摘要：

Part I: Transition metal catalyzed allene cycloisomerizations provide rapid entry into five-membered carbocyclic frameworks, a common motif in various natural products and pharmaceuticals. Site- and regiocontrolled Au-catalyzed allene cycloisomerizations furnish highly substituted cyclopentenes in >1:1 dr. Significant substitution on the allene substrate is tolerated, with potential to install five contiguous stereocenters after alkene functionalization. Major challenges included identifying a Au/Cu catalyst system that controls the relative rates of allene epimerization, cycloisomerization, and the facial selectivity of a metal enolate addition to the activated allene complex.Similarly, Pd(0) catalysts facilitate the cycloisomerization of allenes to prepare substituted cyclopentene motifs. While both Au(I) and Pd(0)-catalyzed allene cycloisomerizations give 5-endo-dig cyclization, Pd catalysts typically prefer the syn diastereomer in contrast to the anti isomer observed with Au. The change in stereoselectivity is proposed to arise from buildup of A strain during the key carbopalladation step to furnish the cycloisomerized products in moderate to good dr with yields comparable to Au(I) catalysts. Additional developments with Pd(0) catalysts have allowed for the regiocontrolled formation of two new C-C bonds via a tandem carbopalladation/cycloisomerization strategy. Experiments to achieve stereodivergent cyclizations and transform key cyclopentenes into useful synthetic building blocks are described.Part II: Previous work with bis-crown ether motifs linked by a photoswitchable azobenzene moiety have demonstrated the ability of this class of molecules to facilitate ion transport in liquid membranes in a photocontrollable manner. Methods to prepare these compounds are often unreliable and result in low yields, hindering further study of their intrinsic properties. An optimized route to these compounds has led to significant improvements in both yield and reproducibility, in turn allowing for the investigation of their transport abilities in synthetic bilayers. Additionally, the preparation and evaluation of compounds derived from 4,13-diaza-18-crown-6 motifs that are hypothesized to exhibit channel-like behavior are described. Initial studies indicate that lariat ethers derived from these motifs act primarily as lytic agents as opposed to synthetic ion channels.

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