Sterically and Polarity-Controlled Reactions oftBuLi with PCH-NR Heterocycles: Novel Heterocyclic P- and P,O-Ligands and Preliminary Tests in Transition-Metal Catalysis
作者:Bhaskar R. Aluri、Markus K. Kindermann、Peter G. Jones、Joachim Heinicke
DOI:10.1002/chem.200702016
日期:2008.5.9
reactivity towards addition at the P=C bond. The preferred regioselectivity is tert-butylation at phosphorus, occurring with excellent diastereoselectivity for trans-adducts 3 b and 3 c, but the inverse tert-butylation at C2 to 5 b was also observed. N-Neopentyl groups, with intermediate steric demand, give rise to formation of mixtures in ethers but allow switching either to selective CH lithiation in
(1R)-1,3-Benzazaphospholes 1 ac(吲哚类型的P = CH-NR杂环)与tBuLi发生两种反应,具体取决于N取代基的空间需求和介质的极性。小的N-烷基基团的存在会在2-位诱导CH去质子化,生成杂芳基锂试剂2a和2b,而大体积的N-取代基和非极性溶剂会改变在P = C键处的加成反应性。优选的区域选择性是在磷处的叔丁基化,其对反式加合物3b和3c具有优异的非对映选择性,但是在C2至5b处也观察到了叔丁基化。具有中等空间需求的N-新戊基基团导致在醚中形成混合物,但允许切换为在THF / KOtBu中进行选择性CH锂化或在戊烷中进行加成。更大的N-金刚烷基总是引起优选的加成。使用质子化,甲硅烷基化和羧化将P = CLi-NR,(E)-tBuP-CHLi-NR和LiP-CH(tBu)-NR物种转换为相应的sigma(2)-P或sigma(3) )-P化合物4b和6a,b,