Cyanoethylation of some n-substituted 2,5-dimethyl-4-piperidones

1,2,5-Trimetnyl- and 1-(-chlorocrotyl)-2,5-dimethyl-5-(-cyanoethyl)-4-piperidones were synthesized and separated into individual isomers. The corresponding isomeric 5-(-carboxyethyl)-4-piperidones were obtained by hydrolysis. The isomeric 1,2,5-trimethyl-3,5-bis(-cyanoethyl)- and 1,2,5-trimethyl-3,3,5-tris(-cyanoethyl)-4-piperidones were synthesized by subsequent cyanoethylation of the individual 1,2,5-trimethyl-5-(-cyanoethyl)-4-piperidone isomers.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 479–481, April, 1971.     

PMR studies of the deuteration and hydration of 4-piperidones

PMR spectra of substituted 4-piperidones in base and salt forms in D₂O, water and other solvents are reported, and spectral characteristics interpreted in terms of equilibria between free ketone and 4,4-dideuteroxy (or hydroxy) forms. It is shown that 1-mono and 1,3-disubstituted-4-piperidones exist extensively as the corresponding dideuteroxy (or hydrated) species in D₂O (or H₂O) provided the ring nitrogen atom is positively charged, and that 3-substituents decrease the population of these forms. The facile D/H exchange of α-protons in the piperidone bases is also demonstrated.     

Reaction ofβ,β -dimethyldivinyl ketone with 2,5-dimethyl- and 1,2,5-trimethyl-4-piperidones

1-(3-Oxo-5-methyl-4-hexen-1-yl)-2,5-dimethyl-4-piperidone, 5-(3-oxo-5-methyl-4-hexen-1-yl)-2, 5-dimethyl-4-piperidone, and 5-(3-oxo-5-methyl-4-hexen-1-yl)-1,2,5-trimethyl-4-piperidone were synthesized. In the absence of a catalyst,-dimethyldivinyl ketone adds to 2,5-dimethyl-4-piperidone at the 1-position, while in the presence of alkali it adds at the 5-position.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 350–351, March, 1971.     

Catalytic enantioselective conjugate addition of dialkylzinc reagents to N-substituted-2,3-dehydro-4-piperidones

The first, highly enantioselective, copper/phosphoramidite-catalyzed conjugate addition of dialkylzinc reagents to N-substituted 2,3-dehydro-4-piperidones is described.     

Mass spectroscopic study of 2,5-dimethyl-4-benzoyl- and 2,5-dimethyl-4-benzylpyridine derivatives

The dissociative ionization of sixteen 4-benzoyl- and 4-benzylpyridine derivatives and their deuteroanalogs has been studied. An ortho effect, due to the benzoyl and benzyl radicals in the methyl group in the 5-position of the pyridine ring, has been detected. It has also been established that fragmentation of 4-benzoylpyridines substituted with a nitro group in the benzene ring leads to [M-OH]⁺ ions, due to the ortho effect, whereas fragmentation of 4-benzylpyridines leads to [M-C₆H₅R]⁺ ions. The probability of a given process depends on the position and nature of any substituent in the benzene ring; this makes it possible to identify different isomers in a given series of compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 810–816, June, 1987.     

Arylation of 2,5-dimethyl-4-phenylpyridine

The position of the pyridine ring is arylated by reaction of 2,5-dimethyl-4-phenylpyridine with phenyllithium and p-tolyllithium. Destructive oxidation of the diaryl-substituted pyridines primarily affects the pyridine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1359–1361, October, 1970.     

Copper-catalyzed asymmetric 1,4-addition of alkenyl alanes to N-substituted-2-3-dehydro-4-piperidones

Readily available vinyl alanes are used in the Cu-catalyzed asymmetric conjugate addition reaction to N-substituted-2-3-dehydro-4-piperidones. The enhanced reactivity of recently developed and easily prepared phosphine amine ligands in combination with inexpensive Cu(II)naphtenate (CuNp) allows the introduction of a great variety of alkenyl, alkyl, and aryl aluminums in high enantioselectivity.     

Synthesis of 2,5-dimethyl- and 1,2,5-trimethyl-4-dimethoxyphosphinylpiperid-4-ols

Dimethyl phosphite is condensed with 2,5-dimethyl- and 1,2,5-trimethylpiperid-4-ones in the presence of alkali metal alkoxides. It is shown that 2,5-dimethyl- and 1,2,5-trimethyl-4-dimethoxyphosphinyl-piperid-4-ols are formed in both cases in the same stereoisomeric forms and in high yields. Methylation of the piperidol isomer which was not substituted at the nitrogen atom indicated that the two piperidols formed had the same configuration.     

2,5-Dimethyl-4-phenyl- and 3,6-dimethyl-2,4-diphenylpiperidines

2,5-Dimethyl-4-phenylpiperidine and 3,6-dimethyl-2,4-diphenylpiperidine were obtained by reduction of the corresponding substituted pyridines. Several of their transformations are examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1356–1358, October, 1970.     

