Through /3-elimination

Upon addition of a base—triethylamine is often used—the sulfonium salt 7 is deprotonated to give a sulfonium ylide 8. The latter decomposes into the carbonyl compound 2 and dimethyl sulfide 9 through /3-elimination via a cyclic transition state. 

Addition of PhPdl to the allene triggers cyclopropyl ring opening to generate a cr-palladium species, which readily leads to a 1,3,5-triene through /3-elimination. From the observed diastereoselectivities, the reaction seemingly proceeds stepwise via the well-stabilized zwitterionic intermediate. 

Scheme 122) (78JA1630). Silacyclobutenes also result from the FVP of l,3-bis(trimethyl-silyl)-3-methoxysilylpropenes through /3-elimination of the methoxysilane (Scheme 123) <81JOM(216)C5>. 

Similar to the analysis of ordinary proteins, phosphoproteins also need to be cleaved into small manageable peptide fragments any one of the proteases listed in Table 1 can be used. The concept of chemical tagging through /3-elimination/Michael addition reactions has been adopted to facilitate the cleavage process. The [3-elimination reaction converts phosphoserine and phosphothreonine to dehydroalanine and... 

Alginate lyase catalyzes cleavage of the glycosidic bond through /3-elimination. The similarity between the lyase reaction and the C-5 mannuronan epimerase reaction has been noted. Interestingly, the proteins share little sequence homology. 

The products formed on treatment of various 2-acetamino-2-deoxy-furanoses with alkaline ion-exchange resin have been shown to be the 2,3-unsaturated furanoses (60), formed through 3-elimination of C-3 hydroxy, alkoxy, or tetrahydropyranyloxy substituents, rather than... 

Acidic or alkaline hydrolysis of protein can yield a-keto acids through 3-elimination of a water molecule ... 

Fig. 4. Synthesis of estrone (20) through elimination of unactivated 19-methyl group via intramolecular functionalization of C-19. -TsOH...

The fatty acids obtained from the process can be used directly or further manipulated for improved or modified performance and stabiUty. Hardening is an operation in which some fraction of the unsaturated bonds present in the fatty acids are eliminated through hydrogenation or the addition of H2 across a carbon—carbon double bond. This process was initially intended to improve the odor and color stabiUty of fatty acids through elimination of the polyunsaturated species. However, with the growth in the use of specialty fatty acids, hydrogenation is a commercially important process to modify the physical properties of the fatty acids. 

A slight generalization of the reasoning shows that all equations, which are derived from (2.26) or (2.27) through elimination of some of the terms on the right-hand side which are not identical to x, reduce to generating functions of easily characterizable types of planted trees. ... 

The presence of PCHE in the HDN product (Table 1) indicates that at least part of the HDN reaction of PCHA proceeds through elimination of ammonia rather than by direct hydrogenolysis. Nevertheless, the direct product of the elimination reaction (allylcyclohexylamine) was not observed. This must be due to its strong adsorption and fast hydrogenation to PCHA. 

In contrast with the relatively facile thermal rearrangement of sulfinates to sulfones discussed in the preceding section, the reverse process is relatively, rarely encountered and is usually observed only at elevated temperatures. One of the first thermal sulfone to sulfinate isomerizations has been invoked by Fields and Meyerson to occur during the pyrolysis of dibenzothiophene S, S-dioxide (26) to dibenzofuran, through elimination of sulfur monoxide from the sultine intermediate 27 (equation 27). More recently, the flash vapor-phase pyrolysis of various 2,5-dialkyl and diaryl thiophene-S, S-dioxides has also been shown to involve SO extrusion and formation of the corresponding furans in good yields . 

Heparinase and heparanase are lyases, that is, they cleave glycosidic linkages through elimination of water molecules. This cleavage, which occurs in a random, endolytic mode,243 between an aminohexosyl and a... 

Aldoximes are readily dehydrated with N, N -carbonyldiimidazole (CDI). An intermediate azolide is formed in the process under elimination of one mole of imidazole, which fragments into a nitrile through elimination of CO2 and a second mole of imid-azole.[1],[2]... 

To this must be added the 10% to 20% savings in direct lab productivity to be achieved through elimination of repetitive clerical work and through computerization of inefficient and error prone manual procedures. 

The trimethylsilyl ethers 212 of four-membered 1-alkenyl-1-cyclobutanols rearrange to the ring-expanded 0-mercuriocyclopentanones 213. These can be converted into the a-methylenecyclopentanones 214 through elimination or further expanded by one-carbon atom into cyclohexanones 215 via the Bu3SnH-mediated free radical chain reactions [116]. A similar radical intermediate is suggested to be involved in the ring expansion of a-bromomethyl-fi-keto esters [117]. (Scheme 84)... 

The third approach (path c) requires that a chain containing at least two carbon atoms be present in AN. As a mle, AN can be smoothly transformed into ene nitroso acetals B, which (like standard enamines) can react with electrophiles to give the target nitronates through elimination of the Si+ fragment (for more details, see Section 3.5.4). 

Consider a trialkoxysilane as co-precursor for an initial 1 1 mixture of alkoxysilane and organoalkoxysilane, and recall that in the case of ORMOSIL condensation takes place only through elimination of water27 and not by alcohol formation. The mechanism involves hydrolysis and condensation reactions ... 

On the other hand, bisallene 13 having a two-carbon tether underwent dimerization at the terminal carbon-carbon double bonds at lower temperature. Aromatic compound 14 was ultimately formed through elimination and a hydrogen shift [12]. 

In the case of unsaturated chloramines 209, the DTBB-catalyzed lithiation had to be carried out in the presence of the electrophile in THF at —78 °C in order to avoid decomposition of the corresponding functionalized organolithium intermediate through elimination reactions. Final hydrolysis yielded a mixture (variable ratios 11.5/1 to 1/19 depending on the electrophile) of the a- and y-products 210 (Scheme 72) . ... 

Base the maintenance dose upon the percentage of the peak body stores lost each day through elimination. The following formula has had wide clinical use ... 

The toxicity of fluoroacetic acid and of its derivatives has played an historical decisive role at the conceptual level. Indeed, it demonstrates that a fluorinated analogue of a natural substrate could have an activity profile that is far different from that of the nonfluorinated parent compound. The toxicity of fluoroacetic acid is due to its ability to block the citric acid cycle (Krebs cycle), which is an essential process of the respiratory chain. The fluoroacetate is transformed in vivo into 2-fluorocitrate by the citrate synthase. It is generally admitted that aconitase (the enzyme that performs the following step of the Krebs cycle) is inhibited by 2-fluorocitrate the formation of aconitate through elimination of the water molecule is a priori impossible from this substrate analogue (Figure 7.1). 

The first dehydration products formed by general, acid-base catalysis are represented by the enolic forms (7, 9, and 10) of the deoxydicarbonyl sugars 7a, 9a, and 10a. The enolic compounds are formed from enediols by the removal of a molecule of water through -elimination of a hydroxyl group. For example, from the 1,2-enediol (6) derived from D-glucose or D-fructose, the enolic form (7)of3-deoxy-D-eryf/iro-hexosulose (7a) is produced, whereas from the 2,3-enediol... 

The 1,4-addition of sp3-geminated organodimetal compounds, prepared by the Gaude-mar/Normant coupling reaction, to alkylidenemalonate gives Z-alkene selectively through elimination of the malonate moiety (equation 33)56,57. 

Considerably reduced investment and operating costs. This has been brought about mainly through elimination of multiple reactors and accessory equipment, elimination of time cycle controllers, greatly simplified method of regeneration, and elimination of reheat furnaces. 

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