Ring Transformation of Pyridines and Benzo Derivatives under the Action of C-Nucleophiles

Abstract

The data on ring transformations of heterocyclic systems containing a pyridine ring on treatment with C-nucleophiles are generalized and described systematically over the period of up to 1999. CONTENTS I. Introduction II. Cyclopentadiene derivatives III. Ketones and enamines 1. Ring transformations of dinitropyridones 2. Ring transformations of nitropyridinium salts into indoles IV. β-Dicarbonyl compounds and carboxylic acids V. Nitroalkanes and sulfoxides VI. Conclusion I. INTRODUCTIONPyridine ring is relatively stable against cleavage, although it is less stable than benzene.The Zincke-König reaction, 1 i.e. cleavage of the quaternized pyridine ring on treatment with aromatic amines to give glutaconic dialdehyde dianils, was historically the first comprehensively studied example of this type of reaction. Subsequently, numerous ring transformations of the pyridine ring induced by nucleophiles have been discovered and studied. 2 They include, first of all, a number of new rearrangements some of which are general for the chemistry of heterocyclic compounds, such as the amidine rearrangement 3 and the enamine rearrangement of pyridine derivatives found in our study. 4 Nevertheless, no comprehensive and special review on ring transformations of the pyridine ring induced by C-nucleophiles have been published so far. Since the search for new types of ring transformations of heterocycles on treatment with Cnucleophiles remains a topical problem (see, for example, a review devoted to ring transformations of pyrimidines 5 ) and the interest of synthetic chemists in the development of original synthetic procedures based on these reactions persists, it appears pertinent to follow the development and the characteristic features of studies carried out along this line.Carbanions are species presenting considerable interest, first of all, due to the fact that they have diverse structures and functional groups and thus they are potentially capable of being incorporated according to various patterns into molecules formed in the ring transformations of the pyridine ring.Carbanions are mild nucleophiles; therefore, they mainly add to a pyridine ring at position 4 rather than 2. 6-9 The resulting 1,4-dihydropyridines cannot undergo electrocyclic cleavage of the pyridine ring because it is possibleonly for 1,2-dihydropyridine derivatives. Apparently, this fact hampers the conduction of ring transformations of pyridine derivatives induced by C-nucleophiles. This is partly responsible for the fact that only few types of reactions involving carbanions can be found in the literature and are considered below. However, the great synthetic potential of ring transformations of the pyridine ring involving C-nucleophiles makes further efforts along this line not merely justified but even highly promising. II. CYCLOPENTADIENE DERIVATIVESThe first example of ring transformation of pyridinium salts on treatment with С-nucleophiles was represented by the Ziegler-Hafner synthesis 10,11 of azulenes; one variant of this reaction makes use of pyridin...

A Novel Ring Transformation of Pyridinium Salts as a Route to 4-Arylpyridines

“…Subsequently, a large number of reactions with ring opening and ring transformation of pyridine derivatives induced by nucleophilic reagents have been discovered and studied. [2,4,5] In particular, a number of new rearrangements, some of which are general for the chemistry of heterocyclic compounds, such as the amidine rearrangement [6,7] and the enamine rearrangement [2,8] of pyridine derivatives, and the unusual ring transformation of nitropyridinium salts into indoles [9] have been described in our previous publications. The main structural factors and conditions influencing the ring transformation pathway that have been identified to date provide grounds to expect great prospects for further research along these lines.…”

Reactivity of 4-Methylpyridinium Salts in a New Reaction of Ring Transformation of Pyridine and Isoquinoline Derivatives

“…Quite a number of the pyridine ring transformations under the action of nucleophiles was discovered lately [3,4]. First of all a series of new rearrangements should be mentioned, like amidine rearrangement [5,6], enamine rearrangement of pyridine derivatives [3,7], and the unusual reaction we discovered of the ring transformation of nitropyridinium salts into indoles [8,9].…”

“…Isoquinoline derivatives may be regarded both as a fused azine system which is characterized as a whole by a higher electron-deficiency with respect to nucleo philes [1,9], and as pyridine derivatives that typically enter into the nucleophilic additions and ring transformation reactions [1013].…”

Synthesis of tricyclic systems on the basis of σ-adduct of 3,5-dinitropyridin-2-ol with acetone

“…It is known that reactions of dinitropyridines with ketones in the presence of bases can be accompanied by rearrangements involving opening of the pyridine ring [4]. For example, 1-methyl-3,5-dinitropyridin-2(1H)-one reacts with acetone in the presence of organic bases to give p-nitrophenols [5] and p-nitroanilines [6].…”

“…We briefly reported in [7] that successive nucleophilic addition of acetone dicarbanion to 3,5-dinitropyridin-2-ol and double Mannich condensation yield tricyclic compounds containing a 3,7-diazabicyclo[3.3.1]nonane fragment. In continuation of these studies, in this work we examined in detail the product structure by two-dimensional high-resolution NMR techniques and X-ray analysis and synthesized a series of new 6-substituted 4,8-dinitro-2,6-diazatricyclo-[6.4.0.0 4,9 ]dodecane-3,11-diones from various primary amines. Initial 3,5-dinitropyridin-2-ol (1) was prepared according to the procedure described in [8] by nitration of pyridin-2-ol.…”