Stereochemistry of nitrogen heterocycles. 68. Stereochemistry of 2,5-dimethyl-4-piperidone, 2,5-dimethyl-4-piperidol,and their N-benzoyl derivatives

The isomers of 1-benzoyl-2,5-dimethyl-4-piperidone were obtained and equilibrated (89.8% cis 10.2% trans isomer, preferred conformations 2a, 5e, and 2a, 5a). The position of the equilibrium between the isomers of 2,5-dimethyl-4-piperidone was determined by two independent methods (89.5% trans 10.5% cis isomer). The differences in the free energies of the isomers, the conformational energy of the -CH₃ group, and the energy of syn-axial 1,3-interaction between the CH and the unshared electron pair were calculated; the decrease in the conformational energy of the -methyl group in the series of piperidine (1.6), 4-piperidone (1.47), and N-acyl-4-piperidone (1.28 kcal/mole) was explained by the successive weakening of the repulsive interaction between the -CH₃ group and the n-pair of the nitrogen as a result of the flattening of the ring and of the conjugation between the free electron pair of the nitrogen and the electrons of the acyl carbonyl group. The last previously unknown fourth isomer of 2,5-dimethyl-4-piperidol, which exists in the 2e,4a,5a conformation, was obtained by the reduction of cis-1-benzoyl-2,5-dimethyl-4-piperidone followed by debenzoylation. In contrast to the secondary amine, its N-benzoyl- and N-benzyl-substituted derivatives exist in the alternative 2a,4e,5e conformation. The configurations and conformations of the isomers were determined by means of the IR and NMR spectra.For Communication 67, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 953–961, July, 1989.     

Diastereoisomeric 1,2,5-trimethyl-4-mtolylpiperidin-4-ols and 2,5-dimethyl-4-m-tolylpyridine

The preparation of 1,2,5-trimethyl-4-m-tolypiperidin-4-ol and the isolation of three of its diastereoisomers are described. The passage from this piperidinol to 2,5-dimethyl-4-m-tolylpyridine has been effected. Some derivatives of the latter compound have been obtained.Translated from Khimiya Geterotsiklicheskikh Soedinii, Vol. 6, No. 6, pp. 782–786, June, 1970.     

Reductive N-alkylation of 2,5-dimethyl-4-triphenylsilylpyridine over metal sulfides

Conclusions The Re₂S₇ catalyst was proposed, and optimum conditions were established, for the selective hydrogénation of the pyridine ring in 2,5-dimethyl-4-triphenylsilylpyridine and its subsequent N-ethylation with ethanol, without involving the phenyl radicals attached to silicon. The Pt and Pd sulfides are less active under analogous conditions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1901–1902, August, 1973.     

Benzylation of 2,5-dimethyl-4-phenyl(p-alkylbenzyl) pyridines

New substituted 4-phenyl-2-benzyl- and 2,4-dibenzylpyridines were obtained, and some of their transformations were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 91–94, January, 1972.     

Mechanistic studies in the reaction of 4-phenyl-1,2,4-triazoline-3,5-dione with 2,5-dimethyl-2,4-hexadiene

Secondary isotope effect measurements of methanol adducts from the reaction of 4-phenyl-1,2,4-triazoline-3,5-dione with 2,5-dimethyl-2,4-hexadiene, support the formation of an aziridinium imide intermediate rather than an open dipolar intermediate in the rate determining step.     

Investigation of 2,5-disubstituted silylfurans by PMR spectroscopy

The¹H,¹³C, and²⁹Si NMR spectra of S-substituted furfurals and the corresponding diethyl acetals containing various alkylsilyl substituents at position S of the furan ring were studied in comparison with the carbon- and sulfur-containing analogs and also with a series of monosubstituted silylfurans. In cases where the substituent was conjugated with the residue of the furan molecule the effect of the substituent at position S of the furan was transmitted to C of the aldehyde group. The reverse effect was also observed. It was determined that the contribution from the aldehyde group and the substituents at position S of the furan to the screening of the carbon nuclei of the furan ring was not additive.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 449457, April, 1996.     

Synthesis of benzoates of 1,4-bis(2,5-dimethyl-4-hydroxypiperidino)-2-butene and 1,4-bis-(2,5-dimethyl-4-hydroxypiperidino)-2-butyne

1,4-Bis(2,5-dimethyl-4-hydroxypiperidino)-2-butene and 1,4-bis(2,5-dimethyl-4-hydroxypiperidino)-2-butyne (II and III) were obtained by the action of 1,4-dibromo-2-butene and 1,4-dibromo-2-butyne on the form of 2,5-dimethyl-4-piperidol (I). The benzoates (IV and V) were obtained by acylation of II and III with benzoyl chloride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 352–353, March, 1971.     

Synthesis of 4-substituted 1-methyl(benzyl)-2,5-dimethyl-4-R-aminopiperidines

Schiff base derivatives of 1-methyl(benzyl)-2,5-dimethylpiperidin-4-ones with phenyl, -pyridyl, benzyl, and -hydroxyethyl substituents attached to the imine nitrogen atom react with organometallic compounds to give analogously substituted piperidine bases with methyl, allyl, phenyl, and benzyl substituents in the 4-position. Pure individual geometric isomers of these newly synthesized compounds have been isolated and their structures determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 954–958, July, 1987.     

Synthesis and thermochemistry of 4-diazo-1,1-dimethyl-1-silacyclohexa-2,5-diene

A vastly improved synthesis of 1,1-dimethyl-1-silacyclohexa-2,5-diene-4-one is described. Direct conversion of the ketone to the diazo derivative is easily accomplished, but a simpler method, not involving the ketone, is presented for synthesis of the title compound. In an attempt to observe rearrangement of the diazo system, pyrolysis under a variety of techniques was performed. No evidence of formation of a silabenzene was obtained.