1. In original plan, to examine the hypothesis for the N-centered radical addition to alkenyl boronates, various nitrogen radical precursors including aryl azides, acyl azides, different amines with polarized N-X bonds (X: I, O, Cl) were synthesized in good to high yields. In our preliminary studies, the reaction conditions were optimized on model vinyl boronic ester with various N-centered radical precursors to identify the best conditions for the construction of desired products. Unfortunately, all the N-centered radical precursors used in the reactions failed to provide the desired products in acceptable yields.
2. In modified plan, we focused on the develop new methodology for the transformation of [1.1.1]propellane: a) a new synthesis of 1,3-disubstituted BCP derivatives through three-component or four-component coupling reactions of [1.1.1]propellane with organometallic reagents and organoboronic esters was achieved. These approaches could be applied to the synthesis of alkenyl-, alkyl-, and aryl-BCP derivatives, and tertiary boronic ester substituted BCPs containing contiguous quaternary centres. This efficient multi-component reaction strategy provides a highly modular approach for the preparation of libraries of structurally diverse BCPs. b) a new strategy for the highly enantioselective construction of α-chiral BCPs in a concise fashion from readily available [1.1.1]propellane was realised. This was accomplished by a highly efficient iridium-catalysed asymmetric allylic substitution of BCP-zinc intermediates readily generated through the reaction of Grignard reagents, [1.1.1]propellane and ZnCl2 in situ, which provided a versatile synthetic handle for the preparation of a diverse range of highly functionalized α-chiral BCPs. c) a new approach to methylenespiro[2.3]-hexane derivatives via a nickel-catalysed cyclopropanation of alkenes with [1.1.1]propellane was developed. This nickel-catalyzed process unveils a new reaction mode that will enhance the application of [1.1.1]propellane in the synthesis of complex molecules.
3.As the first authorship, the results from this fellowship have produced three high-quality articles in international journals including JACS, Angew, and Org. Lett., which will give high visibility to our novel concept to inspire the global chemical community. The fellow attended the following two conferences: Youth Forum in East China Normal University (invited speaker, Shanghai, April, 2019) and the 7th International Forum of Huazhong University of Science and Technology for Outstanding Young Talents (invited speaker, Wuhan, December, 2019). In the dissemination activities, the projects were presented to outstanding young chemists from different countries, and European Union has been acknowledged following the rules detailed in the EU Horizon-2020 portal. The fellow has attended the Bristol Synthesis Meeting in the year 2019. During this meeting held in the UoB, the fellow introduced his projects to the most influential international academics.
