Semester

Summer

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Kung K Wang

Abstract

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.

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