2 - -ethane nucleophillic substitution

The acetoxy group may also be substituted using N-nucleophiles such as pyrrolidine or morpholine. Since the products of nucleophilic substitution are aminals, elimination results in /3-substituted ethane sulfonamides 108. Moreover, while no reaction occurs with phthalimide or sodium azide, trimethylsilyl azide reacts in the presence of Lewis acids such as zinc chloride or tin chloride to give a diazido compound 109 as product (Scheme 32) <1997PHA482>. 

Ligands 179 and 180 were synthesized by the nucleophilic substitution of the sodium glycolate of TV-methyldiethanol amine on either 2,6-dichloropyridine or 2,6-6 (chloromethyl)pyridine. However, 183 and 184 were synthesized by the qua-temization of 181 or 182 with l,2-6is(P-ethoxy)ethane in acetonitrile. In both instances the resulting diquatemary ammonium salts were demethylated by L-Selec-tride in refluxing tetrahydrofuran to afford the desired pyridino coronand. Com-piexation studies have not been performed on any of these coronands and the physical properties of these compounds do not indicate any unusual characteristics m). 

The Sb centre in the structurally characterized complex [H(py)2][Sbl4(dmpe)] (py = pyridine, dmpe=l,2-bis(dimethylphosphino)ethane] shows significant distortions from octahedral geometry which are discussed in terms of an arrested double S 2 transition state for the nucleophilic substitution of two iodine anions by dmpe. ... 

Because of the great versatility of nucleophilic substitution reactions many kinds of products can be prepared from alkyl halides. Table 11.1 lists some common nucleophiles in the approximate order of their reactivity am shows the products of their reactions with bromom ethane. 

Let us look at a typical nucleophilic substitution reaction. Ethyl bromide (bromo-ethane) reacts with hydroxide ion to give ethyl alcohol and bromide ion. ... 

The research on the reaction mechanism of the oxidative polycondensation of 2,6-dimethylphenol (DMP) was also continued in the years around 1990. In several publications a Dutch research group reported on kinetic studies dedicated to the 02-promo ted polycondensation of DMP catalyzed by copper tetramethyl 1,2-diamino-ethane complexes [233-236] or by copper complexes of imidazole [237,238]. The speculative mechanistic scheme was based on dimeric copper complexes such as (147a) which were assumed to incorporate a DMP anion (147b) which was oxidized to yield a phenoxy cation and to coordinate another DMP molecule (148a). The growing step was then assumed to consist of a nucleophilic substitution at the phenoxy cation (149) with liberation of a reduced dimeric copper complex (148b). This complex was believed to be... 

The use of phosphide nucleophiles in an SN2 attack on alkyl-substituted cyclic sulfates allows access to a wide range of phospholane derivatives. However, if aryl-substituted cyclic sulfates are used, elimination and racemization processes compete with substitution. To access bis(2,5-diphe-nylphospholano)ethane (4), an alternative strategy was required (Scheme 13.2).14... 

S)-l is obtained from the bis(methyl carbonate) of (Z)-2-butene-l,4-diol and l,2-bis(tosyl-amino)ethane through a tandem pa]ladium(0)-catalyzed allylic substitution in the presence of (R)-BINAP (I) as chiral ligand79. Equilibration of the 7t-allylpalladium intermediates formed before the intramolecular nucleophilic attack is necessary for high enantioselectivity. Thus, only a racemic piperazine is produced in the reaction of the more nucleophilic l,2-bis(benzyl-amino)ethane with the diacetate of (Z)- or ( )-2-butene-l,4-diol. 

Carbonyl-carbonyl condensation reactions. These reactions involve both a nucleophilic addition step and an a-substitution step. They can occur when two carbonyl compounds react with one another. For example, reaction of two molecules of ethanal. 

Chlorinated terphenyls are reductlvely dechIor1nated, but also undergo substantial photosubstitution In alcohol solvents ( ) In contrast to the low yield of substitution products from PCB. In the terphenyl series photosubstitution is believed to take place by attack of the nucleophile directly on the excited state with concomitant chloride ejection. Alkylated PCB molecules (chloroalkylenes), candidate PCB replacement compounds, exhibit UV electronic spectra nearly Identical to those of PCB yet photodegrade more rapidly (28). Another possible PCB substitute consists of a mixture of bis-(chlorophenyl)ethanes (Iralec) that also undergoes dechlorination and substitution reactions on Irradiation (32). 

Hydration in the presence of mercury(II) sulphate yields an (oxoalkyl) compound (equation The treatment of the phosphonic ester 364 (R = Et, Z= P03Et2) with a thiolate leads, via diethyl ethynylphosphonate, to the ethenylphosphonic diester 365 with the concomitant formation of thiophosphate ester in this particular case, the product 365 as initially formed, is of Z geometry, but isomerizes when distilled . In other cases of the reactions with thiols, for instance with 364 (R = Et, Z = Cl), the direct replacement of Z is accompanied by overall displacement plus addition at each carbon to give products of types 366 (as a mixture of E and Z stereoisomers) and 367. The same substrate 364 (R = Et, Z = Cl) with the monosodium salt of ethane-1,2-diol represents an alternative route (substitution followed by addition) to 361, but with more basic nucleophiles such as Bu O, and even MeO , cleavage of the phosphorus-carbon bond occurs, although the extent of this decreases, and the extent of addition (with EtO and PhO ) increases, when R = Me is replaced by R = Et. The additions of arylsulphenyl chlorides to 364 (R = Et, Z = Me) occur stereoselectively to give only the E products . 

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