Contents: B. Alcaide ∙ P. Almendros: Novel Aspects on the Preparation of Spirocyclic and Fused Unsual β-Lactams.- S.S. Bari ∙ A. Bhalla: Spirocyclic β-Lactams: Synthesis and Biological Evaluation of Novel Heterocycles.- L. Troisi ∙ C. Granito ∙ E. Pindinelli: Novel and Recent Synthesis and Applications of β-Lactams.- C. Palomo ∙ M. Oiarbide: β-Lactams Ring Opening: A Useful Entry to Amino Acids and Relevant Nitrogen-Containing Compounds.- B. Mandal ∙ P. Ghosh ∙ B. Basu: Recent Approaches Towards Solid Phase Synthesis of β-Lactams.- A.Arrieta ∙ B. Lecea ∙ F.P. Cossio: Computational Studies on the Synthesis of β-Lactams Via [ 2+2] Thermal Cycloadditions.- B. K. Banik ∙ I. Banik ∙ F. F. Becker: Novel Anticancer β-Lactams

This dissertation is focused on the development of new methods to synthesize imidazoline scaffolds. The work discusses three new procedures developed in the Tepe lab to synthesize trans-oxazoline, trans-imidazoline, and 2,3-disubstituted quinoline scaffolds. In addition, a new guanidine base mediated diastereoselective aziridine synthesis is described in this work. These new synthetic methodologies provide access to compounds that were not easily accessible using previously described methods. Paths to oxazolines and imidazolines via modified Corey-Chaykovsky sulfur ylide chemistry are presented. Here, the sulfonium salts were treated with stable precursors of acyl imines and 1,3-diaza-1,3-butadiene intermediates, respectively, for the oxazoline and imidazoline syntheses. A modified Skraup-type reaction was employed to synthesize 2,3-disubstituted quinoline scaffolds where epoxides were treated with aromatic anilines under mild conditions in the presence of a Lewis acid.

Non-metal catalysis may provide new and green methods for obtaining bioactive heterocycles. Many catalysts contain metals, which can be toxic, energy intensive to remove, and require mining of the source materials. By utilizing metal-free catalysts we avoid these issues. This book explores the use of non-metal catalysts when synthesizing various heterocyclic structures with bioactivity.

Abstract: Small, polyfunctionalized heterocycles have attracted significant attention in the design of biologically active compounds in the drug discovery enterprise. Research in the area of combinatorial synthesis employing heterocycles as scaffolds for library development has become very prominent. Pyridine-containing heterocycles, such as tetrahydronaphthyridines, have been shown to possess a variety of biologic activities. Previous work in our group developed an inverse-electron-demand Diets-Alder (IEDDA) strategy to prepare the 1,2,3,4-tetrahydro-1,5-naphthyridines, however, the preparation of the other tetrahydronaphthyridine analogues could not be achieved via this IEDDA strategy. Thus, metal-catalyzed [2 + 2 + 2] cyclizations between a nitrite and two alkynes were investigated in both intermolecular and intramolecular reactions, which have the potential to prepare all the tetrahydronaphthyridine isomers. To determine optimal conditions, different transition metals (Co, Zr, Ni, Ir, Ru, and Au), as well as reaction conditions (thermal heating, photochemical activation, and microwave irradiation) were screened. The best results were achieved when CpCo(CO) 2 was employed as catalyst, under microwave irradiation in chlorobenzene. Using the optimized microwave-promoted conditions, the intermolecular cyclizations between amino alkynyl nitriles and alkynes gave the desired 5,6,7,8-tetrahydro-1,6-naphthyridines in modest yields, while the intramolecular cyclizations of dialkynyl aminonitrile precursors afforded dihydropyran ring-fused tetrahydronaphthyridines in excellent yields. Finally, a heterocyclic natural product, naringenin, was investigated for its suitability as a library scaffold. Belonging to the flavonone class, naringenin is characterized by the rigid tricyclic benzopyran core with three phenols at C-5, C-7 and C-4' positions. Recent epidemiological studies showed increasing evidence for the anticancer and antiatherogenic properties of this natural product. Its rigid, densely functionalized tricyclic scaffold is an attractive structure for discovering novel bioactive molecules. Thus, suitable chemistries were explored on these scaffolds in an effort to define regioselective transformations of the phenolic groups through palladium catalyzed cross-coupling chemistry which could be applied to library development.

