Date of Graduation
Eberly College of Arts and Sciences
Kung K Wang
A four-step synthetic sequence was used to prepare 10-(1, 1-dimethylethyl)-5-thienyl-11 H-benzo[b]fluorene from pivalophenone. The key step of the synthetic sequence involved the Schmittel cascade cyclization reaction of the corresponding benzannulated enyne-allene having a thienyl substituent at the alkynyl terminus. The benzannulated enyne-allene was prepared by an initial condensation of pivalophenone with the lithium acetylide derived from 2-iodophenylethyne to form 3-(2-iodophenyl)-1-(1, 1-dimethylethyl)-l-phenyl-2-propyn-1-ol. Reduction of the propagylic alcohol with triethylsilane in the presence of trifluoroacetic acid then furnished 1-(1,1-iodophenyl)-3-(1, 1-dimethylethyl)-3-phenyl-1-propyne. The Sonogashira reaction with 2-ethynylthiophene then produced the corresponding 10-(1, 1-dimethylethyl)-5-thienyl-11H-benzo[b]fluorene from pivalophenone. Similarly, starting from benzophenone, 10-phenyl-5-thienyl-11 H-benzo[b]fluorene was obtained.;The X-ray crystallographic structure of 10-(1,1-dimethylethyl)-5-thienyl-IIHbenzo[ b]fluorene shows that the thienyl substituent has a perpendicular orientation relative to the backbone of the benzofluorenyl system. As a result, the hydrogen atom on carbon-4 is in the magnetically shielded region of the thienyl ring current and thus shows an upfield-shifted signal at delta 6.45.;The successful Sonogashira reaction between 2,6-bis[(4R)-4,5-dihydro-4-phenyl-2- oxazolyl]-4-ethynylpyridine and iodobenzene is a promising way of making benzannulated enediynes bearing pyridine-2,6-bisoxazoline (pybox) ligands at the acetylenic position leading to benzofluorenyl systems possessing pybox moieties. Such heteroaromatic compounds are potentially useful for enantioselective reactions and for asymmetric catalysis.
Makaya, Doreen, "Synthesis of Benzofluorenyl Derivatives Bearing Thiophene Substituents" (2012). Graduate Theses, Dissertations, and Problem Reports. 4892.