Isolation of product

Participation of carbon-carbon double bonds in solvolysis reactions is revealed in some cases by isolation of products with new carbon-carbon [Pg.313]

The reaction mixture becomes homogeneous and turns deep red-brown shortly after the addition of the a-bromoester. The deep color is, presumably, due to nitrosated phloroglucinol however, this in no way interferes with subsequent isolation of product. 

The isolation of product is usually possible after evaporation of the solvent and extraction with hexane, ether, or toluene. Supported versions, for example on polystyrene grafted with PPh2 groups, have proved unsatisfactory because the rate of deactivation is greatly enhanced under these conditions [37]. Asymmetric versions exist, but the ee-values tend to be lower than in the Rh series [38]. With acid to neutralize the basic N lone pair, imine reduction is fast. Should it be necessary to remove the catalyst from solutions in order to isolate a strictly metal-free product, a resin containing a thiol group should prove satisfactory. A thiol group in the substrate deactivates the catalyst, however. 

Irradiation at >320 nm releases from the polymer, whether insoluble or water-soluble, free oligosaccharides in very high yields. A simple illustration of such a sequence carried out with either insoluble 2-aminoethyl-substituted poly(acrylamide) beads or with water-soluble, substituted poly(vinyl alcohol) is presented in Scheme 9 the isolated overall yield of lactose was 29.9% (soluble-polymer approach). The synthesis on light-sensitive polymers facilitates the isolation of products, which is important from the preparative point of view and as a tool for the study of enzymes, permitting efficient comparison of acceptor specificity and being capable of demonstrating de novo synthesis. 

Isolation of products from homogeneous hydrogenation is more complicated and depends on the catalyst used. 

Isolation of products from the reductions with sodium borohydride is in the majority of cases much simpler. Since the reaction is carried out in aqueous or aqueous-alcoholic solution, extraction with ether is usually sufficient. Acidification of the reaction mixture with dilute mineral acids may precede the extraction. 

In the reductions with borohydrides and boranes the isolation of products differs from that used in the reductions with lithium aluminum hydride, the... 

However, use of a less reactive reagent where [R = R =(CH2)4, (CH2)s, (CH2)20(CH2)2] led to the isolation of products 61 and 62, with a reduction in the yields of the desired cycloadducts. The product 62 arises from Michael addition of the liberated methanethiol to A-methylmaleimide. The protocol was further extended to olefinic dipolarophiles with dimethyl fiimurate, dimethyl maleate, fumaronitrile, and 2-chloroacrylonitrile leading to the corresponding adducts, although these dipolarophiles proved somewhat less reactive with reduced yields being observed. Where applicable, the alkene configuration was reflected in the relative stereochemistry of the cycloadducts (Fig. 3.5). 

Isolation of product from the lactic acid occurs by solvent extraction. 

In addition to alkynes, aldehydes can undergo silylformylation (Equation (27)). Although this reaction pattern was previously carried out with cobalt catalysts, the most important merit in the use of [Rh(cod)Gl]2 or [Rh(GO)2Gl]2 is that the reaction proceeds under far milder conditions. Since such mild conditions make it possible to discriminate starting aldehydes 121 from resultant sterically demanding a-silyloxyaldehydes 122, adjustment of molar ratios of the starting substrates is unnecessary for isolation of product aldehydes. ... 

Expanding the variety and properties of linker groups increases the scope of practical applications of radiation-grafted polymer surfaces for the parallel synthesis of organic compounds. Linker molecules have a bearing on the types of reactions that can be performed and the ease of isolation of products after cleavage. 

The aldehydes and ketones formed in this reaction are subject tn secondary oooden ation reactions, and so the isolation of product nor molly is difficult. However, the reaction of potassium hydroxide in... 

IV. Preparation of Glycofuranosides from Dithioacetals 1. Isolation of Products... 

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