Radical Reactions of the Cobalt-Complexed Propargyl Acetals: Inter- and Intramolecular Variants
作者:Gagik G. Melikyan、Erin Voorhees、Ruth Sepanian
DOI:10.1021/om400718w
日期:2014.1.13
Propargyl acetals are used as a new type of substrate in cobaltocene-induced radical reactions stereodirected by a π-bonded Co2(CO)6 metal core. The experimental protocol involves treatment of the cobalt-complexed acetals with triflic anhydride, an in situ generation of ionic propargyl triflates, and a single-electron, low-temperature reduction of α-alkoxy-stabilized, Co2(CO)6-complexed propargyl cations
炔丙基缩醛在钴茂诱导的由π键结合的Co 2(CO)6金属核定向的自由基反应中用作新型底物。实验方案涉及用三氟甲磺酸酐处理钴配合物的乙缩醛,原位生成离子炔丙基三氟甲磺酸酯,以及单电子,低温还原α-烷氧基稳定的Co 2(CO)6配合物的炔丙基。阳离子。分子间和分子内反应可轻松获得多官能,拓扑多样的3,4-二烷氧基-1,5-炔二炔和3,4-二烷氧基-1,5-环癸二炔,且主要形成相应的d,1-非对映异构体( 73–100%d,l)。发现立体选择性和化学选择性取决于(1)γ取代基的体积大(1,3-位阻;d, 1-73-100%),(2)磷配体的存在会改变π-键合金属核(轴向配体诱导;d, l-91–97%),以及(3)由α烷氧基产生的空间位阻(1,1-空间诱导;d, l - 83–92%)。