Lactam and amide acetals. 52. Reaction of dimethylformamide diethylacetal with 2,2-dimethyl-4,6-dioxo-1,3-dioxane (Meldrum's acid)

Depending on the conditions of carrying out the reaction of dimethylformamide diethylacetal with the Meldrum's acid, either 2,2-dimethyl-4,6-dioxo-5-(N,N-dimethyl-aminomethylene)-1,3-dioxane or N,N,N¹N¹-tetramethylformamidinium salt of 2,2-dimethyl-4,6-dioxo-5-(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-yl)methylene-1,3-di-oxane are formed. The two compounds can react with primary amines to form N-substituted 2,2-dimethyl-4.,6-dioxo-5-aminomethylene-1,3-dioxanes.For Communication 51, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 184–187, February, 1988.     

Photochemical reactions of 1-methyl-4,6-diaryl-2(1H)-pyrimidinones in the presence of thiols

Photochemical reactions of 1-methyl-4,6-diaryl-2(1H)pyrimidinones 1a-b in the presence of thiols 2 are described. Irradiation of 1-methyl-4,6-diaryl-2(1H)-pyrimidinones 1a-b in benzene in the presence of thiols 2 gave the unexpected 2:1-adducts, 3-methyl-4,6-diaryl-5-aralkylthio-6-(1′-methyl-4′,6′-diaryldihydro-pyrimidin-2-on)yl-1,3-diazabicyclo[2.2.0]hexan-2-ones 3-6, of 1 and 2, whereas irradiation of 1a-b alone in benzene resulted in recovery of the unchanged 1a-b.     

Conformational analysis—XXVIII : Four-component equilibria in 1,3-dioxanes. Ring deformations and the chair-twist free energy difference

Four-component equilibria in substituted 1,3-dioxanes were applied to the determination of conformational energies not accessible by conventional equilibration, with the following conclusions: 1. The difference in free energy between the chair and twist forms of 2,2,trans - 4,6 - tetramethyl - 1,3 -dioxane is 7·4 kcal/mol. 2. Equatorial Me substituents at C-4,6 exert a palpable buttressing effect on the corresponding axial substituents. 3. Equatorial substituents at C-2 exert a similar buttressing effect on the geminal axial substituent. 4. The effect of equatorial t-Bu substitution or gem-dimethyl substitution at C-5 on conformational energy seems to be of minor importance. The more complex effects of equatorial 4-t-Bu substitution are discussed.     

Boat conformation in 2,5-substituted 1,3-dioxanes

The calculation of the energy equilibrium according to Pitzer between the chair and boat conformations in 2,5-substituted 1,3-dioxanes is presented, as well as the energies of the electrostatic dipole interactions. It is shown that the unsymmetrical boat conformation is stabilized in 2,5-dialkyl- and in 2,2-dimethyl-5-alkyl-5--alkoxyalkyl-1,3-dioxanes because of the presence of hetero atoms in the ring, because of the introduction of substituents in the 2 and 5 positions, and because of the interaction between the hybridized, unshared electron pairs of the oxygen atom at the apex of the boat with the hydrogen atom of the CH₂ group.     

Investigation of reactions of the organozinc reagents prepared from zinc and dialkyl dibromomalonates with the derivatives of 2-arylmethyleneindan-1,3-dione and 5-arylmethylene-2,2-dimethyl-1,3-dioxane-4,6-dione

Organozinc compounds prepared from dialkyl dibromomalonates and zinc react with 2-arylmethyl-eneindan-4,6-diones, 5-arylmethylene-2,2-dimethyl-1,3-dioxane-4,6-diones, as well as with 2-[4-(1,3-dioxoindan-2-ylidenemethyl)phenyl]methyleneindan-1,3-dione and 5-[4-(2,2-dimethyl-4,6-dioxo-1,3-dioxane-2-ylidenemethyl)phenyl]methylene-2,2-dimethyl-1,3-dioxane-4,6-diones to form dialkyl 3-aryl-1′3′-dioxaspiro(cyclopropane-2,2′-indan)-1,1-dicarboxylates, dimethyl 3-aryl-6,6-dimethyl-5,7-dioxa-4,8-dioxaspiro[2,5]octan-2,2-dicarboxylates, dialkyl 2-{4-[3,3-bis (alkoxycarbonyl)-1′,3′-dioxaspiro(cyclopropane-2,2′-indan)-1-yl]phenyl}-1′,3′-dioxaspiro[cyclopropane-2,2′-indan]-1,1-dicarboxylates, and dialkyl 2-{4-[2,2-bis(alkoxycarbonyl)-6,6′-dimethyl-4,8-dioxo-5,7-dioxaspiro[2,5]oct-1-yl]phenyl}-6,6-dimethyl-4,8-dioxo-5,7-dioxaspiro[2,5]octan-1,1-dicarboxylate respectively.     

