Dual reactivity of 1,2-disubstituted dihydro-N-heteroaromatic systems. 9. Alkaline hydrolysis and aromatization of N-actyl partially hydrogenated derivatives of pyrazine and quinoxaline

The aromatization with splitting of the N-actyl groups of 2,3-disubstituted N-acyl-and N,N-diacyl-1,2-dihydro-, and 1,2,3,4-tetrahydropyrazines and quinoxalines under the effect of alcohol alkali was studied. A new reaction of recyclization of 1,4-diacyl-1,2,3,4-tetrahydroquinoxaline was discovered.Cf. [1] for Communication 8.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1551–1556, November, 1985.     

Dual reactivity of 1,2-disubstituted dihydro-N-heteroaromatic systems. 6. Electrochemical oxidation of N-acyl derivatives of 2-phenyl-1,2-dihydroquinolines

In the electrochemical oxidation of 1-acyl-2-phenyl-1,2-dihydroquinolines, first the radical cations of the starting compounds form; these then lose a benzoyl radical and go over to the 2-arylquinoline cations.For Communication No. 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 801–805, June, 1985.     

Dual reactivity of 1,2-disubstituted dihydro-N-heteroaromatic systems

The effect of the nature of the electrophile and the heteroring on the direction of reactions involving the aromatization of -substituted N-acyl dihydro-N-heterocycles with perchlorates of various organic cations was studied. It is shown that hard and intermediate electrophilic agents (triphenylmethyl, triindolylmethyl, and acetylium perchlorates) split out the substituent from the dihydroheterocycles to give stable N-acyl salts of the corresponding bases. Soft acceptors (2,2,6,6-tetramethyl-1-oxopiperidinium perchlorate) split out a hydride ion in all cases to give -substituted N-acyl salts of the corresponding bases.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 946–950, July, 1979.     

Dual type of reactivity op 1,2-disubstituted dihydro-N-heteroaromatic systems. 11. Aromatization of N-sulfonyl-1,2-dihydroquinolines and isoquinolines containing an α-indolyl or pyrrolyl substituent

When N-sulfonyl-1,2-dihydroquinolines and isoquinolines, containing an indolyl or pyrrolyl substituent at the -position, react with trityl perchlorate, this substituent is split off, and N-sulfonyl quinolinium and isoquinolinium cations and tritylindole or tritylpyrrole are formed. A similar reaction with 2,2,6,6-tetramethyl-1-oxopiperidinium perchlorate proceeds with splitting of hydrogen or retention of the -substituent, which leads to the corresponding -substituted N-sulfonylquinolinium and isoquinolinium cations.For Part 10, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1516–1518, November, 1986.     

Dual reactivity in 1,2-disubstituted dihydro-N-heteroaromatic systems. 12. Aromatization of 1-substituted-2-(indol-3-yl)-1,2-dihydroquinolines with 1,3,5-trinitrobenzene

As the electron-acceptor properties of the N-substituents in 1-R-2-(indol-3-yl)-1,2-dihydroquinolines decrease, their ability to undergo heterolysis of the internuclear C-C bond to give ion pairs of 1-R-quinolinium cations and indole anions decreases. Reaction of these ion pairs with 1,3,5-trinitrobenzene gives salts of 1-R-quinolinium cations and the 1-(indol-3-yl)-2,4,6-trinitrocyclohexadiene anion. With undissociated dihydroquinolines, aromatization under similar conditions gives salts of 1-R-2(indol-3-yl)quinolinium cations and the 1,1-dihydro-2,4,6-trinitrocyclohexadiene anion.For Communication 11, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 80–84, January, 1988.     

Dual reactivity of 1,2-disubstituted dihydro-N-heteroaromatic systems. 4. Factors that affect the rate of aromatization of substituted N-acyldihydropyridines

The rate of dehydroaromatization of N-acyldihydropyridines under the influence of the 2,2,6,6-tetramethyl-1-oxopiperidinium cation increases in the case of electron-donor substituents and decreases in the case of electron-acceptor substituents in the acyl residue or in the () positions of the pyridine ring. The presence of an annelated benzene ring also decreases the rate of aromatization of dihydropyridines.See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 367–370, March, 1982.     

