Intermediates from ring-opening reactions. Reactions of 2-chloro-5-nitropyridine and 2-chloro-3-nitropyridine with deuteroxide ion in selected solvents

Abstract

Open chain intermediates from the ring-opening reaction of aqueous sodium deuteroxide (2 mol) with 2-chloro-5-nitropyridine (1 mol) and 2-chloro-3-nitropyridine (1 mol) were isolated. These intermediates were purified, analyzed for elemental composition, and characterized by various spectrophotometric techniques. The intermediate formed from 2-chloro-5-nitropyridine and two equivalents of deuteroxide ion reacts with additional deuteroxide in D2O in various polar solvents to reclose the pyridine ring. The kinetics of the ring closure reaction are reported and are supplemented with observations of salt and solvent effects upon the rate of closure. In addition, a mechanism for the ring closure is presented. The intermediate formed from 2-chloro-3-nitropyridine did not undergo a similar ring closure when reacted with additional deuteroxide, but instead formed various decomposition products. A reason for the failure of this ring closure is suggested.

Solvent effect on the alkaline hydrolysis of 2‐thiophenyl‐ 3,5‐dinitropyridine

“…Thus the present study shows that the increase in the rate in the case of DMSO and dioxane except AN may be due to the increase in hydrogen bond acceptor property of the medium. Although AN-H 2 O mixture is considered as HBA, it shows the lowest value of k presumably due to AN-H 2 O tended to separate into layer [42]. On the other hand, the decrease in rate in the case of hydroxylic solvents such as MeOH, EtOH except iPrOH, is attributed to the interaction between solvent and reactant through hydrogen bond donor property of the medium.…”

S N Ar Reactions of Amines in Aprotic Solvents

“…These reactions are commonly referred to as S N (ANRORC) because they are promoted by initial addition of the nucleophile (AN) at an activated unsubstituted carbon 1a,13 . Evidence has been provided that this mechanism can operate to a large extent in the substitution of halonitropyridines by strong nucleophiles like OH in water/DMSO mixtures rich in DMSO, or with amide ions in ammonia 14 16 . The identification of the open intermediates 16 constitutes a strong indication to suggest that the conversion of 2-halo-5-nitropyridines into the corresponding 2-hydroxypyridines occurs via the S N (ANRORC)-type process rather than via the anticipated S N Ar mechanism.…”

“…Evidence has been provided that this mechanism can operate to a large extent in the substitution of halonitropyridines by strong nucleophiles like OH in water/DMSO mixtures rich in DMSO, or with amide ions in ammonia 14 16 . The identification of the open intermediates 16 constitutes a strong indication to suggest that the conversion of 2-halo-5-nitropyridines into the corresponding 2-hydroxypyridines occurs via the S N (ANRORC)-type process rather than via the anticipated S N Ar mechanism. The feasibility of nucleophilic substitutions at the 4-or 7-position in condensed heterocycles such as nitrobenzofurazans has been also recently proved, and the finding of -adducts of the type found in trinitrobenzene analogues gives strong support to the operation of similar mechanisms 17 .…”

Ring opening of pyridines: the pseudo-cisand pseudo-transisomers of tetra-n-butylammonium 4-nitro-5-oxo-2-pentenenitrilate

“…During the 1980s, Reinheimer et al (1980Reinheimer et al ( , 1984 investigated the reaction of 2-chloro-5-nitropyridine with an excess of sodium hydroxide in dimethyl sulfoxide/water solutions. Using visible spectroscopy, in addition to 1 H and 13 C NMR, they were able to show that a relatively stable intermediate was formed.…”