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Pavel K Mykhailiuk - One of the best experts on this subject based on the ideXlab platform.
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difluoro substituted bicyclo 1 1 1 Pentanes for medicinal chemistry design synthesis and characterization
Journal of Organic Chemistry, 2019Co-Authors: Roman M Bychek, Valeriia Hutskalova, Olga A Zaporozhets, Sergey Zozulya, Vadym V Levterov, Pavel K MykhailiukAbstract:A practical synthetic approach to the difluoro-substituted bicyclo[1.1.1]Pentanes was developed. The key step was an addition of difluorocarbene (:CF2) to electron-rich bicyclo[1.1.0]butanes by the...
Waldemar Adam - One of the best experts on this subject based on the ideXlab platform.
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a puckered singlet cyclopentane 1 3 diyl detection of the third isomer in homolysis
Chemistry: A European Journal, 2016Co-Authors: Jianhuai Ye, Waldemar Adam, Sayaka Hatano, Ryohei Kishi, Yusuke Murata, Masayoshi NakanoAbstract:In the photochemical denitrogenation of 1,4-diaryl-2,3-diazabicyclo[2.2.1]heptane (AZ6) bearing sterically hindered substituents, a curious new absorption band at about 450 nm was observed under low-temperature matrix conditions, together with the previously well-characterized planar singlet diradical pl-(1) DR6 with λmax =≈580 nm. The 450 nm species was electron paramagnetic resonance (EPR)-silent. Instead of generating the planar diradical pl-(1) DR6 and the precursor azoalkane AZ6 upon warming, the ring-closed bicyclo[2.1.0]pentane derivative SB6, that is, the AZ6 denitrogenation product was identified. Based on product analysis, low-temperature spectroscopic observations, high-level quantum-mechanical computations, viscosity effect, and laser-flash photolysis, the puckered singlet diradicaloid puc-(1) DR6 was assigned to the new 450 nm absorption. The latter was detected experimentally at the same time as the planar singlet diradical pl-(1) DR6. Sterically demanding substituents as well as viscosity impediments were essential for the detection of the experimentally hitherto unknown puckered singlet cyclopentane-1,3-diyl diradicaloid puc-(1) DR6, that is, the third isomer in homolysis. The present findings should stimulate future work on the mechanistically fascinating stereoselectivity documented in the formation of bicyclo[2.1.0]Pentanes during the 2,3-diazabicyclo[2.2.1]heptane denitrogenation.
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photochemical and chemical electron transfer reactions of bicyclo 2 1 0 Pentanes housanes in solution and in zeolite cavities
Journal of the American Chemical Society, 1996Co-Authors: Waldemar Adam, Avelino Corma, Miguel A Miranda, Mariajose Sabaterpicot, Coskun SahinAbstract:Photochemical electron transfer (PET) and chemical electron transfer (CET) studies have been conducted in solution and within zeolite cavities for the bicyclo[2.1.0]Pentanes (2a−j), prepared by direct photolysis of the corresponding azoalkanes 1. The advantage of the CET oxidations is that they proceed catalytically in a clean manner to afford the rearranged cyclopentenes 3 in excellent yields. A complete reversal in the regioselectivity of the 1,2 migration has been observed for the unsymmetrical derivatives of bicyclo[2.1.0]pentane, namely 2b (methyl substitution) versus 2c,i (phenyl substitution). Both in solution and in the zeolite cavities, the less substituted cyclopentene 3b‘ is obtained for the methyl derivative 2b and the more substituted cyclopentenes 3c,i for the phenyl cases 2c,i. This unexpected fact is rationalized in terms of delocalization of the positive charge into the aromatic ring for the phenyl-substituted radical cation, as corroborated by AM1 calculations. Furthermore, the electron ...
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tris aryl aminium hexachloroantimonates convenient one electron oxidants for chemical electron transfer with bicyclic azoalkanes and bicyclo 2 1 0 Pentanes
Tetrahedron Letters, 1994Co-Authors: Waldemar Adam, Coskun SahinAbstract:Abstract The chemical behavior of the radical cations derived from 2,3-diazabicyclo[2.2.1]hept-2-enes 1 and bicyclo[2.1.0]Pentanes 2 by oxidation with tris (aryl)aminium hexachloroantimonates has been examined.
Coskun Sahin - One of the best experts on this subject based on the ideXlab platform.