17O NMR spectra of equatorial and axial hydroxycyclohexanes and 5-hydroxy-1,3-dioxanes and their methyl ethers

¹⁷O chemical shifts of axial hydroxyl groups in cyclohexanols are upfield of those of corresponding equatorial groups, but in 5-hydroxy-1,3-dioxanes the opposite is observed: the axial OH resonates downfield of the equatorial OH. The situation is the same in the corresponding methyl ethers and is, thus, not a result of intramolecular hydrogen bonding in the axial 5-hydroxy-1,3-dioxane, but appears to parallel the effect on ¹³C and ¹⁹F shifts observed in corresponding equatorial and axial 5-methyl- and 5-fluoro-1,3-dioxanes, which has been attributed to an upfield shifting effect of the antiperiplanar γ-located heteroatoms. Surprisingly, the reciprocal effect is not seen in the ring ¹⁷O shifts of the 5-hydroxy-1,3-dioxanes. A δ compression shift is seen in the ¹⁷O spectrum of trans-3,3,5-trimethylcyclohexanol (syn-axial OH and CH₃), analogous to the effect earlier reported in ¹³C spectra. Conversion of four of the alcohols to methyl ethers produces a large upfield effect on the ¹⁷O shift, larger in the cyclohexanols than in the 1,3-dioxane-5-ols. Similar upfield shifts have been recorded in the literature; their extent depends on whether the alcohols are primary, secondary or tertiary.     

Study of Nitrogen- and Sulfur-Containing Heterocycles. 57. Synthesis and Conversion of 4′-Substituted 5-(5-Amino-6-Pyrimidylthio)-2,2-Dimethyl-4,6-Dioxo-1,3-Dioxanes

By reaction of 4-substituted 5-amino-6-mercaptopyrimidines with 5-bromo-2,2-dimethyl-4,6-dioxo-1,3-dioxane, we have obtained 4′-substituted 5-(5-amino-6-pyrimidylthio)-2,2-dimethyl-4,6-dioxo-1,3-dioxanes. We have studied diazotization of these compounds by isoamyl nitrite. In the case of 4′-methoxy- and 4′-dimethylamino-substituted derivatives, we have obtained derivatives of novel heterocyclic systems: pyrimido[5,4-e][1,3,4]thiadiazine and pyrimido[5,4-e][1,3,4]thiadiazine-7-spiro-5′-1,3-dioxane, and in the case of the 4′-isopropylamino-substituted derivative we obtained 4-isopropyl-7-(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)-1,2,3-triazolo[5,4-d]pyrimidin-7-ylidene.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 613–623, April, 2005.     

Group 3 Metal Initiators with an [OSSO]‐Type Bis(phenolate) Ligand for the Stereoselective Polymerization of Lactide Monomers

A series of 1,ω‐dithiaalkanediyl‐bridged bis(phenols) of the general type [OSSO]H₂ with variable steric properties and various bridges were prepared. The stoichiometric reaction of the bis(phenols) 1,3‐dithiapropanediyl‐2,2′‐bis(4,6‐di‐tert‐butylphenol), 1,3‐dithiapropanediyl‐2,2′‐bis[4,6‐di(2‐phenyl‐2‐propyl)phenol], rac‐2,3‐trans‐propanediyl‐1,4‐dithiabutanediyl‐2,2′‐bis[4,6‐di(2‐phenyl‐2‐propyl)phenol], rac‐2,3‐trans‐butanediyl‐1,4‐dithiabutane diyl‐2,2′‐bis[4,6‐di(2‐phenyl‐2‐propyl)phenol], rac‐2,3‐trans‐hexanediyl‐1,4‐dithiabutanediyl‐2,2′‐bis[4,6‐di(2‐phenyl‐2‐propyl)phenol], 1,3‐dithiapropanediyl‐2,2′‐bis[6‐(1‐methylcyclohexyl)‐4‐methylphenol] (C₁, R=1‐methylcyclohexyl), and 1,4‐dithiabutanediyl‐2,2′‐bis[6‐(1‐methylcyclohexyl)‐4‐methylphenol] with rare‐earth metal silylamido precursors [Ln{N(SiHMe₂)₂}₃(thf)_x] (Ln=Sc, x=1 or Ln=Y, x=2; thf=tetrahydrofuran) afforded the corresponding scandium and yttrium bis(phenolate) silylamido complexes [Ln(OSSO){N(SiHMe₂)₂}(thf)] in moderate to good yields. The monomeric nature of these complexes was shown by an X‐ray diffraction study of one of the yttrium complexes. The complexes efficiently initiated the ring‐opening polymerization of rac‐ and meso‐lactide to give heterotactic‐biased poly(rac‐lactides) and highly syndiotactic poly(meso‐lactides). Variation of the ligand backbone and the steric properties of the ortho substituents affected the level of tacticity in the polylactides.     

