Transform reaction

The alternative approach is to use the computational equivalent of a chemical reaction, or reaction transform. Here, one does not need to define a common template or to generate sets of clipped reagents. Rather, the library can be enumerated using as input the initial reagent structures and the chemical transforms required to operate upon them. In this... 

Comparison of the reaction transform (a) and fragment-marking (b) approaches to the enumeration of izoles. 

There is also a category of intramolecular reactions/transforms which involves total mechanistic stereocontrol with conformationally restricted structures, for example the halolactonization transform 149 150 and the internal cycloaddition 151 152. These... 

Selected additional reactions, transformations, or rearrangements of three-membered ring sulfones and sulfoxides will follow. The criteria for selection is the direct or indirect involvement of the functional groups in the reaction. 

Smaller companies tend to have fewer concerns around, for example, system scalability, global WAN performance, and complex systems integration. They are rather more driven by the pure functionality of the ELN that is addressing the specific scientific disciplines of interest. Key drivers in this sector of the market have been medicinal chemistry departments, where the obvious benefits of searching existing reactions by substructure and reaction transformations, the ability to automate stoichiometry calculations, the ability to load spectral information, etc. have made for easy adoption and clear and realizable benefits. 

Bertz, S.H. (2003) Complexity of Synthetic Reactions. The Use of Complexity Indices to Evaluate Reactions, Transforms and Disconnections. New Journal of Chemistry, 27, 860-869. 

A variant of the Sandmeyer reaction transformed 5-aminoimidazole 3 into the corresponding 5-iodoimidazole 4. Here the diazotization was accomplished using isoamyl nitrite [9,10],... 

The preceding analysis neglects the fact that for very fast follow-up reactions, transformation of B into C may take place within the solvent cage before separation of B and P (Scheme 2.14). The ensuing systematic error is an increasing function of kc but does not exceed +30 mV for rate constants as high as 1011 M-1 s-1.21 Typical examples concern the reductive cleavage of chloro- and bromobenzenes and pyridines.22... 

Palladium(II) is one of the most important transition metals in catalytic oxidations of allenes [1], Scheme 17.1 shows the most common reactions. Transformations involving oxidative addition of palladium(O) to aryl and vinyl halides do not afford an oxidized product and are discussed in previous chapters. The mechanistically very similar reactions, initiated by nucleophilic attack by bromide ion on a (jt-allene)pal-ladium(II) complex, do afford products with higher oxidation state and are discussed below. These reactions proceed via a fairly stable (jt-allyl)palladium intermediate. Mechanistically, the reaction involves three discrete steps (1) generation of the jt-allyl complex from allene, halide ion and palladium(II) [2] (2) occasional isomeriza-... 

We finally consider the EC catalytic mechanism in which the product of the electrode reaction transforms back to the initial electroactive reactant by means of a pseudo first-order chemical reaction [ 15,53,55] ... 

In both soils and water, chemical and biological mediated reactions transform parathion to paraoxon (Alexander, 1981). Parathion was reported to biologically hydrolyze to 4-nitrophenol (hydrolysis product of parathion) in different soils under flooded conditions (Ferris and Lichtenstein, 1980 Sudhakar-Barik and Sethunathan, 1978). 

The calculated hydrolysis half-life at 25 °C and pH 7 is 262 d (Ellington et al., 1988). The hydrolysis half-lives of methomyl in a sterile 1% ethanoEwater solution at 25 °C and pH values of 4.5, 6.0, 7.0, and 8.0 were 56, 54, 38, and 20 wk, respectively (Chapman and Cole, 1982). In both soils and water, chemical- and biological-mediated reactions transformed methomyl into two compounds — a nitrile and a mercaptan (Alexander, 1981). 

Also known as Kostanecki-Robinson reaction. Transformation 1 2 represents an Allan—Robinson reaction (see page 8), whereas 1 3 is a Kostanecki (acylation) reaction ... 

The decay constant of the first-order reaction transforming into °Ar is 10 <2 (89.3%), and the j3 decay constant producing °Ca is... 

The chemistry of nitro compounds forms the basis of a number of well-known processes, such as the Henry or the Nef reactions . Transformations such as the latter permit the interconversion between nitro and other functional groups and are therefore of prime importance. The most commonly employed methods for the reduction of primary nitroalkanes to oximes involve the use of BusSnH, Se/NaBH4, CS2 or SnCla (often in combination with thiophenol) . 

Enumeration is the computational equivalent of carrying out a combinatorial synthesis. The result is a virtual library of product molecules that can then be analyzed using a library design program to select compounds of interest. Two different approaches to library enumeration have been developed fragment marking and the reaction-transform approach (14). 

The reaction-transform approach is based on a computer-readable representation of the reaction mechanism that describes the transformation of the atoms in the reactants to the product. The transform is applied to the input reactants themselves to generate the products. The reaction-transform approach thus more closely mimics the actual synthetic process however, it can be difficult to construct efficient transforms. This is the approach used in the ADEPT software (14). 

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