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photochemical and chemical electron transfer reactions of bicyclo 2 1 0 Pentanes housanes in solution and in zeolite cavities
Journal of the American Chemical Society, 1996Co-Authors: Waldemar Adam, Avelino Corma, Miguel A Miranda, Mariajose Sabaterpicot, Coskun SahinAbstract:Photochemical electron transfer (PET) and chemical electron transfer (CET) studies have been conducted in solution and within zeolite cavities for the bicyclo[2.1.0]Pentanes (2a−j), prepared by direct photolysis of the corresponding azoalkanes 1. The advantage of the CET oxidations is that they proceed catalytically in a clean manner to afford the rearranged cyclopentenes 3 in excellent yields. A complete reversal in the regioselectivity of the 1,2 migration has been observed for the unsymmetrical derivatives of bicyclo[2.1.0]pentane, namely 2b (methyl substitution) versus 2c,i (phenyl substitution). Both in solution and in the zeolite cavities, the less substituted cyclopentene 3b‘ is obtained for the methyl derivative 2b and the more substituted cyclopentenes 3c,i for the phenyl cases 2c,i. This unexpected fact is rationalized in terms of delocalization of the positive charge into the aromatic ring for the phenyl-substituted radical cation, as corroborated by AM1 calculations. Furthermore, the electron ...
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tris aryl aminium hexachloroantimonates convenient one electron oxidants for chemical electron transfer with bicyclic azoalkanes and bicyclo 2 1 0 Pentanes
Tetrahedron Letters, 1994Co-Authors: Waldemar Adam, Coskun SahinAbstract:Abstract The chemical behavior of the radical cations derived from 2,3-diazabicyclo[2.2.1]hept-2-enes 1 and bicyclo[2.1.0]Pentanes 2 by oxidation with tris (aryl)aminium hexachloroantimonates has been examined.
Pablo Wessig - One of the best experts on this subject based on the ideXlab platform.
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photochemical synthesis of benzoyl spiro 2 2 Pentanes
Photochemical and Photobiological Sciences, 2006Co-Authors: Olaf Muehling, Pablo WessigAbstract:In the present study, we describe the photochemical behaviour of 2-mesyloxy phenyl ketones 8 and 12 bearing a cyclopropane moiety in the side-chain. Irradiation of 8 and 12 leads to the corresponding benzoyl spiro[2.2]Pentanes as a consequence of an initial γ-H-shift, subsequent elimination of MsOH (accompanied by a spin-center shift) and cyclization of the resulting 1,3-diradicals. In contrast, a corresponding phenyl ketone without a mesyloxy group in the 2-position, and thus a potential reactant of the “classical” Norrish–Yang reaction, shows no photochemical reaction. By means of quantum chemical calculations we discovered that in the presence of a mesyloxy group the activation barrier for the photochemical γ-H-shift is substantially decreased. Furthermore, a photoinduced skeletal rearrangement of benzoyl spiro[2.2]pentane to 2-cyclobutylidene–acetophenone could be observed. Compared to the common methods used to synthesize spiro[2.2]Pentanes, the photochemical preparation of benzoyl spiro[2.2]pentane presented herein is the first example where a bond between the spiro atom and an adjacent atom is formed.
Armin De Meijere - One of the best experts on this subject based on the ideXlab platform.
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synthesis of spiro 2 2 Pentanes and spiro 2 3 hexanes employing the me3al ch2i2 reagent
European Journal of Organic Chemistry, 2017Co-Authors: Ilfir R Ramazanov, Rita N Kadikova, Tatyana P Zosim, U M Dzhemilev, Armin De MeijereAbstract:Substituted alkylidenecyclopropanes reacted with 5 equivalents each of Me3Al and CH2I2 at room temperature in hexane to give 1-mono- and 1,1-disubstituted spiro[2.2]Pentanes in high yields. Surprisingly, the same reaction with substituted alkylidenecyclopropanes in CH2Cl2 afforded exclusively 1,1-disubstituted spiro[2.3]hexanes. The transformation of 1,1-diphenylspiro[2.2]pentane into 1,1-diphenylspiro[2.3]hexane was studied with the use of CD2I2 and a plausible mechanism was suggested. The reaction of substituted alkylidenecyclobutanes with the Me3Al/CH2I2 reagent in CH2Cl2 gave only 1,1-disubstituted spiro[2.3]hexanes.
