Zinc Atom Transfer-Based Silylzincation of Alkynes

作为目前对可持续化学合成的“阶梯经济”过程的一部分，我们希望开发一种新的基于自由基的烷基锌化方法。由于价格低廉、无毒且具有较高的官能团耐受性，有机锌作为开发更多选择性反应的首选试剂，重新引起了化学界的极大兴趣。烷基锌的一个特殊特征是它们既可以作为极性亲核试剂（碳离子）反应，也可以将锌基团（锌原子自由基转移）均匀地转移到烷基自由基上。在单一反应中结合这两种类型的反应活性的可能性，使得最近以多组分自由基为基础的烯烃和炔的碳锌化方法成为可能。遵循同样的策略，我们设想了一种基于硅基自由基加入碳-碳三键产生乙烯基自由基的方法，乙烯基自由基通过锌原子自由基转移被还原锌化。由此产生的1,2-硅基锌双金属有望很好地适合于原位功能化。在第一个研究轴中，我们将考虑硅锌试剂的使用。在考虑对炔进行分子间和分子内加成之前，将研究具有硅基取代硅单元的新型硅锌试剂的制备及其均聚转移锌基团的能力。在第二个轴，硅基锌化反应使用硅基自由基前体和二烷基锌试剂的组合将被探索，主要集中在分子内转化。最后，在项目的第三部分，将探索在顺序碳-碳键形成金属催化的交叉偶联反应中使用1-硅-2-锌烯烃作为伙伴。

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.