The Structure of New Host Molecules that form Channel Inclusion Compounds

1,3-Benzenediamine,N,N′-bis(4,6-dichloro-1,3,5-triazine-2-yl) and 1,3,5-Triazine,2,2′-[2-methyl-1,3-phenylenebis(oxy)] bis(4,6-dichloro) were synthesized as host molecules. The inclusion compound of 1,3-Benzenediamine,N,N′-bis(4,6-dichloro-1,3,5-triazine-2-yl) crystallizes in the monoclinic crystal system in space group C2/c. The host molecule occupies the space group 2-fold special position and packed in the crystal lattice in such a manner as to leave channels running along the c axis of a rectangular cross-section. It crystallizes with two molecules of acetone that are hydrogen bonded to the amino nitrogen atoms. Molecules of 1,3,5-Triazine,2,2′-[2-methyl-1,3-phenylene bis(oxy)]bis(4,6-dichloro) are packed in the crystal in such a manner as to leave channels of a trapezoid cross-section that are running along the a axis. Guest molecules such as metanol, ethanol, and ethyl acetate can be used to fill the channels. The crystal structures of two inclusion compounds are described.     

Search for dioxocarbenes in photochemical reactions of 5-diazo-4,6-dioxo-1,3-dioxanes, associated diazirines, and S-ylides

On direct photolysis of 2,2-dialkyl-5-diazo-4,6-dioxo-1,3-dioxanes in the presence of pyridine, methanol or dimethyl sulfide as carbene traps, the yield of ‘carbene’ products does not exceed 27-28%. At the same time photochemical transformations of the related 3,3-diacyldiazirines and dioxosulfonium ylides of this series, evidently, occur without generation of carbene intermediates.     

An Efficient One‐pot Synthesis of Novel Spiro Cyclic 2‐Oxindole Derivatives of Pyrimido[4,5‐b]Quinoline,Pyrido[2,3‐d:6,5‐d′]Dipyrimidine and Indeno[2′,1′:5,6]Pyrido [2,3‐d]Pyrimidine in Water

A novel and facile one‐pot synthesis of spiro cyclic 2‐oxindole derivatives of pyrimido[4,5‐b]quinoline‐4,6‐dione, pyrido[2,3‐d:6,5‐d′]dipyrimidine‐2,4,6‐trione, and indeno[2′,1′:5,6]pyrido [2,3‐d]pyrimidine employing 6‐aminothiouracil (or 6‐aminouracil), isatin, and cyclic 1,3‐diketone (e.g. 1,3‐indanedione, dimedone, or barbituric acid) has been developed.     

Polymeric mesoions, 3. Synthesis of polymeric mesoionic 1,3-diazinium-olates via polymer analogous modification of a polythiourea from m-phenylenediamine and p-phenylene diisothiocyanate

Mesoionic poly(1,1′-(1,3-phenylene)-3,3′-(1,4-phenylene)-bis(5-decyl-2-decylthio-4,6-dioxo-1,3-diazine)) ( 6 ) was prepared by cyclisation of the isothiourea component of poly(1,1′-(1,3-phenylene)-3,3′-(1,4-phenylene)-bis(2-decylisothiourea)) ( 4 ) with decylmalonic acid (5) by use of dicyclohexylcarbodiimide (DCC). Polymer 4 was obtained by polymer analogous alkylation of poly(1,1′-(1,3-phenylene)-3,3′-(1,4-phenylene)-bisthiourea) ( 3 ). For comparison of spectroscopic data, 5-butyl-2-propylthio-4,6-dioxo-1,3-diphenyl-1,3-diazine ( 9 ) was synthesized as low molecular weight model compound.     

