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Synthetic Studies Directed toward Light Driven Molecular Motors
AuthorSahteli, Krishna Prasad
AdvisorBell, Thomas W
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AbstractChapter 1 of this dissertation describes a project directed toward the synthesis of a photon driven artificial molecular motors. The motor consists of a dibenzofulvene rotor sterically geared into a chiral stator derived from trioxaadamantane. The rotor is actuated by light absorption with subsequent isomerization about the exocyclic double bond of the dibenzofulvene rotor. Because this torsional motion is geared into a chiral stator, there exists the possibility for preferential clockwise or counter-clockwise rotation. Motor II and Motor III were designed as synthetic targets. Motor II contains a stator consisting of 2,4,9-trioxaadamantane with substituents at positions 1, 2, 3, 5, 6, 8, and 10, while Motor III contains a stator consisting of 2,4,9-trioxaadamantane with substituents at positions 6, 8, and 10. The stator of Motor III was successfully synthesized as a diastereomeric mixture. The main synthetic route includes Steglich esterification, Ireland-Claisen rearrangement, ring closing metathesis, ozonolysis, and acid catalyzed intramolecular tricyclization. Chapter 1 also describes repeated synthesis of (E)-2-cyano-9-(2,2,2-triphenylethylidene)fluorene, (Z)-2-cyano-9-(2,2,2-triphenylethylidene)fluorene, (E)-2-cyano-9-(2,2,2-triphenylethylidene)fluorene, and (Z)-2-amino-9-(2,2,2-triphenylethylidene)fluorene as models of Motor I. The main synthetic route includes oxidation, Wittig reaction, Rosenmund-von Braun reaction, Buchwald-Hartwig cross coupling reaction, and an addition-elimination with trityl anion to give the desired molecules. Chapter 2 of this dissertation describes a project on the novel synthesis of Motor II and Motor III for photoisomerization studies. The models synthesized are: (E)-2-nitro-9-(2,2,2-trimethylethylidene)fluorene, (Z)-2-nitro-9-(2,2,2-trimethylethylidene)fluorene, (E)-3-nitro-9-(2,2,2-trimethylethylidene)fluorene, and (Z)-3-nitro-9-(2,2,2-trimethylethylidene)fluorene. The main synthetic route includes acylation of fluorene, reduction, elimination, nitration, Sonogashira coupling reaction, palladium-catalyzed cross-coupling reaction, and oxidation. The molecules reported in both chapters were synthesized with reasonable purity and were characterized thoroughly using NMR, GC-MS, ESI-MS, IR, as well as combustion microanalysis or high resolution MS.