Zinc Atom Transfer-Based Silylzincation of Alkynes
Final Report Abstract
Around 75% of the original objectives of this projects were accomplished and several key obstacles were overcome. This project has provided the proof of concept for a radical approach to silylmetalation and, in a more general sense, elementometalation reactions. Specifically, we demonstrated that organosilyl radical chemistry can be advantageously combined with radical zinc transfer chemistry to develop new methods that provide solutions to current limitations of available anionic or transition-metal-catalyzed approaches. The disclosed protocols for the trans-stereoselective silylzincation of several types of terminal alkynes are a perfect illustration of this point. From a more general perspective, this project demonstrated that a radical behavior similar to that of dialkylzincs can be observed with disilylzinc reagents, provided the silyl group is adequately substituted. This result represents a breakthrough in the field of organozinc chemistry and opens new avenues of research for the functionalization of C–C multiple bonds through multi-component approaches. Indeed, processes such as the silylzincation of alkenes and allenes, which have received much less attention than that of alkynes, should be readily achieved with our radical approach. Furthermore, other radical-based elementozincation reactions (i.e., germylzincation or selenylzincation) can be envisioned through chains propagated by radicals other than silyl radicals (i.e., germyl or selenyl radicals). In-depth understanding and control of the parameters that confer silyl-, germyl-, or selenylzinc reagents a radical or a polar behavior represents the next obstacle to overcome to fully develop the potential of this new chemistry. Finally, extending the radical approach to internal alkynes is also a remaining challenge that was not undertaken in this project. The achievement of the majority of the initial objectives and overcoming of the main technical obstacles represents a positive scientific outcome of this project. Various actions have been useful to provide an international experience to the graduate students involved in the project, which is highly valuable for their higher education. They have also contributed to enhance the cooperation between the two research groups and the emergence of new joint research projects. For instance, a new common application has been submitted.
Publications
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„Trans-Selective Radical Silylzincation of Ynamides“, Angew. Chem. Int. Ed. 2014, 53, 11333–11337
E. Romain, C. Fopp, F. Chemla, F. Ferreira, O. Jackowski, M. Oestreich, and A. Perez-Luna
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„Stereodivergent Silylzincation of α-Heteroatom-Substituted Alkynes“, Org. Lett. 2016, 18, 2054–2057
C. Fopp, E. Romain, K. Isaac, F. Chemla, F. Ferreira, O. Jackowski, M. Oestreich, and A. Perez-Luna
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„Stereodivergent Synthesis of β-Heteroatom-Substituted Vinylsilanes by Sequential Silylzincation–Copper(I)-Mediated Electrophilic Substitution“, Synthesis 2017, 49, 724–735
C. Fopp, K. Isaac, E. Romain, F. Chemla, F. Ferreira, O. Jackowski, M. Oestreich, and A. Perez-Luna
