Date of Award
© 2013 Jacob S. Tracy. All rights reserved. This work is freely available courtesy of the author. It may only be used for non-commercial, educational, and research purposes. For all other uses, including reproduction and distribution, please contact the copyright holder.
Bachelor of Arts
Chemistry & Biochemistry
Robert S. Paley
Spiroketals are chemical motifs found in a range of natural products, many of which possess important biological activity. The stereochemistry of the spiro center of a spiroketal can be controlled by an enantiomerically pure planar chiral ƞ⁴-iron(0) tricarbonyl scaffold. This planar chiral scaffold is prepared through the Stille coupling of an appropriately substituted β-stannylenone to an enantiomerically pure iodo vinyl p-tolyl sulfoxide. Planar chirality is installed by preferential complexation of an iron(O) tricarbonyl fragment to the less hindered face of the sulfinyl diene. An appropriately substituted planar chiral spiroketal precursor was treated with acid to result in diastereoselective spiroketalization. Substituent effects on the diastereoselectivity of spiroketalization were explored by installing (R) and (S) stereo genic centers bearing methyl substituents on what will become positions of the B ring of a [6,6]-spiroketal. Using both the I-sulfinyl and 2- sulfinyl diene-S-ones, four enantiomerically pure planar chiral ƞ⁴-iron(0) tricarbonyl spiroketal precursors were prepared. Spiroketalization revealed two matched and two mismatched cases. In the matched cases, the equatorial conformation of the methyl group reinforced the directing effect of the organometallic scaffold. In the mismatched cases, the equatorial conformation of the additional methyl group was found to overwhelm the effects of the planar chiral iron tricarbonyl scaffold. Additionally, attempts were made to synthesize three [6,6,6]-bis-spiroketals utilizing the same element of planar chirality. While attempts to synthesize the desired bis-spiroketal products were unsuccessful, two products obtained represent the first stereoselective synthesis of a [6,6,6] tricyclic oxaspirocycle with cyclic enol ether. In both cases, the resulting oxaspirocycle was formed with 10: I diastereoselectivity.
Tracy, Jacob S. , '13, "Studies on the Diastereoselctive Synthesis of Spiroketals and Bis-spiroketals Utilizing a Planar Chiral Sulfinyl Diene Iron(0) Tricarbonyl Scaffold" (2013). Senior Theses, Projects, and Awards. 207.