Remote control of the diastereoselectivity in the pauson–khand reactions of chiral enynes


Thesis Type: Doctorate

Institution Of The Thesis: Middle East Technical University, Faculty of Arts and Sciences, Department of Chemistry, Turkey

Approval Date: 2011

Thesis Language: English

Student: Serdar Sezer

Supervisor: CİHANGİR TANYELİ

Abstract:

In this thesis, an intramolecular Pauson-Khand reaction of chiral enynes derived from homoallyl, allyl and homopropargyl alcohols is described. For this purpose, 2-heteroaryl substituted homoallyl, allyl and homopropargyl alcohols are easily and efficiently resolved through enzymatic resolution in a high ee (91-99%) with a known stereochemistry. Each enantiomerically enriched enyne derived from homoallyl and homopropargyl alcohols affords the conformationally most stable diastereomeric cyclopenta[c]pyran ring system as a sole product, whereas enantiomerically enriched enynes derived from allyl alcohols give the diastereomeric cis:trans mixture of cyclopenta[c]furan ring system. In addition these, an intramolecular Pauson–Khand reaction of camphor tethered enynes derived from homoallyl, homomethallyl, and homopropargyl alcohols is also described. Accordingly, homoallyl, homomethallyl, and homopropargyl moieties are easily constructed on the camphor carbonyl group with excellent diastereoselectivity due to endo-face selectivity, and with known stereochemistry. Each enantiomerically pure enyne affords the conformationally most stable diastereomeric spirocyclic cyclopenta[c]pyran ring system.