Influence of heteroatoms on the extent of double bond pyramidalization

Can, H
Zahn, D
Balcı, Metin
Brickmann, M
The origin of double bond pyramidalization in the series of norbornene and norbornadiene derivatives and the effect of heteroatoms on the magnitude of the double bond bending are reported. For this purpose, equilibrium geometries, vibrational frequencies, and NBO second-order perturbation energies were calculated by use of B3LYP/6-31G** level wave functions. The optimized geometric parameters calculated for norbornadiene are in good agreement with the available experimental results. NBO second-order perturbation analysis has been used to evaluate the effect of hyperconjugative interactions on double bond pyramidalization. In the second part of this study, the interaction of singlet oxygen with 4,5-dioxatetracyclo[,7).0(9,14)]pentadeca- 2(7),9,11,13 -tetra-ene (15) and 4,5,15-trioxatetracyclo[,7).0(9,14)]pentadeca-2(7),9,11,13-tetraene (16) has been studied at the B3LYP/6-31G** level. In the case of addition of singlet oxygen to 15, 4,5,16-trioxapentacyclo[,7).0(9,14)]- hexadeca-9,11,13-triene (17) is produced. It was found that the reaction of singlet oxygen addition to the double bond in 16 does not occur. The degree of pyramidalization in this molecule is similar to the analog 12 {4,5,11-trioxatricyclo[6.2. 1.0(2,7)]undeca-2(7),9-diene}, in which singlet oxygen addition takes place. The reasons of the lack of chemical reactivity with singlet oxygen in 16 are discussed.


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Balcı, Metin; Guney, Murat; Dastan, Arif; Azizoglu, Akin (American Chemical Society (ACS), 2007-06-22)
The bromination of 6,7,8,9-tetrahydro-5H-5,9-ethenobenzo[a][7]annulene yielded regio- and stereospecifically formed dibromides arising from the alkyl shift where the bromine exclusively attacks the double bond from the endo face of the double bond. DFT calculations on model compounds showed that the pyramidalization of the double bond and steric repulsion caused by the methylene protons are responsible for the stereo- and regioselective addition of bromine.
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Zora, Metin (American Chemical Society (ACS), 1993-01-01)
Alkylcarbene-chromium complexes react with cyclobutenediones to give 2-alkoxy-4-cyclopentene-1,3-diones in moderate yield, accompanied by varying amounts of 4-cyclopentene-1,3-dione derivatives which result from reduction of the initial product by the chromium byproduct. The reaction is general for a variety of cyclobutenedione derivatives with alkoxy, alkyl, or aryl substituents. The major products of the reaction between arylcarbene complexes and cyclobutenediones are 5-alkylidenefuranone derivatives. A m...
Study of asymmetric aldol and Mannich reactions catalyzed by proline-thiourea host-guest complexes in nonpolar solvents
Demir, Ayhan Sıtkı; BAŞÇEKEN, SİNAN (Elsevier BV, 2013-04-30)
A proline-thiourea host-guest complex has been described as a good catalyst for asymmetric reactions such as aldol and Mannich reactions. High stereoselectivities were obtained under optimal conditions. Thiourea was observed to have an important effect on the reactivity and selectivity, even in an unconventional nonpolar reaction medium and without the need to utilize low temperatures. This proline-thiourea host-guest system has the ability to participate in a hydrogen bonding network.
One-pot synthesis of chloroalcohols and their lipase mediated kinetic resolution - ferrocenyl aziridinylmethanols as chiral ligands in enantioselective conjugate diethylzinc addition to enones
İşleyen, Alper; Doğan, Özdemir; Department of Chemistry (2007)
An unexpected tricyclic ether formation instead of acetate addition to the double bond of a norbornene derivative aroused our interest to explore the mechanism of this reaction. Mechanistic studies showed that methylene diacetate (MDA) was formed in the stock solution (NBu4OAc + dichloromethane) and decomposed to formaldehyde under Lewis or Brønsted acid conditions. Formaldehyde and olefin condensation (Prins reaction) clearly explains the formation of the unexpected product. Same methodology was then succe...
Chemistry of the benzotropone endoperoxides and their conversion into tropolone derivatives: Unusual endoperoxide rearrangements
Guney, M; Dastan, A; Balcı, Metin (Wiley, 2005-01-01)
The chemistry of two bicyclic endoperoxides, obtained by photooxygenation of 2,3-benzotropone (= 5H-benzocyclohepten-5-one 5) and of its ethyl carboxylate derivative 15, was investigated with the aim of synthesizing the respective benzotropolone derivatives. The reaction of the endoperoxide 10 derived from 5 with thiourea gave the desired benzotropolone, i.e., 6-hvdroxy-5H-benzocyclohepten-5-one (11), in high yield (Scheme 1). On the other hand, the endoperoxide 16 derived from the ethyl carboxylate derivat...
Citation Formats
H. Can, D. Zahn, M. Balcı, and M. Brickmann, “Influence of heteroatoms on the extent of double bond pyramidalization,” EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, pp. 1111–1117, 2003, Accessed: 00, 2020. [Online]. Available: