Wang, Bin, authorShi, Yian, advisor2024-03-132024-03-132008https://hdl.handle.net/10217/238013Typically three-membered heterocycles are highly strained molecules. They can exist as stable functional groups or very reactive intermediates. This dissertation discusses three types of three-membered heterocycles including dioxiranes, epoxides, and diaziridines. Dioxirane, a three-membered ring peroxide, is a very powerful oxidant which transfers an oxygen atom to a variety of functional groups including heteroatoms, π-bonds, X-H δ-bonds (X = C or Si), and organometallic compounds. Our group has been interested in the asymmetric epoxidation of unfunctionalized olefins using chiral dioxiranes generated from chiral ketones and Oxone. Asymmetric epoxidation produces chiral epoxides, a very useful three-membered heterocycle, which can be opened and rearranged to form more complex chiral molecules. A glucose-derived ketone with an oxazolidinone moiety has been employed in asymmetric epoxidation of conjugated tri- and tetrasubstituted olefins. The asymmetric epoxidation and subsequent epoxide rearrangement produced the enantioenriched aryl-substituted epoxides, cyclopentanones, cyclobutanones, and γ-butyrolactones in good yields and enantioselectivities. In addition to the above chiral products, chiral allylic alcohols can also be produced via asymmetric epoxidation catalyzed by fructose-derived ketone and base-mediated epoxide isomerization in good yields, high enantioselectivities, and high stereoselectivities. It was proposed that the isomerization of acyclic silyl epoxides to give the (Z)-allylic alcohols proceeds through an unusual silicon-assisted E1cb mechanism based on deuterium-labeling experiments and other observations. A practical synthesis of a diacetate chiral ketone was developed. The application of this diacetate ketone in asymmetric epoxidation of trans- and trisubstituted olefins, as well as its related mechanism, are discussed. A ketone with two oxazolidinone rings proved to be a robust catalyst for asymmetric epoxidation. The catalyst loading can be reduced to 1 mol %, and high enantioselectivities can still be achieved. A glucose-derived ketone with a lactam ring has been employed in the epoxidation of 1,1-disubstituted olefins with good enantioselectivities. Studies indicated that the epoxidation of 1,1-disubstituted olefins with the lactam ketone proceeds mainly via a planar-like transition state. The α, α-dimethyl substituted lactam ketone shows different reactivity from those without substitutions. It is an effective catalyst for asymmetric epoxidation of trans- and trisubstituted olefins. A study on the structural effect of ketone catalysts on asymmetric epoxidation revealed that the nitrogen atom in the spiro ring of the oxazolidinone-containing ketone is an important structural element in asymmetric epoxidation of cis-olefins. N,N'-di-t-butylthiadiaziridine 1,1-dioxide, a nitrogen analogue of dioxiranes, was explored as a nitrogen source for Pd-catalyzed dehydrogenative diamination of unfunctionalized olefin. The diamination is likely to proceed via Pd-catalyzed allylic amination and subsequent cyclization. This diamination is mechanistically distinct from the previously studied process using di-t-butyldiaziridinone as nitrogen source, thus resulting in different regioselectivity.born digitaldoctoral dissertationsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.allylic aminationasymmetric epoxidationchiral dioxiranechiral ketonesdehydrogenative diaminationdiaziridineorganic chemistryTextPer the terms of a contractual agreement, all use of this item is limited to the non-commercial use of Colorado State University and its authorized users.