首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The fundamental possibility of the synthesis of 2-substituted 1,3-dioxanes by reaction of 1,3-dioxanium perchlorates with organometallic compounds is demonstrated. A method for the synthesis of acyl derivatives of heterocycles was developed on the basis of these compounds. The existence of 2,2,4,4-substituted 1,3-dioxanes in the twist conformation was shown by 1H NMR spectroscopy; the twist conformation is explained by the effect of nonbonded 1,3-syn-axial interactions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1172–1179, September, 1978.  相似文献   

2.
A number of 2-alkyl-4,4,5-trimethyl- and 2-alkyl-4,4,6,6-tetramethyl-1,3-dioxanium perchlorates were obtained by acylation of 1,3-diols in the presence of 70% perchloric acid. Acid-catalytic cleavage of the heteroring with subsequent cyclization to 2-alkyl-1,3-dioxanium perchlorates occur in the reaction of 2-aryl(alkyl)-substituted and 2-unsubstituted 1,3-dioxanes with carboxylic acid anhydrides and 70% HClO4. Hypothetical detachment of a hydride ion by means of the acceptor acylium cation does not occur under the investigated conditions. The structures of the synthesized perchlorates were studied by PMR spectroscopy and it was shown that 1,3-dioxanium cations at room temperature exist in a state of rapid conformational isomerization of the chair-chair form. The rate of interconversion of the 2,4,4-trimethyl-1,3-dioxanium cation decreases appreciably as the temperature is reduced to –90°. as evidenced by marked broadening of the lines of the protons of the gemdimethyl groupings.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 182–186, February, 1977.  相似文献   

3.
Reaction of 2,4,4,6-tetramethyl-1,3-dioxanium perchlorate with lotsich reagents led to the synthesis of new silylethynyl-substituted 2,4,4,6-tetramethyl-1,3-dioxanes. According to the data of1H and13C NMR and x-ray diffraction analysis, it was established that the 1,3-dioxane ring of the products obtained has the chair conformation.Kuban' State Technological University, Krasnodar 350072, Russia. Ufa State Oil Technical University, Ufa 450062, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 487–493, April, 1998.  相似文献   

4.
The stereochemical peculiarities of substituted 1,3-dioxanes and 1,3-dithianes are discussed. The high probability of the existence of flexible conformations in these series, the considerable energy preference of the 5-C-axial position in the chair conformation of 1,3-dioxanes and 1,3-dithianes, and the definite preference of the 2-C-axial position in the chair conformation of 1,3-dithianes as compared with the axial conformations of the cyclohexane type are noted. The PMR spectra of stereoisomeric 2,5-dimethyl-5-isopropyl-1,3-dioxanes, 2-methy-l5-isopropyl-1,3-dithianes, and 2,2,5-trimethyl-1,3-dithiane are described, and their configurations and preferred conformations are proved. The results of a study of the epimerization of stereoisomers of substituted 1,3-dioxanes and 1,3-dithianes are examined, and the conformational energies of individual substituents in the 5-position of these cyclic systems are calculated on the basis of this examination.See [48] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 582–592, May, 1971.  相似文献   

5.
By the condensation of substituted aldehydes of vanillin series with 1,3-propanediol in boiling benzene in the presence of sulfo cation exchanger FIBAN K-1 as catalyst functionally 2-R-substituted 1,3-dioxanes were synthesized.  相似文献   

6.
Comparative conformational analysis of 2,2-dimethyl- and 2,2,5-trimethyl-1,3-dioxanes as well as their 2-heteroanalogs with silicon and germanium atoms has been performed by means of computer simulation using HF/pVDZ, hybrid DFT PBE/3ξ, and RI-MP2/λ2 methods. The potential energy surface for all the studied compounds has revealed the presence of the chair and 2,5-twist conformers. The latter form, in the case of substituted 1,3-dioxa-2-silacyclohexanes at the HF/pVDZ level, is a transition state rather than an intermediate minimum. The molecules of 2-sila- and 2-germa-1,3-dioxacyclohexanes exhibit an enhanced conformational flexibility as compared to the 1,3-dioxanes.  相似文献   

7.
Syntheses, structures, spectral characteristics, and chemical properties of 1,3-dioxanium salts are reviewed.Kuban State Technological University, Krasnodar 350072, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 291–316, March, 1999.  相似文献   

8.
The presence of a 2′-tertiary hydrogen atom has a profound influence on the general fragmentation pattern of 4,6-dialkyl-1,3-dioxanes. Branching at the 2′-position induces a double hydrogen transfer reaction which is absent in the spectra of 4,6-n-alkyl-1,3-dioxanes.  相似文献   

9.
A 1,2-hydride shift in the phosphoric acid-promoted cyclodimerization of styrene oxide and its chloro derivatives under solvent-free conditions leading to 2,4-disubstituted 1,3-dioxolanes is described. Methoxy substituents on the aromatic ring of the styrene oxide prevent the 1,2-hydride shift reaction leading to substituted 1,4-dioxanes. A possible mechanism for the formation of the 1,3-dioxolanes is proposed.  相似文献   

