Structure-Based Rationale for Selectivity in the Asymmetric Allylic Alkylation of Cycloalkenyl Esters Employing the Trost ‘Standard Ligand’ (TSL): Isolation, Analysis and Alkylation of the Monomeric form of the Cationic η<sup>3</sup>-Cyclohexenyl Complex [(η<sup>3</sup>-<i>c</i>-C<sub>6</sub>H<sub>9</sub>)Pd(TSL)]<sup>+</sup>
作者:Craig P. Butts、Emane Filali、Guy C. Lloyd-Jones、Per-Ola Norrby、David A. Sale、York Schramm
DOI:10.1021/ja8099757
日期:2009.7.29
explored computationally. The concave orientated amide N-H is able to activate the leaving group of the allylic ester by hydrogen bonding to its carbonyl group. However, this interaction is only feasible for the (S)-enantiomer of substrate, leading to the prediction of a powerful kinetic resolution (k(S) >> k(R)), as is found experimentally. This new model involving two regiochemically distinct (NH)
阳离子 Pd-eta(3)-烯丙基和 Pd-eta(3)-环己烯基配合物 [Pd(R,R)-1(eta(3)-C(3)H) 单体形式的溶液相结构(5))](+) (7(+)) 和 [Pd(R,R)-1(eta(3)-C(6)H(9))](+) (8(+)) 轴承已通过核磁共振、同位素标记和计算阐明了基于反式环己二胺的 Trost '标准配体' (R,R)-1。在这两种复合物中,(R,R)-1 被发现采用 C(1) 对称构象,导致 13 元螯合物中的凹形,其中手性支架中的一个酰胺基团将其 NH 单元伸出靠近一个烯丙基末端的凹面。相邻的酰胺具有相反的取向,并将其羰基突出到相对烯丙基末端附近的凹面之外。MCHE(2) 对 [8(+)][X(-)] 的化学计量和催化不对称烷基化(E = 酯,M = '护送'反离子,X = Pd 烯丙基反离子)显示出与原位生成催化剂相同的选择性和趋势,并且已经通过计