This dissertation encompasses several studies pertaining to natural product total synthesis, reaction methodology development, and organic materials. Given that natural product structures inspire the development of new agrochemicals and pharmaceuticals, their syntheses remain a worthwhile pursuit in organic chemistry. Furthermore, the successful completion of a total synthesis endeavor can confirm proposed molecular structures and biological activities, in addition to serving as a testing ground for new synthetic methods. Similarly, organic materials impact many areas of humanity, including technology, health, and energy conversion. Therefore, developing new reaction methodologies is crucial for expanding the architectures, and thereby properties, of organic materials. Specifically, photocatalysts and organic light-emitting diodes (OLEDs) often rely on photophysical properties imparted by N-containing polycyclic aromatic hydrocarbon (PAH) ligands. As such, new methods that provide access to unique N-containing heterocyclic scaffolds are highly desirable. Chapter one offers a current perspective on the field of natural product total synthesis. Although historically viewed as a highly competitive field, several recent syntheses demonstrate a growing spirit of collaboration in total synthesis. By forming alliances with chemists in other fields, industries, or laboratories, total synthesis chemists have made many breakthroughs that would arguably not have been possible if working independently. Chapter two describes our laboratory's total syntheses of several bioactive akuammiline alkaloids, including strictamine, 2(S)-cathafoline, akuammiline, -akuammigine, and 10-demethoxyvincorine. Our strategic approach to the natural products focused on the use of a modern variant of a classic reaction, the Fischer indolization, to install several rings and the common quaternary center found in each target. This strategy allowed for the first total syntheses of akuammilines bearing a methanoquinolizidine core, as well as those that bear vicinal quaternary centers. In addition, rearrangements of the methanoquinolizidine core were developed that allowed us to access pyrrolidinoindoline-containing akuammilines. Chapter three describes synthetic studies of the reactive intermediates 2,3-pyridyne and 4,5-pyrimidyne. Heterocycles bearing one or more nitrogen atom are privileged motifs in natural products and pharmaceuticals. Therefore, methodologies that decorate such heterocycles are of great interest to the synthetic and biological communities. Arynes are highly reactive, transient species that can efficiently build multiple bonds in a single transformation, and our lab is particularly interested in accessing new, heterocyclic arynes to study their reactivity. This study demonstrates the synthetic utility of 2,3-pyridyne and the undesired reactivity of a 4,5-pyrimidyne precursor. Chapter four describes synthetic studies toward the development of new methods to manipulate polypyridyl organometallic scaffolds. Ruthenium- and iridium-based polypyridyl organometallic complexes have been known for nearly a century and have broadly impacted the scientific community, including the areas of catalysis, bioimaging, and energy conversion. Despite decades of study, methods to synthesize polypyridyl ligands are limited to relatively few transformations, particularly when extending -conjugation. We detail the use of arynes to extend the conjugation of polypyridyl ligands "on-the-complex," thereby overcoming traditional limitations in ligand synthesis. We also disclose the first generation and trapping of a ligand-bound aryne on an organometallic complex. Chapter five describes the synthesis of a novel -extended carbazole ligand for the study of structure-property relationships in two-coordinate metal complexes. Recently, linear two-coordinate metal complexes of the general structure donor-metal-acceptor have been identified as promising dopants for OLEDs. Both the donor and acceptor ligand play a crucial role in tuning the photophysical properties of these complexes. However, donor ligands with extended -conjugation have not been studied in this context. Our approach leverages heterocyclic arynes to synthesize -extended donor ligands in a modular fashion, which can also apply to other PAHs. Subsequent photophysical studies of -extended two-coordinate metal complexes identify a new dopant that displays up to 80% photoluminescence efficiency.

The continued successes of large- and small-scale genome sequencing projects are increasing the number of genomic targets available for drug d- covery at an exponential rate. In addition, a better understanding of molecular mechanisms—such as apoptosis, signal transduction, telomere control of ch- mosomes, cytoskeletal development, modulation of stress-related proteins, and cell surface display of antigens by the major histocompatibility complex m- ecules—has improved the probability of identifying the most promising genomic targets to counteract disease. As a result, developing and optimizing lead candidates for these targets and rapidly moving them into clinical trials is now a critical juncture in pharmaceutical research. Recent advances in com- natorial library synthesis, purification, and analysis techniques are not only increasing the numbers of compounds that can be tested against each specific genomic target, but are also speeding and improving the overall processes of lead discovery and optimization. There are two main approaches to combinatorial library production: p- allel chemical synthesis and split-and-mix chemical synthesis. These approaches can utilize solid- or solution-based synthetic methods, alone or in combination, although the majority of combinatorial library synthesis is still done on solid support. In a parallel synthesis, all the products are assembled separately in their own reaction vessels or microtiter plates. The array of rows and columns enables researchers to organize the building blocks to be c- bined, and provides an easy way to identify compounds in a particular well.

Chemical sensors are in high demand for applications as varied as water pollution detection, medical diagnostics, and battlefield air analysis. Designing the next generation of sensors requires an interdisciplinary approach. The book provides a critical analysis of new opportunities in sensor materials research that have been opened up with the use of combinatorial and high-throughput technologies, with emphasis on experimental techniques. For a view of component selection with a more computational perspective, readers may refer to the complementary volume of Integrated Analytical Systems edited by M. Ryan et al., entitled “Computational Methods for Sensor Material Selection”.