Aziridinyl ketones and their cyclic anils. 9. Substituted 1,3-diazabicyclo[3.1.0]hex-3-enes

Aryl-substituted 1,3-diazabicyclo[3.1.0]hex-3-enes were obtained by the reaction of ,-dibromodihydrochalcones with ammonia and formaldehyde (or acetone). Their structures were confirmed by spectral methods and x-ray diffraction analysis.See [1] for Communication 8.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1064–1070, August, 1989.     

Copper-catalyzed cascade approach to 1,3-diazabicyclo[3.1.0]hex-3-enes from aziridines and ethyl diazoacetate

An efficient and general synthesis of 1,3-diazabicyclo[3.1.0]hex-3-enes via the copper-catalyzed cascade reaction of aziridines with ethyl diazoacetate is described.     

Aziridinyl ketones and their cyclic anils. 11. Fluorine-containing photochromes

Chalcones with fluorine-containing groups were converted to ,-dibromides and then to cyclic aziridinyl anils. The introduction of an electron-acceptor trifluoromethylsulfonyl group leads to a significant, although smaller as compared with the nitro group, bathochromic shift of the minimum of the reflection spectrum. Fluorine-containing substituents decrease appreciably the dark-decolorization time of the aziridinyl anils.See [1] for Communication 10.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1179–1184, September, 1991.     

Aziridinyl ketones and their cyclic anils. 6. Proton-acceptor capacities of aziridinyl ketones

The proton-acceptor capacities of a number of cis- and trans-aziridinyl ketones were estimated by IR spectrometry from the shifts of the OH bands of phenol, p-bromophenol, and trichloroacetic acid.It is shown that the cis isomers interact with all of the proton donors, whereas the trans isomers interact only in CCl₃COOH.The latter is due to the fact that a strong intramolecular hydrogen bond exists in the trans-NH-aziridinyl ketones, whereas considerable steric hindrance to complexing develops in the trans-N-alkylaziridinyl ketones.It was established that the formation of complexes takes place at the carbonyl group of the aziridinyl ketones.See [1] for Communication 5.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1641–1644, December, 1981.     

Aziridinyl ketones and their cyclic anils. 7. Solvolysis of 1,2-diaryl-1,1a-dihydroazirino[1,2-a]-quinoxalines

Refluxing of 1,2-diaryl-1,1a-dihydroazirino[1,2-a]quinoxaline in 1-propanol leads to 3-aryl-1-arylmethyl-2-propoxy-1,2-dihydroquinoxalines or to aryl(3-aryl-1-arylmethyl-1,2-dihydroquinoxalin-2-yl) (3-aryl-2-hydroxy-1,2-dihydroquinoxalin-1-yl)methanes. Both processes are due to opening of the C-C bond of the aziridine ring; however, in the first process the ylids formed react with solvent molecules, whereas in the second process dimerization of the ylids with the participation of the water present in the solvent is observed.See [1] for communication 6.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 673–679, May, 1984.     

NMR structural elucidation and photochromic behavior of new 1,3-diazabicyclo[3.1.0]hex-3-ene derivatives

Several 6-(4-nitrophenyl)-4-phenyl-1,3-diazabicyclo[3.1.0]hex-3-ene derivatives having various substituents on C² were synthesized, and their ¹H NMR spectra and photochromic behavior were examined.     

Aziridinyl ketones and their cyclic anils. 8. 1,2-Diaryl-1,1a-dihydroazirino[1,2-a]quinoxalines from substitute o-phenylenediamines and chalcone dibromides

The reaction of 4-R-substituted (R=Br, Cl, OC₂H₅, CN, NO₂) 1,2-phenylenediamines with 1,3-diaryl-2,3-dibromo-1-propanones in the presence of triethylamine gave 1,2-diaryl-5-R-1,1a-dihydroazirino[1,2-a]quinoxalines, which undergo isomerization in an acidic medium to give 2-aryl-3-arylmethylene-7-R-quinoxalines. The dipole moments were measured, and the polarities of the synthesized compounds are discussed.See [1] for communication 7.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 24, No. 3, pp. 328–333, March, 1988.     

Synthesis and exploring the excited-state PES of photochromic hydrogen bond-assembled [2]rotaxane based on 1,3-Diazabicyclo-[3.1.0]hex-3-enes

Here, the synthesis of photochromic hydrogen bond-assembled [2]rotaxanes using bis-fumarate as a thread for the first time is reported. In fact, photochromic 1,3-diazabicyclo[3.1.0]hex-3-ene moieties were used as stoppers and two-atom spacers managed good binding sites for the tetralactam macrocycles in clipping reactions. Moreover, the yields of photochromic [2]rotaxanes highly depended on the NO₂ substituent stoppers. While the thread with a para –NO₂ substituent as stopper units was shown to be an excellent template for the synthesis of photochromic [2]rotaxanes. The structures of the [2]rotaxanes are established clearly in solution by chemical shifts of the ¹H ¹³C NMR signals and UV–Vis spectra. A pronounced bathochromic shift was occurred in the excitation wavelength of photochoromic [2]rotaxanes compared with the absorption band of photochromic threads. Therefore, these organizations can be applied in light-driven molecular switches and motors. The reversible transformation of trans and cis geometric photoisomers under UV radiation was identified. In other efforts, the possibility of the process of trans to cis interconversion of the fumarate linker under UV irradiation has been examined computationally and it has appeared that it may cause the transverse of the bis-fumarate linker inside the tetralactam macrocycle to some extent.