Dual reactivity of 1,2-disubstituted dihydro-N heteroaromatic systems. 7. Aromatization of 1-methyl-2-phenyl-1,2-dihydroquinoline by quinonimines

In the aromatization of 1-methyl-2-phenyl-1,2-dihydroquinoline with substituted quinonimines, 1-methyl-2-phenylquinolinium salts of anionic hydride -complexes form, when then rearrange to iminyl anions. For comparison under Yanovskii reactions conditions, hitherto unknown acetonyl -complexes of quinonimines were synthesized.For Communication 6, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 806–809, June, 1985.     

Dual reactivities of 1,2-disubstituted dihydro-N-heteroaromatic systems. 3. Electrochemical aromatization of substituted N-acyldihydropyridines and imidazoles

The principal pathway in the fragmentation of the cation radicals of N-acyl- ()-substituted 1,4-dihydropyridines and 1,2-dihydroisoquinolines, as well as 1,2-dihydroimidazoles and 1,2-dihydrobenzimidazoles, that are formed in the electrochemical oxidation of the indicated N-acyldihydro-N-heteroaromatic systems is the loss of a proton and the subsequent loss of another electron or detachment of an N-acyl residue in the form of a cation and subsequent detachment of an electron to give the corresponding ()-substituted heteroaromatic cations.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 361–366, March, 1982.     

Dual reactivity of 1,2-disubstituted dihydro-N-heteroaromatic systems. 2. Mechanism of the dehydrogenation of N-acyldihydroquinolines and isoquinolines with 2,2,6,6-tetramethyl-1-oxopiperidinium perchlorate

The mechanism of the heterolytic dehydrogenation of various N-acyl derivatives of -substituted 1,2-dihydroquinolines and isoquinolines with 2,2,6,6-tetramethyl-1-oxopiperidinium perchlorate was investigated.See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 78–84, January, 1981.     

Twofold reactivity of 1,2-disubstituted dihydro-n-heteroaromatic systems. 10. Synthesis and aromatization of ferrocene-containing hantzsch esters

1-Ferrocenylphenyl-4-aryl(furyl)-2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridines and 4-ferrocenyl-2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridines (Hantzsch esters) have been prepared, and their reactions with triphenylcarbenium and 1-oxo-2,2,6,6-tetramethyl-piperidinium perchlorate salts have been studied. Treatment with triphenylmethyl perchlorate results in oxidation of the ferrocenyl substituent to the ferrocenium cation, whereas treatment with the oxoammonium cation results in aromatization and the formation of salts containing a pyridinium cation and a neutral ferrocene ring. A 4-ferrocenyl-containing Hantzsch ester which was unsubstituted at the nitrogen atom constituted a single exception to this trend; it could be aromatized only upon treatment with sulfur.For Communication 9, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1094–1101, August, 1986.     

Synthesis and transformations of enantiomeric 1,2-disubstituted monoterpene derivatives

Regio- and stereospecific addition of chlorosulfonyl isocyanate to (+)- and (−)-α-pinene 1 resulted in enantiomerically pure β-lactams 2, which were converted to enantiomeric β-amino esters 3 and 1,3-amino alcohols 4 and 6 with ee >99%. The resulting 1,3-difunctional compounds 3, 4 and 6 were transformed to fused saturated 1,3-heterocycles such as tetrahydro-1,3-oxazines 7 and 9, 2,4-pyrimidinedione 11 and 2-thioxopyrimidin-4-one 13 enantiomers.     

The preparation of the benzo[4,5]cyclohepta[1,2-b]pyrazine and benzo[4,5]cyclohepta[1,2-b]quinoxaline systems

Benzo[4,5]cyclohepta[1,2-b]quinoxaIine 2 , benzo[4,5]cyclohepta[1,2-b]pyrazine 3a and benzo[4,5]cyclohepta[1,2-b]quinoxaline 4 were prepared from 4,5-benzotropolone and 1,2-phenylenediamine, ethylenediamine and 1,2-diaminocyclohexane, respectively. Compound 3a was methylated to 3b .     

