Direct displacement of the

That is, although we required equal x-direction displacements of the two layers (the proportion of N in each layer was adjusted to create that equal-displacement condition), the lateral displacfiments arfi guitfijjjffer-ent. Those different displacements are a violation of the requireddeToT- mation compatibility of laminae in a laminatir Tolemedy this violation, the top layer must get wider by application of a lateral tensile stress aj, and the bottom layer must get narrower by application of a compressive stress Oy. The two deformations must result in equal-width laminae to satisfy deformation compatibility. Moreover, the lateral stresses in each layer must satisfy force equilibrium in the y-direction, i.e.,... 

Similarly, Cocco and co-workers reported the direct displacement of the thiomethyl group from pyrimidines 52 with hydrazine to produce 53, along with varying amounts of the dihydrazide, a result of the displacement of both the thiomethyl group as well as X (X = alkylamine) <00JHC707>. After optimization, 53 could be produced selectively and then cyclized by heating in butanol to form 54 in excellent yields. 

The small amount of racemization might be due to a certain degree of internal return and/or direct displacement of the tosylate. 

Desilylation may involve initial attack of F on the carbonyl group followed by C to O migration of the silyl group to give QHsCXFJOSKCH-,), or direct displacement of the benzoyl union. 

M. Miljkovic, M. Glicorijvic, and D. Glisin, Steric and electrostatic interactions in reactions of carbohydrates. 111. Direct displacement of the C-2 sulfonate of methyl 4,6-0-benzylidene-3-<9-methyI-2-O-methylsulfonyI-p-D-gluco- and mannopyranosides, J. Org. Chem. 39 3223 (1974). 

Denitro-sulfonylation ally lie sulfones.h2 Two groups have reported that in the presence of this Pd(0) catalyst, allylic nitro compounds (1) undergo denitro-sulfonylation on reaction with C6H5S02Na-2H20 to afford allylic sulfones (2) and (3). The reaction occurs with high regioselectivity to afford the product of direct displacement of the nitro group. 

Adenine aminohydrolase of A. vinelandii does not catalyze the back incorporation of products, hypoxanthine or chloride, into 6-chloropurine during the course of hydrolysis when examined over a wide range of pH in contrast to the back incorporation of oxygen-18 into hypoxanthine catalyzed by adenosine aminohydrolase (80) (see Section III). These results are consistent with a direct displacement of the 6 substituent by water rather than the intermediate formation of purinyl enzyme or chloroenzyme during catalysis. 

Depending on the nature of the substrate, treatment of acid chloride with 8-aminoallylsilane derivatives 91 gives different regioisomers. When R1 is methyl or a primary alkyl group, a normal S reaction takes place. When R1 is the sterically hindered isopropyl group, direct displacement of the silyl group occurs (equation 69)128. Similar regioselectivity is observed when an aldehyde is employed as the electrophile (see Section II.B.6). 

The exchange of the acetate groups of vinyl acetate with those of CD3.C02H, which is catalysed by mercuric acetate, was claimed to involve direct displacement of the vinylic acetate (Samchenko and Rekasheva, 1965), although an electrophilic addition-elimination seems more plausible. 

Direct displacements of the hydroxyl group by azide are uncommon, but carbonium ions derived from alcohols are attacked by the azide ion to give organic azides (43) (Reaction XXVIII). 

Moreover, several mechanisms for the suggested direct displacement of the halide ion from the radical anion by a nucleophile were examined and all were considered unacceptable because of the violation of quantum-mechanical principles or incompatibility with experimental observations64. 

Recognizing that nucleophiles can react at two different sites, an initial thought might be direct displacement of the chloride anion in an Sn2 manner. However, as alluded to in Problem 3(d), nucleophiles can add to carbonyl groups as shown below. 

This apparently simple substitution does not involve a direct displacement of the leaving group in a single step As... 

Allyl Halides. In bimolecular substitutions on allyl halides, direct displacement of the halide ion (S 2) almost always occurs, and conjugate attack (Sn2 ) is rare. It is perhaps significant that the few examples of conjugate reaction... 

The generally accepted mechanism for the amine arylation is shown in Scheme 1. The catalytic cycle begins with the oxidative addition of the aryl halide (or sulfonate) by Pd (0). The palladium (II) aryl amide can be formed either by direct displacement of the halide (or sulfonate) by the amide or via the intermediacy of a palladium (II) alkoxide [19]. Reductive elimination of the C-N bond results in the formation of the desired arylamine and regeneration of the Pd (0) catalyst [lie,20]. 

On the other hand, R2CuLi reacts with 1 mainly by direct displacement of the acetate group (equation II). (CH3)2CuLi reacts with the enyne acetate 2 to give mainly a coupled product 3 (equation III). 

Problem 3.12 A less likely mechanism would be direct displacement of the tosylate anion... 

The a-amidoalkylation reaction, which involves the addition of carbon nucleophiles (primarily aromatic rings, alkenes, cyanides, isocyanides, alkynes, organometallic and active methylene-containing compounds) to substituted amides (89) where X is a leaving group (Scheme 17), has been extensively re-viewed. A variety of organometallic condensations have since been reported which extend the scope of this reaction. The reactive intermediates in these reactions are considered to be N-acylimines (88) or N-acyliminium salts (SKI). Direct displacement of the a-haloalkylamide precursors (89 X = halogen) cannot in certain cases be discounted. 

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