isolated yields may be realized. 

The reactivity of the chloromethyl group is illustrated by the reaction of 2,5-dimethyl-3,4-dichloromethylthiophene (174) with water, which gives (175) Another example of ether formation, is the formation of (176) upon normal acidic workup of the reaction product from 2-thiophenemagnesium bromide and 2-thiophenaldehyde. With... 

Upon heating of a carboxylic ester 1 with sodium in an inert solvent, a condensation reaction can take place to yield a a-hydroxy ketone 2 after hydrolytic workup. " This reaction is called Acyloin condensation, named after the products thus obtained. It works well with alkanoic acid esters. For the synthesis of the corresponding products with aryl substituents (R = aryl), the Benzoin condensation of aromatic aldehydes is usually applied. 

In most cases homogeneous chiral catalysts afford higher enantioselectivities than heterogenous catalysts. Nevertheless, the development of heterogeneous chiral catalysts has attracted increasing interest because workup of the reaction, and recovery of often valuable chiral auxiliaries by simple filtration, is more convenient than in the case of homogeneous catalysts. 

Although it is claimed that the Strecker reaction of 2 results in the exclusive formation of one isomer of 3 and that selective elimination of the minor isomer during isolation of the intermediate compound 4 is not possible, it is apparent that during the workup of the hydrolysis product 4, fractional precipitation or crystallization or other separation of the diastereomers may... 

The paraffin wax is oxidized by air in a liquid phase process at 110-130°C. Catalysts for this radical reaction are cobalt or manganese salts [54]. The quality of the obtained mixture of homologous carboxylic acids is impaired by numerous byproducts such as aldehydes, ketones, lactones, esters, dicarboxylic acids, and other compounds. These are formed despite a partial conversion of the paraffin and necessitate an expensive workup of the reaction product [50,55]. 

It should be noted that the selective reduction of phenylacetylene and diphenylacetylene to either the ds-alkene or the alkane was achieved using LiAlH4 in the presence of FeCk or NiCk as a catalyst [90, 91]. However, deuterolytic workup of the reaction mixtures gave deuterium incorporations <26%, indicating that these reagent systems are not well suited for the synthesis of vinyl- or alkylaluminum compounds from alkynes. 

Analysis of soluble Pd by ICP. A series of reactions was initiated according to the procedure described above. After 20 s, 1 min, 3 min or 1 h, the hot reaction mixture was passed quickly through a 0.45 pm syringe filter to remove solid BaCei cPd c03.x, then the solvent was removed under reduced pressure. A mixture of BaCei cPdx03. cand K2CO3 in IPA/H2O, heated at 80 °C for 1 h, was subjected to the same workup procedure. Each of the solid residues was suspended in 12 mL 10 M aqueous HCl. The mixtures were filtered to produce clear solutions for subsequent analysis on a Thermo Jarrell Ash (TJA) High Resolution ICP spectrometer. A ICP standard solution of Pd (Aldrich) was diluted to 10 ppm for use as the high standard. 

The 10-57-5-hydridosiliconate ion 62 is known in association with lithium,323 tetrabutylammonium,101 and bis(phosphoranyl)iminium93 cations. It is synthesized by hydride addition to the 8-.S7-4-silane 63, which is derived from hexafluoroacetone.101 Benzaldehyde and related aryl aldehydes are reduced by solutions of 62 in dichloromethane at room temperature101 or in tetrahydrofuran at 0°96 within two hours. The alkyl aldehyde, 1-nonanal, is also reduced by 62 in tetrahydrofuran at O0.96 Good to excellent yields of the respective alcohols are obtained following hydrolytic workup. The reactions are not accelerated by addition of excess lithium chloride,96 but neutral 63 catalyzes the reaction, apparently through complexation of its silicon center with the carbonyl oxygen prior to delivery of hydride from 62.101... 

In the instances of phosphorous and phosphonous acid systems, the generation of a new C-P bond via the classical Michaelis-Arbuzov reactions as noted above leads to products that are esters themselves. Isolation of the free acid product requires cleavage of the ester linkage in a separate reaction step, generally after isolation and purification of the initial product. The advent of silyl phosphorus reagents for the Michaelis-Arbuzov reaction allowed free acid products to be isolated simply by water workup of the reaction system. Further, since the byproduct was a silyl-halide, the general concern that the by-product halide would participate in an extraneous Michaelis-Arbuzov reaction was obviated. 

W(CO)6 in toluene at room temperature gave the tricyclic adduct 190a in 94% yield after acidic workup. This reaction forms the tungsten-containing azomethine ylide 191, which undergoes the [3 + 2]-cycloaddition with 189a. The rhodium(n)-catalyzed cyclization of the ene-yne-aldimine 192 with alkene 193 into the cyclopropane 194 was reported by Uemura and Ohe (Scheme 32).42c... 

Reiter and co-workers found in the course of their extended research on fused [l,2,4]triazines <1994JHC997> that the N-protected methylthiotriazine derivative 110 when reacted with carbon disulfide under strongly basic conditions yields a mixture of two products 111 and 112. When this mixture was treated with dibromomethane, product 113 was easily removed from the reaction mixture, and workup of the mother liquor allowed the isolation of the [l,2,4]triazolo[l,5-c][l,3,5]thiadiazine derivative 114 in 49% yield (Scheme 21). The same authors carried out ring closure of the ring-closed semithiocarbazide 115 to the triazolothiadiazine derivative 118 as shown in Scheme 21 <1997JHC1575>. The starting compound was treated with triethyl orthoformiate. The authors assume that first intermediate 116 is formed which cyclizes to a second intermediate 117 and, finally, ethanol elimination yields the isolated product 118. 

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