Effect of spatial configuration on adhesion of 1,2-disubstituted cyclohexane derivatives

Spatial configuration has a significant effect on chemical self-assembly. However, the importance of spatial configuration in supramolecular adhesive materials has been frequently ignored. In this study, the effects of the spatial configuration on cohesion and adhesion were investigated. Owing to the diversities of the chemical structures and assembly patterns, 1,2-disubstituted cyclohexane derivatives were used in this combined experimental and theoretical investigation. The self-sorting assembly of enantiopure isomers improved cohesion but had a negative effect on adhesion. In contrast, racemic mixtures displayed stronger adhesion effects. Moreover, it was proven that the cis-configuration was more favorable for supramolecular adhesion than the trans-counterpart. In addition, the influence of the spatial configuration of 1,2-disubstituted cyclohexane derivatives could be effectively mitigated by hydrogen bond donors or acceptors. The addition of natural acids yielded three-dimensional polymeric networks, in which the spatial configuration was not the decisive factor for supramolecular adhesion.     

Titanium(III) chloride and electrochemical reduction of pyrazine,quinoxaline and triazine derivatives and of their salts

The reduction of pyrazine, quinoxaline and triazine derivatives by titanium(III) chloride leads to di- or tetrahydrogenated compounds. High yields of tetrahydro compounds are also obtained through the reduction of quinoxalinium salts. These results are compared with those obtained by electrochemical reduction.     

Synthesis of 3,20-disubstituted chlorophyll-a derivatives and reactivity of the substituents

Methyl 20-bromo-pyropheophorbide-a possessing a vinyl group at the 3-position and its analogs having 3-ethyl, 3-(1-hydroxyethyl) and 3-acetyl groups were prepared by modifying naturally occurring chlorophyll(Chl)-a. The 20-bromo-chlorins were cross-coupled with vinyl- and 1-ethoxyvinyl-tributyltins in the presence of a Pd(0) catalyst to afford 20-vinyl- and acetyl-chlorins, respectively. The interconversions among the above four C2-functional groups at the 3-position were readily performed in the semi-synthetic Chl derivatives, but no modification of the 20-vinyl and acetyl groups was observed. The difference of the chemical reactivity is ascribable to the steric factor: the 3¹-position was less sterically hindered than the 20¹-position. Single hydrogenation and hydration of 3,20-divinyl-chlorin and reduction of 3,20-diacetylchlorin proceeded exclusively at the 3-position. The redmost (Qy) bands in electronic absorption spectra of the semi-synthetic Chl derivatives in a diluted dichloromethane solution were controlled by the 3,20-substituents. The 3-substituent effect on their Qy maxima was determined by the electronic factor (their electronegativity), while the 20-substituent effect was primarily dependent on the steric factor (their local size).     

O-Methylephedrine: a versatile and highly efficient ortho-directing group. Synthesis of enantiopure 1,2-disubstituted ferrocene derivatives.

O-Methylephedrine was identified as a very efficient chiral auxiliary for ortho-lithiation reactions of ferrocenes. (1R,2S)-O-Methylephedrine [CH(3)NHCH(CH(3))CH(Ph)OCH(3)] was reacted with N-ferrocenylmethyl-N,N,N-trimethylammonium iodide [FcCH(2)N(CH(3))(3)I; Fc = ferrocenyl] to give (1R,2S)-N-ferrocenylmethyl-O-methylephedrine. Treatment of this compound with t-BuLi in pentane followed by quenching with the electrophiles iodine, dibromotetrafluoroethane, chlorodiphenylphosphine or benzophenone gave 2-substituted ferrocenes in 98% de and with the (R(p))-ferrocene configuration. Subsequently, the chiral auxiliary could be replaced by systems including dimethylamine, acetate, diaryl- or dialkylphosphines to give a number of enantiopure bifunctional 1,2-disubstituted ferrocene derivatives such as (R(p))-N-2-iodo- or (R(p))-N-2-bromoferrocenylmethyldimethylamine or (R(p))-2-acetoxymethyl-1-diphenylphosphinoferrocene. As an application, ferrocenyl diphosphines possessing a planar (R(p))-ferrocene configuration only [1,2-(PPh(2))FcCH(2)PR(2), R = Cy, Ph, [3,5-(CF(3))(2)Ph]] were synthesized in three steps from O-methylephedrine and N-ferrocenylmethyl-N,N,N-trimethylammonium iodide in up to 77% overall yield.