Browsing by Subject "Hypervalent Iodine"

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    2,5-Cyclohexadienones as a Useful Launching Point for the Synthesis of the Briarane Diterpenoids and A Hypervalent Iodine-Mediated Synthesis of Oxazolines
    (2015-05) Moon, Nicholas
    The briarane diterpenoids are a large class of natural products derived from gorgonians and other corals from throughout the world. Despite the extremely large number of briaranes that have been isolated, along with the potent and diverse range of biological activities that have been observed, the total synthesis of the briaranes remains underexplored. A facile synthetic route to the briarane diterpenoids will aid in the further exploration of these molecules. Herein, we will describe a number of synthetic approaches that were evaluated to access a key fragment of the briarane diterpenoids. A key feature of all routes involves the use of 2,5-cyclohexadienone substrates as a diverse platform for the launching of the synthesis. Chapter 1 will provide background information on 2,5-cyclohexadienones. Methods for their synthesis, a survey of their diverse reactivity, and selected examples of their use in natural product synthesis will all be described. Emphasis will be given to reactivity patterns which aided us in our research. Chapter 2 will provide a brief survey of the briarane diterpenoids as well as some of the major biologically active families. Previous synthetic efforts used to access these molecules will also be described. Chapter 3 will describe our efforts to synthesize a key fragment of the briarane diterpenoids (referred to as the briarane stereotetrad) utilizing intermediates containing a bicyclic lactone. Chapter 4 will describe our successful efforts to access the briarane stereotetrad using monocyclic intermediates. The important influence of torsional strain in key steps, as well as a successful route to access the briarane stereotetrad will be described. Chapter 5 will report the results of a separate research project in which an iodine(III) promoted cyclization of N-allylamides to form oxazolines was studied. The development of optimum reaction conditions and the evaluation of the substrate scope will be described. Key results that suggest novel mechanistic details for this electrophilic oxidative cyclization will also be described.
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    Hypervalent Iodine Reagents for Tosyl Transfer Reactions in Organic Synthesis
    (2015-07) Klasen, Scott
    In recent years, organohypervalent iodine compounds have emerged as environmentally friendly and efficient reagents for various synthetically useful oxidative transformations. The purpose of this research is to take a closer look at newer five membered heterocyclic hypervalent iodine compounds similar to the hydroxy(tosyloxy)iodobenzene (HTIB) studied by G.F. Koser in the 1980's, which utilized different variations of iodobenzene with different functional groups in the para-position of a benzene ring in order to perform ligand transfer reactions. Utilizing Koser's framework new heterocyclic hypervalent iodine reagents have been synthesized using 2-iodobenzoic acid as well as other similar substrates as a starting material along with HTIB. Different variations of these heterocycles have been synthesized in order to analyze the structural and kinetic nature of these less studied derivatives and their overall reactivity for selective oxidations and tosyl-transfer reactions in organic synthesis.
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    Water-Triggered Benzyne Generation Using Pseudocyclic Arylbenziodoxaboroles
    (2018-09) Fuchs, Jonathan
    Hypervalent iodine compounds are a broad and hot topic in synthetic organic chemistry. They are much cheaper, more environmentally friendly, and safer to handle then their transition metal counterparts. The largest class of hypervalent iodine belongs to that of the diaryliodonium salts. These compounds are well known arylating reagents and exhibit a wide array of reactivity. One such reaction they are known for is the generation of benzyne, owing to phenyliodine’s leaving ability. It is reported to be a million times better leaving group then triflate. There are several ways to trigger benzyne, the most common and effective are using fluoride anion to desilylate TMS which induces triflate anion to leave. These methods provide mild and convenient methods for producing benzyne. Herein, the first ever generation and subsequent trapping of benzyne using water as trigger from novel pseudocyclic arylbenziodoxaboroles is reported.