Atom transfer radical cyclisations of activated and unactivated N-allylhaloacetamides and N-homoallylhaloacetamides using chiral and non-chiral copper complexes
作者:Andrew J. Clark、Floryan De Campo、Robert J. Deeth、Robert P. Filik、Sylvain Gatard、Nicola A. Hunt、Dominique Lastécouères、Gerard H. Thomas、Jean-Baptiste Verlhac、Hathaichanuk Wongtap
DOI:10.1039/a909666c
日期:——
Activated N-tosyl-2,2,2-trichloroacetamide 6a, N-benzyl-2,2,2-trichloroacetamide 6d, 2,2-dichloroacetamides 6b–c and 6e–f and 2-monohaloacetamides 11a–g undergo efficient 5-exo atom transfer radical cyclisations at room temperature mediated by CuCl or CuBr in the presence of tris(N,N-dimethylaminoethylene)amine 3 (trien-Me6). The efficiency and stereoselectivity of these cyclisations was found to be greater than existing published atom transfer procedures based upon CuCl(bipyridine), RuCl2(PPh3)3 and CuCl(TMEDA)2. The product distribution for the cyclisation onto alkyne 11g was found to be solvent dependent. Attempts to make larger ring sizes by endo cyclisation of N-tosylacetamides 19a–c led to a competing 5-exoipso aromatic substitution into the N-tosyl group followed by re-aromatisation and loss of SO2 to furnish an amidyl radical. Cyclisation of N-homoallylacetamides 25a–d proceeded smoothly to give δ-lactams with a range of catalysts based upon ligands 2 and 26. The stereoselectivity of cyclisation to give γ lactams could be somewhat influenced by using chiral enantiopure copper complexes 28–30 suggesting that the reactions may involve metal-complexed radicals.
活化的N-托烯基-2,2,2-三氯乙酰酰胺6a、N-苄基-2,2,2-三氯乙酰酰胺6d、2,2-二氯乙酰酰胺6b–c和6e–f以及2-单卤乙酰酰胺11a–g在室温下通过CuCl或CuBr以及三(N,N-二甲氨基乙烯)胺3(trien-Me6)的介导,经历了高效的5-exo原子转移自由基环化反应。这些环化反应的效率和立体选择性比现有的基于CuCl(联吡啶)、RuCl2(PPh3)3和CuCl(TMEDA)2的原子转移程序更高。环化反应在炔烃11g上的产物分布发现依赖于溶剂。尝试通过N-托烯基乙酰酰胺19a–c的内环化生成更大环的过程,导致N-托烯基基团发生竞争性的5-exo环置换,随后发生再芳香化并失去SO2,生成酰基自由基。N-同烯丙基乙酰酰胺25a–d的环化顺利进行,得到了一系列基于配体2和26的催化剂的δ-内酯。通过使用手性恩路全纯铜复合物28–30,γ-内酯的环化立体选择性受到一定影响,表明反应可能涉及金属配位自由基。