Synthesis,stereochemistry, and isomeric transformations of 4-aryl-5-aroyl-2-methylthio-2-imidazolines

The corresponding 4-aryl-5-aroyl-2-methylthio-2-imidazolines were obtained by the reaction of complexes of cis- and trans-3-aroylaziridines and boron trifluoride with methyl thiocyanate. It is shown on the basis of spectral data that the aziridine ring is opened regiospecifically at the C(₂) atom and stereospecifically with inversion of the configuration.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1484–1488, November, 1988.     

Synthesis and stereochemistry of 2,2,3-trimethyl-5-aryl-4-aroyloxazolidines

cis-2,2,3-Trimethyl-5-aryl-4-aroyloxazolidines were obtained by heating complex boron trifluoride salts of trans-1-methyl-2-aryl-3-aroylaziridines with acetone. The reaction of complex boron trifluoride salts of cis-1-methyl-2-aryl-3-aroyl-aziridines leads to substituted benzaldehydes and -N-methylaminoacetophenones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 38–42, January, 1981.     

Synthesis,stereochemistry, and isomeric transformations of cis- and trans-1,2-dimethyl-4-aryl-5-aroyl-2-imidazolines

The corresponding trans- and cis-1,2-dimethyl-4-aryl-5-aroyl-2-imidazolines were obtained from complexes of cis- and trans-1-methyl-2-aryl-3-aroylaziridines with BF₃ by heating with acetonitrile. The reaction proceeds with inversion of the configuration of the starting 3-aroylaziridines. In the presence of bases the complexes of cis-1,2-dimethyl-4-aryl-5-aroyl-2-imidazolines readily undergo isomerization to the corresponding trans analogs. The structures of the products were established on the basis of the IR, PMR, and mass spectra and the results of elementary analysis. The configurations of the compounds were determined by means of the Overhauser nuclear effect.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 952–957, July, 1981.     

Reaction of 1-alkyl-2-aryl-3-(2-methyl-2,3-epoxypropionyl)aziridines with boron trifluoride etherate in methanol

The reaction of boron trifluoride etherate in methanol with trans-1-methyl(ethyl)-or cis-1-cyclohexyl-2-aryl-3-(2-methyl-2,3-epoxypropionyl)aziridines leads to the formation of the corresponding boron fluoride complexes on the nitrogen atom of the aziridine ring. Reaction with trans-1-cyclohexyl-2-phenyl-3-(2-methyl-2,3-epoxypropionyl)aziridines occurs with stereospecific opening of the aziridine ring to give diastereomeric 2-methyl-5-methoxy-5-phenyl-4-cyclohexylamino-1,2-epoxypen-tan-3-ones, as well as products from the opening of the epoxide and aziridine rings — tetrahydrofuranones and tetrahydropyranones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 596–600, May, 1986.     

Reactions of acyloxiranes with aliphatic ketones

Acyloxiranes react with aliphatic ketones in the presence of boron trifluoride etherate to give the corresponding 4-acyl-1,3-dioxolanes. The corresponding 4,5s-dimethyl-4r-acetyl-1,3-dioxolanes are formed in this case from 2,3t-dimethyl-2r-acetyloxirane, whereas a mixture of cis- and trans-1,3-dioxolanes is formed from trans-2-acetyl-3-phenyloxirane and acetone. The reaction of acyloxiranes with unsymmetrical ketones gives a mixture of the cis- and trans-1,3-dioxolanes with respect to the substituents attached to C-2 relative to the acetyl group, whereas the isomer ratio in this case depends on the effective volumes of the substituents attached to C-2.     

Polymerization of coordinated monomers. XXII. Ab initio molecular orbital study on the binary radical complexes of 2-methoxycarbonyl propyl radical with boron trichloride and with boron trifluoride as a model of growing radical end

The geometrical and electronic structures of the binary radical complexes of 2-methoxycarbonyl propyl radical with boron trichloride and with boron trifluoride were determined by using an ab initio molecular orbital method. The 2-methoxycarbonyl propyl radical complex was a model of the growing radical end in the copolymerization of methyl methacrylate in the presence of boron halides. The most stable structure of the binary radical complex composed of 2-methoxycarbonyl propyl radical with boron trichloride was a twisted form in which the dihedral angle between the vinyl group and the ester group was 32°, while that of the binary radical complex composed of methyl methacrylate radical with boron trifluoride was a planar form as the free radical. The frontier orbital energy of 2-methoxycarbonyl propyl radical was lowered by 0.06 au by the coordination of boron trichloride, while that was lowered only by 0.02 au by the coordination of boron trifluoride. The polymerization mechanism was elucidated on the basis of these predictions. © 1993 John Wiley & Sons, Inc.     

