Diastereoselectivity of Azido-Ugi Reaction with Secondary Amines. Stereoselective Synthesis of Tetrazole Derivatives

The diastereoselectivity of azido-Ugi reaction with cyclic amines was investigated. It was found that the reaction with α-substituted five- to seven-membered cyclic amines proceeds very efficiently to provide high control of diastereoselectivity (≤100% de) under mild conditions. Target tetrazole-derived products were isolated in excellent yields (≤98%). The reaction has a broad scope in terms of its amine, aldehyde, and isocyanide nature. It was found that the diastereoselectivity of the reaction depends on the ring size of the starting cyclic amines. More rigid piperidines provided the highest selectivity of the reaction. Using benzyl isocyanide, the prepared N-benzyl tetrazoles can be deprotected by hydrogenolysis to form the corresponding NH tetrazoles in high yields. © 2017 American Chemical Society

Crystal structure of cyclo-tris(μ-3,4,5,6-tetrafluoro-o-phenylene-κ2 C 1:C 2)trimercury-tetracyanoethylene (1/1)

The title compound, [Hg3 (C6F4)3]·C6N4, contains one molecule of tetracyanoethylene B per one molecule of mercury macrocycle A, i.e., A•B, and crystallizes in the monoclinic space group C2/c. Macrocycle A and molecule B both occupy special positions on a twofold rotation axis and the inversion centre, respectively. The supramolecular unit [A•B] is built by the simultaneous coordination of one of the nitrile N atoms of B to the three mercury atoms of the macrocycle A. The Hg⋯N distances range from 2.990 (4) to 3.030 (4) Å and are very close to those observed in the related adducts of the macrocycle A with other nitrile derivatives. The molecule of B is almost perpendicular to the mean plane of the macrocycle A at the dihedral angle of 88.20 (5)°. The donor-acceptor Hg⋯N interactions do not affect the C=N bond lengths [1.136 (6) and 1.140 (6) Å]. The trans nitrile group of B coordinates to another macrocycle A, forming an infinite mixed-stack [A•B]∞ architecture toward [101]. The remaining N atoms of two nitrile groups of B are not engaged in any donor-acceptor interactions. In the crystal, the mixed stacks are held together by intermolecular C - F⋯C=N secondary interactions [2.846 (5)-2.925 (5) Å]

From Cyclic CF3-ketimines to a Family of Trifluoromethylated Nazlinine and Trypargine Analogues

An efficient (one- and two-step) synthesis of trifluoromethylated derivatives of the natural alkaloids nazlinine, trypargine, and homotrypargine was elaborated. Trifluoromethyl-substituted 5-7-membered cyclic imines were used as a masked carbonyl component in the Pictet-Spengler reaction with various tryptamines. As a result, this approach opens access to a family of alkaloid-like compounds bearing a CF3 group at position 1 of tetrahydro-β-carboline. © 2016 American Chemical Society

Crystal structure of cyclo-tris(mu-3,4,5,6-tetrafluoroo-phenylene-kappa C-2(1):C2)trimercury-tetracyanoethylene (1/1)

The title compound, [Hg-3(C6F4)(3)]center dot C6N4, contains one molecule of tetracyanoethylene B per one molecule of mercury macrocycle A, i.e., AeB, and crystallizes in the monoclinic space group C2/c. Macrocycle A and molecule B both occupy special positions on a twofold rotation axis and the inversion centre, respectively. The supramolecular unit [A center dot B] is built by the simultaneous coordination of one of the nitrile N atoms of B to the three mercury atoms of the macrocycle A. The Hg center dot center dot center dot N distances range from 2.990 (4) to 3.030 (4) angstrom and are very close to those observed in the related adducts of the macrocycle A with other nitrile derivatives. The molecule of B is almost perpendicular to the mean plane of the macrocycle A at the dihedral angle of 88.20 (5). The donor acceptor Hg" "o"N interactions do not affect the C=N bond lengths [1.136 (6) and 1.140 (6) Al. The trans nitrile group of B coordinates to another macrocycle A, forming an infinite mixed -stack [A center dot B]infinity architecture toward [101]. The remaining N atoms of two nitrile groups of B are not engaged in any donor acceptor interactions. In the crystal, the mixed stacks are held together by intermolecular C-F center dot center dot center dot C=N secondary interactions [2.846 (5)-2.925 (5) angstrom]

The Structure and EPR Behavior of Nitroxide Biradical Containing Phosphorus Atom in the Bridge

Two short nitroxide biradicals of similar composition: (H5C6)O=P(OR6)2 (BP) and O=S(OR6)2 (BS), where OR6 is 1-oxyl-2,2,6,6-tetramethyl-4-oxypiperidine, have been studied by electron paramagnetic resonance spectroscopy, and X-ray structural analysis. Variations of the intramolecular electron spin exchange in the biradicals, dissolved in toluene, as a function of temperature were characterized by changes in the isotropic 14N hyperfine splitting (hfs) constant a, values of the exchange integral |J|, and compared with the X-ray structural data. Thermodynamic parameters of the conformational rearrangements were calculated. Geometry optimization and spin density distribution calculations of biradical BP were carried out on the DFT/UB3LYPPBE0/cc-pVdTZz and DFT/ROPBE/N07D levels of theory and compared with those of BS. Probable differences in biradicals behavior are discussed. © 2015, Springer-Verlag Wien

Diastereoselectivity of Azido-Ugi Reaction with Secondary Amines. Stereoselective Synthesis of Tetrazole Derivatives

The diastereoselectivity of azido-Ugi reaction with cyclic amines was investigated. It was found that the reaction with α-substituted five- to seven-membered cyclic amines proceeds very efficiently to provide high control of diastereoselectivity (≤100% de) under mild conditions. Target tetrazole-derived products were isolated in excellent yields (≤98%). The reaction has a broad scope in terms of its amine, aldehyde, and isocyanide nature. It was found that the diastereoselectivity of the reaction depends on the ring size of the starting cyclic amines. More rigid piperidines provided the highest selectivity of the reaction. Using benzyl isocyanide, the prepared N-benzyl tetrazoles can be deprotected by hydrogenolysis to form the corresponding NH tetrazoles in high yields. © 2017 American Chemical Society

Synthesis of blue light emitting heterocyclesviacyclization of 2-pyridine derived 4-azido-r1,2,3-triazoles

An efficient synthesis of 2-pyridine derived 4-azido-1,2,3-triazoles was elaborated using the corresponding dichlorodiazadienes as precursors. The reaction of the prepared 2-azine substituted diazadienes with sodium azide permits the preparation of target triazoles isolated in up to 92% yield. Subsequent thermal cyclization was studied. Elimination of molecular nitrogen promoted the cyclization of nitrene at the azine nitrogen. As a result, a family of 2H-[1,2,3]triazolo[4′,5′:3,4]pyrazolo[1,5-a]pyridin-5-ium-4-ides was prepared. The synthesized compounds are members of a new heterocyclic system. Moreover, these compounds are new attractive blue light emitting molecules. © The Royal Society of Chemistry 2021