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Nominated by Peking University as an Excellent Doctoral Dissertation
Describes the synthesis of synthetically useful N-heterocycles using Zr/Si-containing intermediate as a "chemical transformer", which are difficult to synthesize by other means
Presents in detail the determination of X-ray crystal structure, the measurement of activation barrier of aza-Cope rearrangement, as well as the new reaction chemistry of 2,6-diazasemibullvalene (NSBV)
Demonstrates for the first time the localized structure of NSBV as the predominant form and the homoaromatic delocalized structure as a minor component in the equilibrium via theoretical analysis
Research work was highlighted by J. Am. Chem. Soc. Spotlight
In this thesis, the author introduces two strategies used to construct various types of N-heterocycles, based on the chemistry of zirconacycles and 2,6-diazasemibullvalenes. In the first part, the author presents the development of multi-component cyclization of a zirconacyclobutene-silacyclobutene fused compound, nitriles and unsaturated compounds. These reactions provide synthetically useful methodology for various N-heterocycles such as 3-acyl pyrrole, pyrrolo[3,2-d]pyridazine and dihydropyrroloazepine, which are all difficult to synthesize by other means. The isolation and characterization of the key three-fused-ring Zr/Si-containing intermediates are also described in detail. These results show that the zirconacyclobutene-silacyclobutene fused compound behaves as a “chemical transformer” upon treatment with various substrates via the “coordination-induced skeleton rearrangement” mechanism. In the second part, the author demonstrates the synthesis and isolation of a series of 2,6-diazasemibullvalenes (NSBVs) from the reaction of 1,4-dilithio-1,3-dienes and nitriles, highlighting the significant progress made for the first time in this work: (1) determination of X-ray crystal structure of a substituted 2,6-diazasemibullvalene; (2) measurement of the activation barrier of its rapid intramolecular aza-Cope rearrangement in solution; (3) exploration of several reaction types of NSBV with diverse ring-expansion products and “bowl-shape” or “cage-shape” N-containing polycyclic skeletons; (4) demonstration of the localized structure as the predominant form and the homoaromatic delocalized structure as a minor component in the equilibrium using theoretical analysis. Based on well-founded results, this work sheds new light on this controversial topic.