10.
The conformational isomerization of 2-oxo-1,3-dioxane and its methyl analogs was investigated by means of ab initio RHF//6-31G(d,p) and MP2//6-31G(d,p) quantum-chemical methods. It is shown that in comparison with 1,3-dioxanes the potential energy surface of the mentioned compounds has a fewer number of stationary points and includes two minima corresponding to conformers of sofa or distorted sofa configuration and one maximum corresponding to 2,5-twist form. The value of potential barrier of interconversion of cyclic carbonates is significantly lower than that of the analogously substituted 1,3-dioxanes.  相似文献   

11.
2, 5-Disubstituted 1,4-dioxanes have been obtained by the oxidation of N-vinyllactams, represented by N-vinylpyrrolidone, N-vinylpiperidone, and N-vinylcaprolactam, and their structure has been shown by independent synthesis: the reaction of trans-2, 5-dichloro-1,4-dioxanes with alkali-metal salts of the lactams also gave 2,5-di(N-2-oxopolymethyleneimino)-1,4-dioxanes.  相似文献   

12.
2, 5-Disubstituted 1,4-dioxanes have been obtained by the oxidation of N-vinyllactams, represented by N-vinylpyrrolidone, N-vinylpiperidone, and N-vinylcaprolactam, and their structure has been shown by independent synthesis: the reaction of trans-2, 5-dichloro-1,4-dioxanes with alkali-metal salts of the lactams also gave 2,5-di(N-2-oxopolymethyleneimino)-1,4-dioxanes.  相似文献   

13.
The reaction of subsitituted 1,3-dioxanes with the diisobutyl ester of isobutylboric acid leads to the corresponding 1,3,2-dixaborinanes. The determining factor in the reactivity of the 1,3-dioxanes is the degree of substitution of the acetal atom.A. V. Bogatskii Physicochemical Institute, National Academy of Sciences of the Ukraine, Odessa 270080. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 160–162, February, 27, 1995. Original article submitted February 27, 1995.  相似文献   

14.
2,4,4,6,6-Substituted 1,3-dioxanium perchlorates were obtained by acylation of ditertiary 1,3-diols with carboxylic acid anhydrides in the presence of 70% perchloric acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 169–172, February, 1976.  相似文献   

15.
Russian Journal of Organic Chemistry - Condensations of chloromethyl propargyl(allyl) ethers with alkyl 3-oxobutanoates in the presence of pyridine gave substituted 1,3-dioxanes.  相似文献   

16.
trans-Stilbene oxide was oxidatively converted to 2-phenyl-1,3-dioxanes with phenyltrimethylammonium tribromide in the presence of various 1,3-diols and a catalytic amount of SbBr3 in DMSO at room temperature. Aromatic 1,2-diol, such as hydrobenzoin, was similarly converted to 2-aryl-1,3-dioxane derivatives under the same reaction conditions.  相似文献   

17.
Introduction of substituents in position 2 of 1,3-dioxanes decreases the torsional angles of the OCH2CH2CH2O moiety (4, 5, 5, 6) indicating an enhanced flattening in this part of the molecule. In geminally substituted 2-alkyl-2-phenyl-1,3-dioxanes the phenyl group isaxial, andgonal with respect to the rotameric state, while in ortho substituted derivatives, e.g. 2-methyl-2-(o-methylphenyl)-1,3-dioxane theaxial phenyl ligand assumes an intermediate rotameric position. Theaxial preference is not influenced by intramolecular dipole—dipole interaction generated by a p-substituent in the phenyl group as is shown for various 2-methyl-2-(p-substitutedphenyl)-1,3-dioxanes.

Mit 5 Abbildungen

Herrn Prof. Dr.K. Kratzl zum 60. Geburtstag gewidmet.

Auszugsweise vorgetragen bei der Tagung des Vereins Österreichischer Chemiker in Wien am 20. März 1975.  相似文献   

18.
The reaction of 4-phenyl- and 4,4-dimethyl-1,3-dioxanes with acetone cyanohydrin leads to hydrolytically unstable 2-(1-hydroxy-1-methylethyl)-5,6-dihydro-1,3-oxazines, which are readily saponified in alkaline medium to the corresponding 1,3-amino alcohols.  相似文献   

19.
Conclusions Acid-catalyzed cocondensation of formaldehyde and alkanals RCHO with styrene leads to 2-R-4-phenyl-1,3-dioxanes with equatorial orientation of substituent R in the 2-position, and with -methylstyrene to a mixture of 4-methyl-2-R-4-phenyl-1,3-dioxanes with axial and equatorial orientation of substituent R.The yield of the cocondensation products in this reaction reaches 60%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 899–902, April, 1982.  相似文献   

20.
It was established by PMR spectroscopy that a chair conformation with an axial orientation of the alkoxy substituent is the primary conformation for 5,5-disubstituted (and unsubstituted) 2-alkoxy-1,3-dioxanes. As compared with alkyl-1,3-dioxanes, 2-alkoxy-1,3-dioxanes are characterized by reversal of the chemical shifts of the axial and equatorial protons attached to C4, and C6.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1182–1185, September, 1981.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号