In this dissertation the chemical properties, as well as the physicochemical and spectral characteristics of N-substituted p-quinoneimines with substituents in the both ortho-positions towards to the imine carbon atom have been studied. These quinoneimines have a few features due to the presence of activated sterically strained C=N bond (ASSB). The increase in the C=N–X valence angle up to 130 degrees and above activates sterically strained C=N bond. The nucleophilic addition reactions preferably proceed under 1,2-addition scheme with formation of quinolide structure.
The novelty of this work is detection of unusual direction in reactions of N-substituted p-quinoneimines with two substituents in the ortho-positions towards to the imine carbon atom.
Characteristic features of the activated sterically strained C=N bond in N-substituted p-quinoneimines have been detected, that makes it possible to predict it. With help of precision atomic-molecular models of “Tartu Models” the activated sterically strained C=N bond is shown to appear in N-substituted p-quinoneimines with substituents in the both ortho-positions towards to the imine carbon atom when the C=N–X valence angle is equal 130 degrees and above. ASSB C=N is observed up to 145 degrees of the C=N–X valence angle. Quinoneimines with higher C=N–X valence angle are thermodynamically unstable and cannot be obtained.
As result of study of halogenation of some N-substituted p-quinoneimines and quantum-chemical calculations, it is established the orientation of enter of a halogen atom into quinoid ring in hydrohalogenation of N-substituted p-quinonimines can be determined by the LUMO density on the Carbone atom in quinoid ring.
It has been established there are a several process in the halogenation of N-arylsulfonyl-1,4-benzoquinimines, namely: the addition of a halogen molecule to C=C bond in quinoid ring with formation of cyclohexene structures; the dehydrohalogenation of cyclohexene structures with reduction of the quinonimine structure; the addition of hydrohalogen molecule formed in dehydrohalogenation of cyclohexene structures; prototropic rearrangement of cyclohexene structures with the reduction of a benzoic ring.
The thermodynamically unstable quinone imines have a valence C=N–X angle of 145o and more. They are found to form in bromination of N-substituted 1,4-benzoquinonimines and their reduced forms with the entry of two large bromine atoms into ortho-positions toward the imine carbon atom.
In the halogenation of N-substituted p-quinonimines the process of dehydrohalogenation are proven to play a significant role.
Cyclohexene polyhaloid (half-quinoid) compounds obtained in the halogenation of N-arylsulfonyl-1,4-benzoquinone imines are characterized by reduction and dehydrohalogenation reactions, reactions with N-containing heterocycles, tosylhydrazine, arysulfinic and hydrogen nitrid acid. The regiospecificity of the dehydrohalogenation reaction of half-quinoid compounds was established. The cyclohexene polyhaloid (half-quinoid) compounds are found to have the optical activity. The spontaneous separation of the enantiomers is observed and as a result the optical isomers were obtained.
The presence of activated sterically strained C=N bond in N-substituted p-quinone mono- and diimines has been predicted using precision atomic molecular models of “Tartu Models” by the value of the C=N–X valence angle.
Structural features of N-substituted p-quinone imines with ASSB C=N were determined by the results of X-ray diffraction analysis, as well as the features of their 1H and 13C NMR spectra.
The influence of the presence of ASSB C=N in N-substituted p-benzoquinone monoimines on the process of Z,E-isomerization has been established.
It is established the interaction of N-substituted p-quinone imines with ASSB C=N with alcohols occurs according under 1,2-addition scheme with the formation of compounds having quinolide structure.
It was found that ASSB C=N influences on the direction in reactions of N-arylsulfonyl-p-quinone imines with aromatic amines, hydrazines, nitric acid, dialkylphosphites, phosphinites. Despite steric C=N bonding difficulties, nucleophilic addition reactions occur predominantly under 1,2-addition or 1,2-addition-elimination scheme.
It is established the presence of ASSB C=N influences on the redox potentials of N-substituted p-quinone imines.
The characteristic features of the behavior of N-arylsulfonyl-p-quinonemono- and diimines in the conditions of mass spectrometric studies, where there are the processes of mono- and diprotonation of molecular ions, are determined.
Quantum-chemical calculations have determined the general regularities in the appearance of ASSB C=N in N-substituted p-quinone imines.
