Zinc Atom Transfer-Based Silylzincation of Alkynes

作为目前对“步骤经济”工艺发展到可持续化学合成的兴趣的一部分，我们希望开发一种新的基于自由基的方法来进行炔烃的硅基锌化反应。有机锌具有价格低廉、无毒、官能团耐受性高等特点，已重新引起化学界的兴趣，成为开发更多选择性反应的首选试剂。烷基锌的一个特殊特征是，它们既可以作为极性亲核试剂(碳负离子)反应，也可以将锌基团(锌原子自由基转移)均溶转移到烷基上。将两种类型的反应性结合在一个反应中的可能性使最近基于多组分的方法能够用于烯烃和炔烃的碳锌化反应。遵循同样的策略，我们设想了一种基于硅基自由基与碳-碳三键加成生成乙烯基自由基的方法，该自由基将通过锌原子自由基转移而被还原镀锌。由此产生的双金属1，2-硅基锌物种有望很好地适合于原位功能化。在第一个研究轴中，我们将考虑硅基锌试剂的使用。具有硅基取代硅单元的新的硅基锌试剂的制备以及它们将锌基团均相转移的能力的研究将在考虑分子间和分子内加成到炔烃之前进行。在第二个轴上，将探索使用硅基前驱体和二烷基锌试剂组合的硅基锌反应，主要集中在分子内转化。最后，在项目的第三部分，将探索使用1-硅基-2-锌烯作为连续碳-碳键形成金属催化的交叉偶联反应的伙伴。

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.