Etude de la Basicite de Composes Organophosphores Typiques dans Leurs Complexes de Lewis Avec le Trifluorure de Bore

Various complexes of boron trifluoride and typical organo-phosphours compounds have been investigated using proton and fluorine resonance (at variable temperature) and boron and phosphorus resonance. In BF₃, boron resonance is insensitive to the complex strength, but fluorine resonance suggests the possibility of various types of complexes on the phosphorus group or, additionally on the heteroatoms (e.g. oxygen, nitrogen) of the molecule. These complexes are probably σ type. Proton chemical shifts in the organo-phosphorus compounds follow the same trends as in similar complexes of amines, esters etc.; these perturbations may be mainly due to magnetic anisotropy effects; proton-phosphorus couplings conversely follow changes in phosphorus electronegativity.     

Polymer-Supported Boron Trifluoride

Polystyrene, cross-linked with 7.8% of divinylbenzene, formed a stable complex in chloroform with boron trifluoride containing 0.11% of boron, while cross-linked polystyrene-4-vinylpyridine resins containing 2–2.5% of pyridine rings formed a stable complex with boron trifluoride, containing 1.04% of boron. Both complexes catalyze conversions of aromatic aldehydes, ketones, and acids with alcohols into corresponding acetals, cyclic ketals, and esters; diphenylmethanol converts into ether. The structure of the alcohol plays an important role, with conversions decreasing in the order 1-butanol, 2-butanol, tert-butanol. Both complexes are very stable and in most cases more reactive than the cross-linked polystyrene-A1C1₃ complex.     

A proton magnetic resonance study of complexes of pyridine, 2-methylpyridine 3-methylpyridine, 4-methylpyridine,and 2,6-dimethylpyridine with borane and boron trifluoride

A variable temperature, proton magnetic resonance study has been made of complexes of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, and 2,6-dimethylpyridine with borane and boron trifluoride. By lowering the temperature and slowing ligand exchange, separate resonance signals can be observed for bulk and complexed molecules of the base. A direct comparison of the complexing abilities of these ligands was made by studying them in pairs with borane or boron trifluoride. The complexing abilities, as estimated from the NMR data, decreased in the order: 4-MePy > 3-MePy > Py > 2-MePy > 2,6-MePy. This trend was interpreted in terms of steric effects and the basic strengths of these molecules towards boron trifluoride.     

Regioselective synthesis of 2-unsubstituted 1-aryl-4- and 1-aryl-5-acylimidazoles

An efficient and simple method for the synthesis of 2-unsubstituted 1-aryl-4- and 1-aryl-5-acylimidazoles has been developed. It consists in the condensation of α-diketone monooximes with aromatic amines and formaldehyde on the presence of boron trifluoride etherate, leading to the formation of stable boron trifluoride complexes of N-oxides. Further reduction of these complexes led to the corresponding imidazoles. This method permits broad variations of substituents in the aryl part of these compounds.     

Synthetic utility and mechanistic implications of the Fries rearrangement of hydroquinone diesters in boron trifluoride complexes

Reactions of boron trifluoride methyl and ethyl etherate complexes with hydroquinone diesters yield monomethyl and monoethyl derivatives of acetylhydroquinones. The use of sterically hindered boron trifluoride etherate complexes results in acetylhydroquinone derivatives. This procedure represents a one-step synthesis of acetylhydroquinone derivatives, important building blocks for a variety of synthetic applications.     

Acylation of Cyclopropyl-Substituted Alkenes with Complexes Formed by ω-(Ethylthio)alkanoyl Fluorides and Boron Trifluoride

Cyclopropyl-substituted alkenes react with complexes formed by boron trifluoride and 3-(ethylthio)propionyl fluoride and 2-(ethylthio)acetyl fluoride to give ketones containing an ethylthio group. In most cases the reaction is not accompanied by opening of the three-membered ring or rearrangements.     