Reaction of 5-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide with electrophilic reagents: Bromine and nitric acid

Reactions of 5-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide with bromine and nitric acid lead to the electrophilic substitution of the hydrogen atom in the meta-position with respect to the nitro group. At thebromination the primarily formed 4-bromo-6-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide when kept in the solution loses an oxygen atom forming 4-bromo-6-nitrospiro[benzimidazole-2,1′-cyclohexane] 1-oxide and an isomerization product, 8-bromo-6-nitrospiro[3H-[2,1,4]benzoxadiazine-3,1′-cyclohexane] 4-oxide. The latter exposed to light turns into 4-bromo-6-nitrospiro[benzimidazole-2,1′-cyclohexane] 1,3-dioxide. The reaction of the initial 1,3-dioxide with nitric acid afforded 4,6-dinitrospiro[benzimidazole-2,1′-cyclohexan]-7-ol 1-oxide whose heating in o-dichlorobenzene resulted in 3,5-dinitro-1,8-diazatricyclo[7.5.0.0^2,7] tetradeca-2(7),3,5,8-tetraen-6-ol.     

Investigation in the Area of Furan Acetal Compounds. 13. Synthesis and Structure of 1,3-Dioxacyclanes Based on Furfural and Glycerol

The optimum conditions were found for the condensation of glycerol with furfural. It was shown that the reaction of glycerol with furfural gives a mixture of the cis and trans isomers of five- and six-membered furan 1,3-dioxacyclanes. The cis- and trans-5-hydroxy-2-furyl-1,3-dioxanes were isolated by column chromatography, and their stereochemical structure was established by IR and NMR spectroscopy.     

Synthesis and three-dimensional structure of 5,5-disubstituted 2-alkoxy-1,3-dioxanes

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.     

Vibrational and electronic spectral studies of substituted 1,3-dihydro-1,3-diphenyl-2-thioxo-2H,5H-pyrimidine-4,6-diones

The vibrational spectra of 1,3-diphenyl-; 1,3-di (4′-chlorophenyl)-; 1,3-di(3′-methoxyphenyl)-1,3-dihydro-2-thioxo-2H,5H-pyrimidine-4,6-diones in solid state (KBr pellet) and in solution (CHCl₃ and CCl₄) have been studied and assignments made. Tautomeric and hydrogen bonding behaviour are discussed. Electronic spectra in various solvents at different pH values are recorded. The effect of substituents, change of solvent on the π—π* and n—π* transitions of all the compounds is explained. The bathochromic and hypsochromic shifts observed when the neutral form changes to the cationic or anionic form depending on the pH of solution, are also discussed.     

NMR experiments on acetals—XXV: Conformational energy for the chair-twist interconversion of the 1,3-dioxane system

Trans-4-t-Bu-6-R-1,3-dioxanes (R = Me, Prⁱ and cyclohexyl) show temperature-dependent values for ²J(H—2) and ³J(H—4(6), H—5) in their PMR spectra. This is the result of the presence of twist-boat conformations. With the aid of typical limit-values of ²J(H—2) for the chair and twist forms, the amount of flexible conformations were determined as a function of temperature (Table 2), allowing the determination of the enthalpy change for chair-twist interconversion in 1,3-dioxane itself (6·2 ± 0·3 kcal/mole). Typical values for ²J(H—2) were obtained from a study of low temperature spectra and from appropriate model compounds of which 4-(1′-adamantyl)-6-t-Bu-1,3-dioxane served as the model for a genuine twist form with a twofold axis through C-2/C-5.     

Steerochemistry of heterocycles.

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.     

Synthesis and Characterization of O-Nitrosubstituted Polyimides

Poly(o-nitro)imides have been synthesized by one-stage polycondensation in DMAc at 130°C of 1,3-dichloro-4,6-dinitrobenzene with the di-potassium salt of pyromellitic or 3,3′,4,4′-benzophenonetetracarboxylic acid diimide. The structure was confirmed by elemental analysis, IR, and UV-Vis spectroscopy, and the influence of the o-nitrosubstituents on the solubility and the thermal stability of the prepared polymers was studied. These polymers could be used as pyrrone precursors. The model compound for these polymers has been also prepared by condensation of 1,3-dichloro-4,6-dinitrobenzene with potassium phthalimide.     

77Se NMR study of some organic selenium compounds formed in the selenium dioxide oxidation of ketones

⁷⁷Se NMR chemical shifts and ¹J(SeC) coupling constants were measured for nine organic selenium compounds: 4,5,6,7-tetrahydro-,4′,4′,6,6-tetramethylspiro[1,3-benzoxaselenole-2,1′-cyclohexane]-2′,4,6′-trione and closely related derivatives, bis(2-hydroxy-4,4,6,6-tetramethyl-3-oxo-1-cyclohexenyl) selenide and derivatives, and 1,5,5-trimethyl-7-selenabicyclo[2.2.1]heptane-2,3-dione. The chemicalshifts ranged from ?107 to 595 ppm from the external dimethyl selenide standard. The bridged selenabicyclic compound showed a small coupling constant (42 Hz).