Nonreductive

A large variety of methods is applicable to the formation of isolated double bonds. This permits selection of reagents compatible with other functionality present. Alcohol dehydration, ester elimination and other nonreductive p eliminations are the most common methods. Reductive elimination of halo-hydrins, vic-dihalides, etc., and of a variety of ketone derivatives has also been used. 

In the modified procedure one of several heteroaromatic sulfones is used. The crucial role of the heterocyclic ring is to provide a nonreductive mechanism for the elimination step, which occurs by an addition-elimination mechanism that results in fragmentation to the alkene. The original example used a benzothiazole ring,279 but more recently tetrazoles have been developed for this purpose.280... 

The excess aluminum in the charge compensates for the loss of aluminum due to nonreductive air oxidation, and also provides aluminum for alloying with the niobium metal produced in the reduction. As mentioned earlier, the liquidus temperatures of niobium-aluminum alloys are lower than the melting point of niobium. The melting of this alloy and the alumina slag is achieved even with the reduced amount of heat available from the reaction implemented without preheating in the open reactor. 

Figure 2. Solubilities and molecular weights of a vitrinite (80.8% C, daf) after nonreductive ethylation (yields calculated on ethylated product (daf))...

The unexpected formation of cyclopenta[b]indole 3-339 and cyclohepta[b]indole derivatives has been observed by Bennasar and coworkers when a mixture of 2-in-dolylselenoester 3-333 and different alkene acceptors (e. g., 3-335) was subjected to nonreductive radical conditions (hexabutylditin, benzene, irradiation or TTMSS, AIBN) [132]. The process can be explained by considering the initial formation of acyl radical 3-334, which carries out an intermolecular radical addition onto the alkene 3-335, generating intermediate 3-336 (Scheme 3.81). Subsequent 5-erafo-trig cyclization leads to the formation of indoline radical 3-337, which finally is oxidized via an unknown mechanism (the involvement of AIBN with 3-338 as intermediate is proposed) to give the indole derivative 3-339. 

My intention here is not to recall horror tales from the crypt , the extremes to which reductionists may threaten, malign, sensor, and censure scientists pursuing nonreductive alternatives to monophyly. Rather, I will show how polyphylism can flesh out evolutionary skeletons and prepare the way for modeling evolution itself. 

Forsman W.C., Mertwoy H.E., Wessbecher D.E. Nonreductive spontaneous deintercalation of graphite nitrate. Carbon 1988 26 693-699. 

Several nonreductive methods for cleavage of benzyl groups have also been developed. Treatment with s-butyllithium, followed by reaction with trimethyl borate and then hydrogen peroxide, liberates the alcohol.24 The lithiated ether forms an alkyl boronate, which is oxidized as discussed in Section 4.9.2. 

Table 13.7 Kinetic Data on Nucleophilic Substitution and Nonreductive Elimination (Dehydrohalogenation) Reactions of Some Polyhalogenated Hydrocarbons in Aqueous Solution at 25 °C ... 

A number of attempts have been made over the years to develop reproducible synthetic routes to six- and seven-coordinate isocyanide complexes of molybdenum and tungsten. Two of the older methods, namely, the reaction of the hexacarbonyls with halogens in the presence of an isocyanide (775,116) or reactions of the salt Ag4Mo(CN)8 with isocyanides (74), have given six- and seven-coordinate products. Recently, however, the discovery of the reductive or nonreductive cleavage of multiple metal - metal bonds in dinuclear group VIA compounds by isocyanides has provided a facile route to the synthesis of a variety of homoleptic and related isocyanide complexes of these metals in reasonable yields. 

M. V. Novotny, Y. Huang, and Y. Mechref, Microscale nonreductive release of O-linked glycans for subsequent analysis through MALDI mass spectrometry and capillary electrophoresis, Anal. Chem., 73 (2001) 6063-6069. 

Perchlorate, (i) Action of heat and test for chloride (IV.22, 7), and nonreduction with NaN02 or FeS04 in acid solution (IV.22, 5). 

Nonreductive syntheses of 3-piperideines from pyridine derivatives are not numerous. For example, treatment of 3-methylpyridine with o-tolyllithium was reported to give a mixture of 2-o-tolyl-3-methyl-3-piperideine (45) and three isomeric methyl o-tolylpyridines, formed by disproportionation of the dihydro intermediates.38... 

When the benzene-insoluble residue obtained at 200° C was subjected to nonreductive alkylation (33) the solubility was restored to 80%, and this strongly implies that the generation of new functional groups is responsible for the lower solubility at this temperature. However, in view of inter- or intramolecular alkylations that may accompany the cleavage reactions, it is not possible to correlate the extent of degradation with changes in the molecular weights. 

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