Donor-acceptor complexes of linear oligopyrroles with boron trifluoride. Spectral studies and quantum-chemical simulation

Intermediate products of synthesis of the boron trifluoride complexes with linear oligopyrroles are found. By means of electronic spectroscopy it was shown that the reaction of linear oligopyrroles with boron trifluoride in solutions resulted in the formation of stable donor-acceptor complexes. Their composition was established and the formation constants were evaluated. It was shown that transformation of these complexes in the corresponding borofluoride complexes is possible only while boiling the reaction mixture. By means of quantum-chemical methods the structural and energy parameters of the donor-acceptor complexes under study were calculated.     

Structure and Reactivity of Uracil Derivatives. 2. Ambident Nucleophilic Reactivity of 5-Diazouracil

On the basis of 3-21G type ab initio calculations we have studied all the possible complexes of 5-diazouracil with boron trifluoride. The most stable of these are the systems with the BF₃ coordinated at the 3, 9, and 10 positions of the heterocyclic molecule.     

Sur les complexes formés par le trifluorure de bore avec les sulfoxydes,aminoxydes, phosphinoxydes et arsinoxyde: Aspects généraux des spectres de RMN (1H, 11B, 19F et 31P)

Various complexes (R_nMO·BF₃) of boron trifluoride with sulphoxides, aminoxides, phosphinoxides and arsinoxides have been prepared and investigated using proton, fluorine (at variable temperature) boron and phosphorus resonance. A comparison with similar adducts containing a co-ordinative O? B bond is presented.     

Vibrational spectra of the boron halides and their molecular complexes. Part 11. Complexes of boron trifluoride with phosphine and its methyl derivatives. An ab initio study

Ab initio calculations, at the second-order level of M?ller-Plesset perturbation theory, using a triple-zeta Gaussian basis set with polarization and diffuse functions on all atoms, have been carried out on the donor-acceptor complexes of boron trifluoride with phosphine and its mono-, di-, and trimethyl derivatives. The structures, interaction energies, and vibrational spectra of the complexes were determined. The preferred conformer was found to be the staggered species in each case. The computed data were compared with those for some similar complexes containing boron trifluoride and a series of related oxygen, sulfur, and nitrogen bases, and the effect of successive methyl substitution in each series was investigated.     

Reaction of 2-acyloxiranes with cyclic ketones

Acyloxiranes react with cyclopentanone and cyclohexanone in the presence of catalytic amounts of boron trifluoride etherate to give the corresponding 2-acyl-1,4-dioxaspiro[4,4]-nonanes and 2-acyl-1,4-dioxaspiro[4,5]decanes. The corresponding cis-2,3-dimethyl-2 acetyl-1,4-dioxaspiroalkanes are formed from trans-2,3-dimethyl-2-acetyloxirane.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 885–888, July, 1974.     

Polymerization of coordinated monomers. XXI. Ab initio molecular orbital study on the binary molecular complex composed of methyl methacrylate and boron trifluoride

The stereo- and electronic structures of the binary molecular complex composed of methyl methacrylate and boron trifluoride are obtained by using an ab initio molecular orbital method with an STO-3G basis set. The total energy change on the binary molecular complex formation is ?1.3 X 10^?2 Hartree (?8.2 kcal/mol). The electron transfer from methyl methacrylate to boron trifluoride and the change in the energy level of the lowest unoccupied molecular orbital of methyl methacrylate on the complex formation with boron trifluoride are much smaller than those on the complex formation with boron trichloride. A twisted form in which the dihedral angle between the vinyl plane and the ester plane is 16.9° is the most stable structure of the binary molecular complex composed of methyl methacrylate and boron trifluoride. A strong bonding overlap population between a β-hydrogen of methyl methacrylate and a fluorine of boron trifluoride is found in this conformation. © 1992 John Wiley & Sons, Inc.     

α-substituted boron difluoride acetylacetonates

By treatment of α-substituted acetylacetone derivatives with boron trifluoride etherate a series of earlier unknown boron difluoride complexes is obtained. The series includes binuclear complexes containing boron in the chelate fragment connected via sulfur or selenium atom. Gas chromatographic and spectral characteristics of the obtained compounds were investigated. By means of chromato-mass spectrometry their reaction with hydrazine in acidic and alkaline media was studied.     

Synthesis and study of boron trifluoride-based catalytic complex participating in hexafluoropropylene sulfotrioxation

Catalytic complexes of boron trifluoride and sulfuric anhydride were experimentally detected and studied by the ¹⁹F NMR method.