University of Texas at Austin, Department of Chemistry and Biochemistry, Austin, Texas 78712, USA.
J Am Chem Soc. 2010 Apr 7;132(13):4562-3. doi: 10.1021/ja100949e.
Enantioselective transfer hydrogenation of carbonate 1a in the presence of aromatic, allylic, or aliphatic alcohols 2a-2i employing a cyclometalated iridium C,O-benzoate derived from allyl acetate, 4-cyano-3-nitrobenzoic acid and (S)-SEGPHOS delivers products of (hydroxymethyl)allylation 4a-4i in good isolated yields (60-74%), good anti-diastereoselectivities (5:1-10:1 dr) and exceptional levels of enantiocontrol (93-99% ee). Under identical reaction conditions, but in the presence of isopropanol, aldehydes 3a-3i are converted to an equivalent set of adducts 4a-4i in good isolated yields (58-74%), good anti-diastereoselectivities (4:1-14:1 dr), and exceptional levels of enantiocontrol (95-99% ee). Thus, identical sets of adducts 4a-4i are produced with equal facility from the alcohol or aldehyde oxidation level. These studies represent the first general method for enantioselective carbonyl (hydroxymethyl)allylation, a process that has no highly stereoselective counterpart in conventional allylmetal chemistry.
在芳基、烯丙基或脂肪醇 2a-2i 的存在下,使用源自醋酸烯丙酯、4-氰基-3-硝基苯甲酸和 (S)-SEGPHOS 的环金属化铱 C,O-苯甲酸盐对碳酸盐 1a 进行对映选择性转移氢化,可在良好的分离产率(60-74%)、良好的反非对映选择性(5:1-10:1 dr)和出色的对映体控制水平(93-99%ee)下得到(羟甲基)烯丙基化产物 4a-4i。在相同的反应条件下,但在异丙醇的存在下,醛 3a-3i 被转化为一组相当的加成产物 4a-4i,具有良好的分离产率(58-74%)、良好的反非对映选择性(4:1-14:1 dr)和出色的对映体控制水平(95-99%ee)。因此,从醇或醛氧化水平,以相同的便利性得到相同的加成产物 4a-4i。这些研究代表了对映选择性羰基(羟甲基)烯丙基化的第一个通用方法,这是传统烯丙基金属化学中没有高度立体选择性对应物的过程。