Regioselectivity in the Ene reaction of singlet oxygen with cyclic alkenes and application of Ene reaction to stereoselective synthesis of carbaheptopyranose derivatives

Doğan, Şengül Dilem
In the first part of this thesis is related to the regioselectivity in ene reaction of singlet oxygen with cyclic alkenes. The photooxygenation of 1-methyl-, 2,3-dimethyl-, 1,4-dimethylcyclohexa-1,4-dienes, 1,2,3,4,5,8-hexahydronaphthalene (16) and 2,3,4,7-tetrahydro-1H-indene (17) which are readily available through Birch reduction, yielded the ene products. The formed endocyclic dienes were trapped by the addition of singlet oxygen to give corresponding bicyclic endoperoxy-hydroperoxides. In the case of 1-methylcyclohexa-1,4-diene (13) and 1,4-dimethyl-cyclohexa-1,4-diene (15), cis-effect determined the product distribution. Photooxygenation of 2,3-dimethylcyclohexa-1,4-dienes (14) gave mainly exocyclic olefin, which was attributed to the lowered rotational barrier of the methyl group and increased reactivity of the methyl groups. Photooxygeneation of 1,2,3,4,5,8-hexahydronaphthalene (16) and 2,3,4,7-tetrahydro-1H-indene (17) shows importance of the geometry of the allylic hydrogen in the ground state. In the second part of this thesis is related to the stereoselective synthesis of carbaheptopyranose derivatives. Two new carbaheptopyranoses, 5a-carba-6-deoxy-α-DL-galacto-heptopyranose (184) and 5a-carba-6-deoxy-α-DL-gulo-heptopyranose (185) have been prepared starting from cyclohexa-1,4-diene. The addition of dichloroketene to cyclohexa-1,4-diene followed by subsequent reductive elimination and Baeyer-Villiger oxidation formed the bicyclic lactone 188. Reduction of the lactone moiety followed by acetylation gave the diacetate 182b with cis-configuration. Introduction of additional acetate functionality into the molecule was achieved by singlet oxygen ene-reaction. The formed hydroperoxide 189 was reduced and then acetylated. The double bond in triacetate was further functionalized either by direct cis-hydroxylation using OsO4 or epoxidation followed by ring-opening reaction to give the hepto-pyranose derivatives 184 and 185.


Electrochemical and chemical oxidation of K(C2H5OCS2),[Ni(C2H5OCS2)(2)] and [N(C2H5)(4)][Ni(C2H5OCS2)(3)]
Dag, O; Önal, Ahmet Muhtar; Isci, H (1996-06-26)
Electrochemical and chemical oxidation of (Et-Xan(-)), [Ni(Et-Xan)(2)] and [Ni(Et-Xan)(3)](-) (Et-Xan(-) = C2H5OCS2- have been studied by Cyclic Voltammetry and in situ UV-Vis spectroscopy in acetonitrile at room temperature. Cyclic Voltammograms (CV) of Et-Xan(-) and Ni(Et-Xan)(2) display one (0.00 V) and two (0.35 and 0.80 V) irreversible oxidation peaks, respectively, referenced to Ag/Ag+(0.10 M) electrode. However, CV of Ni(Et-Xan)(3)(-) displays one reversible (-0.15 V) and two irreversible (0.35, 0.80...
Electrochemical copolymerization of thiophene containing pseudo-polyether cages with pyrrole
Cihaner, Atilla; Önal, Ahmet Muhtar (2006-01-01)
Conducting copolymers were synthesized via the electrochemical oxidation of pyrrole (Py) in the presence of the monomer 1,12-bis(2-thienyl)-2,5,8,11-tetraoxadodecane (1). The presence of monomer I in the electrolytic solution greatly changed the CV behavior of Py during its potensiodynamic polymerization. The electroactivity of poly(I-co-Py) increased with the increasing amount of I in the comonomer mixture. Copolymer films were prepared via constant potential electrolysis in an electrolytic solution contai...
Regioselectivity observed in manganese(III) acetate mediated addition of acetylacetone to various alkenes: mechanistic and theoretical studies
Ceyhan, Selin; Cetinkaya, Yasin; Akdağ, Akın; BALCI, METİN (2016-10-27)
Various alkenes substituted at the 1,2-positions by 2-thiophenyl, 3-thiophenyl, and phenyl substituted by electron-withdrawing and electron-donating groups were treated with acetylacetone in the presence of Mn(OAc)(3) in acetic acid. In cases where the thiophene ring was connected at the C-2 carbon atom to the double bond, a single regioisomer was formed whereas in case of substitution at the C-3 positions two regioisomers were formed. Stilbene derivatives also gave two regioisomers under the same reaction ...
Electrochemical copolymerization of 2-substituted thiophene derivative linked by polyether bridge with thiophene
Cihaner, A; Önal, Ahmet Muhtar (2005-09-01)
New conducting copolymers have been synthesized via electrochemical oxidation of thiophene (Th) in the presence of monomer bis(2-thienyl)ethyl (1). Cyclic voltammetry (CV) studies showed that the presence of monomer I in the electrolytic solution greatly changes the CV behaviour of the formation of the polythiophene films. It is found that the increasing ratio of I was found to decrease electroactivity of copoly(I-Th). Electrochemical synthesis of copolymer films was achieved via constant potential electrol...
Mass dispersion in transfer reactions with a stochastic mean-field theory
Washiyama, Kouhei; Ayik, Sakir; Lacroix, Denis (2009-09-01)
Nucleon transfer in symmetric heavy-ion reactions at energies below the Coulomb barrier is investigated in the framework of a microscopic stochastic mean-field theory. Although mean field alone is known to significantly underpredict the dispersion of the fragment mass distribution, a considerable enhancement of the dispersion is obtained in the stochastic mean-field theory. The variance of the fragment mass distribution deduced from the stochastic theory scales with the number of exchanged nucleons. Therefo...
Citation Formats
Ş. D. Doğan, “Regioselectivity in the Ene reaction of singlet oxygen with cyclic alkenes and application of Ene reaction to stereoselective synthesis of carbaheptopyranose derivatives,” Ph.D. - Doctoral Program, Middle East Technical University, 2010.