Zinc Atom Transfer-Based Silylzincation of Alkynes

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As part of the current interest in "step-economical" processes to progress towards sustainable chemical synthesis, we wish to develop a new radical-based entry to the silylzincation of alkynes. Inexpensive, non-toxic and with high functional group tolerance, organozincs have regained considerable interest from the chemical community as reagents of choice to develop more selective reactions. A specific feature of alkylzincs is that they can react either as polar nucleophiles (carbanions) or transfer homolytically a zinc group (zinc atom radical transfer) to an alkyl radical. The possibility to combine both types of reactivity in a single reaction has made possible recent multi-component radicalbased approaches to the carbozincation of alkenes and alkynes. Following the same strategy, we envision an approach to the silylzincation of alkynes based on a process wherein a silyl radical would add to a carbon-carbon triple bond to produce a vinylic radical that would be reductively zincated by undergoing a zinc atom radical transfer. The dimetallic 1,2-silylzinc species thus produced are expected to be well suited for in-situ functionalization. In a first research axis we will consider the use of silylzinc reagents. The preparation of new silylzinc reagents having silyl substituted silicon units and the study of their aptitude to transfer homolytically a zinc group will be studied prior to considering inter- and intramolecular additions to alkynes. In a second axis, silylzincation reactions using a combination of a silyl radical precursor and a dialkylzinc reagent will be explored, focusing mainly on intramolecular transformations. Finally, in a third part of the project, the use of 1-silyl-2-zincio alkenes as partners in sequential carbon-carbon bond forming metal-catalyzed crosscoupling reactions will be explored.