Bicyclic strained allenes : incorporation of an allene unit into alpha-pinene and benzonorbornadiene

Date

2009

Author

Kılbaş, Benan

Metadata

Show full item record

Item Usage Stats

171
views

0
downloads

The synthesis of cyclic allenes with eight or less skeletal C-atoms, known as highly strained organic compounds, has for the past decades attracted increasing interest. The first part of study describes an investigation aimed at the incorporation of an allene unit into a natural compound, being α-pinene, by using β-elimination method. The two double-bond isomers 310 and 299b were synthesized as key compounds. Treatment of 310 with t-BuOK resulted in the formation of ketone 308 and diene 313. For the formation of 308, the cyclic allene 300 was proposed as an intermediate. Treatment of 299b, with t-BuOK gave arise to the diene 313 and the dimerization product 322. On the basis of density-functional-theory (DFT) calculations on the allene 300 and the alkyne 320, the formation of the latter as the intermediate was excluded. In the second part of study, the stability of endo-carbene 304 was investigated. Previous studies indicated, during the formation of intermediate 264, no exo-carbene 330 structure could be optimized in its free carbene form. At this point, we were curious about the stability of endo-cyclopropylidene 304 not discussed before in literature. First, addition of bromofluorocarbene to anti-7-ethylbenzonorbornadiene (352) was aimed to isolate the endo-adduct 302b. However, no carbene addition reaction was observed caused by pyramidalization on double bond respect to the methoxy derivative, 363b. Therefore, the bromine was introduced to C-7 carbon atom. Treatment of 302a with MeLi in the presence of furan, gave furan adduct 306a confirmed the formation of allene 305a as a reactive intermediate. Theoretical calculations showed endo-carbene 304a was optimized in the free carbene form . However, it readily isomerizes to allene 305a afforded furan adduct 306a.

Subject Keywords

Chemistry, Organic

URI

http://etd.lib.metu.edu.tr/upload/3/12610317/index.pdf
https://hdl.handle.net/11511/18381

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Chemoenzymatic synthesis of chiral hydroxymethyl cycloalkenols Şenocak, Deniz; Demir, Ayhan Sıtkı; Department of Chemistry (2004) Chiral cyclic alkenols with hydroxymethyl functionality are important structural units in many biologically active natural compouds such as prostaglandins, sesquiterpene antiviral agents, pentenomycins, xanthocidin, sarkomycin, etc. 1,3-cycloalkanediones are converted into bicyclic polyoxo derivatives with formaldehyde and trioxane in the presence of Lewis acid. Selective oxidation of the bicyclic compounds by using manganese(III)acetate followed by enzyme-catalyzed kinetic resolution afforded chiral bicycl...
Enantioselective Michael Addition of Nitroalkanes to Nitroalkenes Catalyzed by Chiral Bifunctional Quinine-Based Squaramides Kanberoğlu, Esra; Tanyeli, Cihangir (Wiley, 2015-10-26) A family of chiral bifunctional acid-/base-type quinine/squaramide organocatalysts is shown to be highly active promoters of the conjugate addition of 1-nitropropane to various trans-β-nitroalkenes. The cooperation of the quinine and the sterically encumbered squaramide moieties catalyzed the Michael addition reactions at 0 °C by using a catalyst loading of only 2 mol % to afford the 1,3-dinitro Michael adducts with excellent enantioselectivity and diastereoselectivity (up to 95 % ee and syn/anti isomers
Naphthazarin-Polycyclic Conjugated Hydrocarbons and Iptycenes Dengiz, Çağatay; GUTIERREZ, Gregory D.; SWAGER, Timothy M. (American Chemical Society (ACS), 2017-07-21) The synthesis of a set of naphthazarin-containing polycyclic conjugated hydrocarbons is described herein. Sequential Diels-Alder reactions on a tautomerized naphthazarin core were employed to access the final conjugated systems. Complete conjugation across the backbone can be achieved through complexation with BF2, as observed by (HNMR)-H-1 analysis and UV/vis spectroscopy. Precise synthetic control over the degree of oxidation of naphthazarin quinone Diels-Alder adduct 10 is additionally demonstrated and e...
ANNULATION REACTIONS OF 4-METHOXY-2-PYRONE WITH VARIOUS ACTIVE METHYL COMPOUNDS Tanyeli, Cihangir (Informa UK Limited, 1989-01-01) Some phenolic biphenyl compounds have been synthesised via the annulation reactions of 4-methoxy-2- pyrone with various active methyl compounds.
ENANTIOSELECTIVE OXIDATION OF THIOANISOLE TO METYL PHENYL SULFOXIDE BY CHIRAL COMPOUNDS BEARING N-Cl BOND İPEK, HALİL; Akdağ, Akın (Informa UK Limited, 2015-08-03) Chiral sulfoxides are used in asymmetric synthesis and are present in various biologically active compounds. Asymmetric synthesis of the sulfoxides has been performed by chiral metal complexes and non-metals containing peroxide and oxide moieties. In this study, a new metal free method has been developed to oxidize thioanisole into methyl phenyl sulfoxide with easily accessible chiral compounds carrying N-Cl bond. For this purpose, chiral amine and amide bearing reagents were synthesized and chlorinated by ...

Citation Formats

B. Kılbaş, “Bicyclic strained allenes : incorporation of an allene unit into alpha-pinene and benzonorbornadiene,” Ph.D. - Doctoral Program, Middle East Technical University, 2009.