REACTIONS OF THE ANIONS

One of the most versatile methods for the synthesis of derivatives with the acetylene or cumulene system consists In deprotonatlon of the starting acetylene or cumulene and subsequent reaction of the anionic or organometal1ic intermediate with an electrophilic reagent. 

Alternatively, various 4-substituted derivatives have been prepared via synthesis of amino acid (68) by reaction of the anion formed from protected glycine and an appropriately substituted Schiff base. 

This group is prepared by the reaction of the anion of 9-hydroxyanthracene and the tosylate of an alcohol. Since the formation of this group requires an S 2 displacement on the alcohol to be protected, it is best suited for primaiy alcohols. It is cleaved by a novel singlet oxygen reaction followed by reduction of the endo-peroxide with hydrogen and Raney nickel. 

Several methods for the preparation of unsymmetrical sulfur diimides RN=S=NR have been developed. One approach involves the addition of a catalytic amount of an alkali metal to a mixture of two symmetrical sulfur diimides, RN=S=NR and RT8i=S=NR. A second method makes use of alkali-metal derivatives of [RNSN] anions.Eor example, derivatives in which one of the substituents is a fluoroheteroaryl group can be prepared by the reaction of the anionic nucleophile [RN=S=N] with pentafluoropyridine. Sulfur diimides of the type RN=S=NH (R = 2,4,6- Bu3C6H2S) have also been prepared. "... 

Benzyl chloride can be converted into benzaldebyde by treatment with nitromethane and base. The reaction involves initial conversion of nilro-methane into its anion, followed by SN2 reaction of the anion with benzyl chloride and subsequent E2 reaction. Write the mechanism in detail, using curved arrows to indicate the electron flow in each step. 

The reaction of the anion of an aryl allyl sulfoxide with benzaldehyde can take place via an a or y attack. The a attack leads to a product with three stercogcnic centers (four possible diastereomers) whereas the y attack results in a product which has only two stereogenie centers and geometric isomerism is possible. 

High, simple diastereoselection was also observed on the reaction of the anion of racemic (Z)-1-(phenylsulfinyl)-2-butene (2 equiv) with a nonracemic bicyclic chiral enone (1 equiv) giving a 7-1,4-adduct in 82% eeI5b. 

Schneider and Simon82 prepared / -ketosulfoxides 47a and 47b by sulfinylation of the dianions of the methyl acetoacetates 48a and 48b with sulfinate ester 19 followed by decarboxylation of the intermediate products (Scheme 2). Apparently this avoids racemiz-ation experienced by others in the direct synthesis of these compounds9. /J-Ketosulfoxides are also available from the reaction of the anion derived from methyl p-tolyl sulfoxide with esters (see Section II.E). They can also be obtained, in some cases, through the hydrolysis of a-sulfinylhydrazones whose synthesis is described below. Mention has already been made of the synthesis of 2-p-tolylsulfinylcycloalkanones such as 32. 

J.I3 Na As04 is a salt of a weak base that can accept more than one proton, (a) Write the chemical equations for the sequential proton transfer reactions of the anion with water. Identify the acid and the base in each reaction, (b) If 35.0 g of Na3As04 is dissolved in water to make 250.0 ml. of solution, how many moles of sodium cations are in the solution ... 

The pH of the aqueous solution of an amphiprotic salt is equal to the average of the pKlts of the salt and its conjugate acid. The pH of a solution of a salt of the final conjugate base of a polyprotic acid is found from the reaction of the anion with water. 

Reaction of the anion derived from the tosyl imide of l,3,S-trithiane with alkyl iodides gives a mixture of the mono- and di- alkylated products, in which anti stereochemistry predominates. The analogous 1,3-dithiane derivative is only monoalkylated <96JCS(P1)313>. 

Adding these two equations gives the reaction of the anion with itself, and as we show in Chapter 16, when equiiibria are added their equiiibrium constants are multiplied. Thus ... 

The cis configuration of 96 was elucidated by X-ray structure analysis. The data suggest that the cyclization reaction of the anion 95 generated from 94 to 91a proceeds stereoselectively in the solid state [16]. 

The reaction of the anionic gold(I) complex PPN[Au(C6F5)Cl] with [MeSi Me2SiN (p-tol) 3SnLi(OEt2)] leads to formation of an anionic complex with a Sn—An bond, shown in Equation 3.8, whose P H NMR spectrum shows a singlet at 47.5 ppm [81]. 

Doubts have recently been expressed regarding the validity of the metaphosphate pathway for hydrolysis of the monoanion of 2,4-dinitrophenyl phosphate (111) 70,71,72) since the basicity of the 2,4-dinitrophenolate group is insufficient to produce a zwitterion corresponding to 106 or even a proton transfer via intermediates of type 103 or 105 (pKa values in water 4.07 for 2,4-dinitrophenol, 1.0 and 4.6 for 2,4-dinitrophenyl phosphate). Instead, hydrolysis and phosphorylation reactions of the anion 111 are formulated via oxyphosphorane intermediates according to 114. 

Even fully substituted aromatic compounds can be prepared utilizing the Mi-chael/Dieckmann strategy. As reported by Covarrubias-Zuniga and coworkers (Scheme 2.32) [67], reaction of the anion of l-allyl-l,3-acetonedicarboxylate (2-138) and the ynal 2-139 afforded the intermediate 2-140 which led to the resorcinol 2-142 with spontaneous aromatization under acidic conditions via 2-141 in an overall yield of 32 %. 2-142 was transformed into mycophenolic acid (2-143) in only a few additional steps [68]. 

Alkyl mercury halides participate in a photo-stimulated radical chain reaction of the anion of nitroalkanes (see Eq. 5.38) in which a 275-W sun lamp is used.56 c Primary, secondary, and tertiary alkyl radicals generated from alkyl mercury halides react with the anion of nitroalkanes to form new C-C bonds. 

O-as- S p i ro p h os p h or a n e s 69, which display anti-apicophilicty, exhibit enhanced reactivity toward nucleophiles compared to 0-/ra r-spirophosphoranes 70 for example 69 produces hexacoordinate 157 on treatment with MeLi at 0°C while 70 is unreactive under the same conditions (Scheme 16). Compound 69 (R = Bn) is more reactive toward bases than 70 (R = Bn) with KHMDS deprotonating 69 (R = Bn) in THF at 0 °C but not 70 (R= Bn). -BuLi was sufficiently basic to deprotonate both 69 and 70 <2002JA13154>. Further differences are observed in the stability and stereochemistry of the brominated products formed between the reaction of the anion with BrCF2CF2Br. The effect of the bromide substituent in the O-m-derivative is such that it accelerates pseudorotation to the O-trans-isomer (Scheme 17). 

The reaction of the anion ICHXY with 75 shows a marked solvent dependence60. Addition of nitriles, e.g. CH3CN, suppresses the addition at C1 — sometimes observed as a side reaction (77) — in favor of addition at C3 resulting in triafulvene formation... 

In the ethyl and isopropyl cases, the steepest descent pathway still connects the Sn2-TS to the SN2 products but the formation of ET products along the bifurcation in the indirect ET pathway is expected to increase. These trends are likely to be at the origin of the stereochemistry of the reaction of the anion radical of anthracene with optically active 2-octyl halides recalled at the beginning of this section. 

The Michael-type reaction of an anion (generated from compound 77) with ethyl crotonate yielded the corresponding ester 78 in 82% yield (Scheme 19). Alkylation of compound 77 with benzyl bromide afforded derivative 79 in 85% yield. The attempted reactions of the anion with oxiranes and trimethylsilyl chloride did not lead to the expected substitution products and the starting oxadiazoles were recovered in 70-80% yields <2001ARK101>. 

Another possibility is the determination of the scavenging ability of 02 by measuring the reaction of the anion with a-ketomethiolbutyric acid (KMB) to produce ethane, which is measured by gas chromatography. Fresh and air-dried tomato products were evaluated by this methodology (Lavelli and others 1999 2000). 

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