     

Generation and reactivity of sterically hindered bicyclo[3.1.0]hex-1-enes

2-t-butylbicyclo[3.1.0]hex-1-ene dimerizes primarily by a [σ+ π] way, whereas 2,5-di-t-butylbicyclo[3.1.0]hex-1-ene undergoes an unusual hydrogen shift reaction to 1,3-di-t-butyl-2-methylcyclopentadiene.     

Conformational analysis of 2-phenyl-1,3-diazabicyclo[3.1.0]hexane

The 2-phenyl-1,3-diazabicyclo[3.1.0]hexane molecule was subjected to conformational analysis within the framework of the Westheimer method. The optimum conformations of two of its possible stereoisomers (endo and exo) were found, and the equilibrium concentrations of the latter were calculated and found to be 62 and 38%, respectively. The results of the calculations are in good agreement with the PMR spectroscopic data.     

Photochemistry of azole N-oxides. Facile photoisomerisation of 2H-imidazole N-oxides to 1,3-diaza-6-oxabicyclo[3.1.0]hex-3-enes and synthesis of a 1,3-diaza-4,7-dioxatricyclo[4.1.0.1,603,5]heptane

Ultraviolet irradiation of a series of 2H-imidazole N-oxides 2 has been shown to effect a clean isomerisation to derivatives of the new ring system, 1,3-diaza-6-oxabicyclo[3.1.0]hex-3-ene, 7 . Epoxidation of a representative 7 has given access to the hitherto inaccessible trans-fused 1,3-diaza-4,7-dioxatricyclo[4.1.0. ^1,60^3,5]-heptane ring system 9 .     

Azirino[c]imidazolyl ylides in the domino reaction of 2,2-dialkyl-4,6-diaryl-1,3-diazabicyclo[3.1.0]hex-3-enes with dichlorocarbenes. Synthesis of (1RS,5SR, 6RS)-4-(alk-1-enyl)-1,5-diaryl-3,7,7-trichloro-2,4-diazabicyclo[4.1.0]hept-2-enes

The reaction of 2,2-dialkyl-4,6-diaryl-1,3-diazabicyclo[3.1.0]hex-3-enes with dichlorocarbene to give (1RS,5SR,6RS)-4-(alk-1-enyl)-1,5-diaryl-3,7,7-trichloro-2,4-diazabicyclo[4.1.0]hept-2-enes has been studied. Quantum-chemical calculations using the DFT B3LYP/6-31G(d) method have confirmed that the mechanism of the reaction includes the formation of azirino[c]imidazolium ylides and coordinated opening of the imidazole and aziridine rings with subsequent cyclization and dichloropropane formation. Dedicated to the respected memory of A. A. Potekhin __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 730–740, May, 2008.     

Photochemically induced [4+2]- versus [3+2]-cycloreversion reaction of hexasubstituted 2,3-diaza-bicyclo[3.1.0]hex-2-enes

Hexasubstituted 2,3-diaza-bicyclo[3.1.0]hex-2-enes containing large substituents at C-4 and C-6 upon irradiation undergo a novel [4+2]cycloreversion reaction leading to 2,3-diazahexatriens besides the normal [3+2]cycloreversion.     

Activation parameters for three reactions interconverting isomeric 4- and 6-deuteriobicyclo[3.1.0]hex-2-enes.

Classic investigations of thermal equilibrations between 4,4-d2- and 6,6-d2-bicyclo[3.1.0]hex-2-enes (Doering, W. von E.; Roth, W. R. Angew. Chem., Int. Ed. Engl. 1963, 2, 115-122) and among deuterium-labeled and non-racemic 2-methyl-5-isopropylbicyclo[3.1.0]hex-2-enes (Delta3-thujenes) (Doering, W. von E.; Lambert, J. B. Tetrahedron 1963, 19, 1989-1994 and Doering, W. von E.; Schmidt, E. K. G. Tetrahedron 1971, 27, 2005-2030) and bicyclo[3.1.0]hex-2-enes (Cooke, R. S.; Andrews, U. H. J. Am. Chem. Soc. 1974, 96, 2974-2980) identified three different paths leading to distinct degenerate products. The equilibrations take place through [1,3]-carbon shifts with retention,suprafacial and inversion,antarafacial stereochemistry and a two-centered epimerization resulting in enantiomerization of the bicyclic skeleton through a "ring-flip" process. Activation parameters for the rate constants kr, kf, and ki associated with these paths have now been secured: Ea 43.8, 44.3, 44.8 kcal/mol and log A 14.1, 14.2, 14.1, respectively, nearly identical values, differing by less than probable error limits, consistent with a rate-determining formation followed by a rapid partitioning of a common diradical intermediate under dynamic control.     

Copper-mediated aerobic synthesis of 3-azabicyclo[3.1.0]hex-2-enes and 4-carbonylpyrroles from N-allyl/propargyl enamine carboxylates

Synthetic methods for 3-azabicyclo[3.1.0]hex-2-enes and 4-carbonylpyrroles have been developed that use copper-mediated/catalyzed reactions of N-allyl/propargyl enamine carboxylates under an O(2) atmosphere and involve intramolecular cyclopropanation and carbooxygenation, respectively. These methodologies take advantage of orthogonal modes of chemical reactivity of readily available N-allyl/propargyl enamine carboxylates; the complementary pathways can be accessed by slight modification of the reaction conditions.