Ligand-Controlled Regiodivergent Hydrosilylation of Conjugated Dienes Catalyzed by Mono(phosphine)palladium(0) Complexes
Ligand-Controlled Regiodivergent Hydrosilylation of Conjugated Dienes Catalyzed by Mono(phosphine)palladium(0) Complexes
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DOI：
10.1021/acs.organomet.0c00597
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发表时间：
2020-12-18
期刊：
影响因子：
2.8
通讯作者：
Hirano, Masafumi
中科院分区：
文献类型：
--
作者：
Komine, Nobuyuki;Mitsui, Tatsuo;Hirano, Masafumi
单（膦）钯（0）配合物[Pd（eta（2）：eta（2）-C6 H10 O）（PR 3）]（1）催化缺电子共轭二烯与HSiPh 3的氢化硅烷化。在[Pd（eta（2）：eta（2）-C6 H10 O）（PR 3）]（R = Me（1a），Et（1b），OEt（1d），（OPr）-Pr-i（1 e））催化下，戊-2，4-二烯酸甲酯与HSiPh 3的硅氢化反应以定量产率和独有的马氏选择性得到1，2-E产物。与此相反，它们的三苯基膦和-亚磷酸酯类似物，[Pd（？2：？2-C（6）H_（10）O）（PR_3）]（R = Ph（1f），OPh（1g）），主要生成1，4-Z产物（1，2-E/1，4-Z = 3/7）。在2，4-癸烯酸甲酯的氢化硅烷化中的区域选择性也由有机硅烷控制。机制的研究表明，使用一个紧凑的和基本的单磷络合物的反应收益的ChalkHarrod机制，涉及从（？3-烯丙基）（甲硅烷基）钯（II）。弱的供电子单磷配体如P（OPh）（3）使Pd（II）物种不稳定，并促进直接还原消除，得到1，4-Z产物。另一方面，一个紧凑的和给电子的磷配体，如PMe 3，PEt 3，和P（OMe）3，有利于得到更稳定的（？3-烯丙基）（甲硅烷基）钯（II）中间体通过烯丙基旋转，然后还原消除，得到1，2-E产物。
Mono(phosphine)palladium(0) complexes, [Pd(eta(2):eta(2)-C6H10O)(PR3)] (1), catalyze hydrosilylation of electron-deficient conjugated dienes with HSiPh3. Hydrosilylation of methyl penta-2,4-dienoate with HSiPh3 catalyzed by [Pd(eta(2):eta(2)-C6H10O)(PR3)] (R = Me (1a), Et (1b), OEt (1d), (OPr)-Pr-i (1e)) proceeds to give the 1,2-E product in quantitative yield with exclusive Markovnikov selectivity. In contrast, their triphenylphosphine and -phosphite analogues, [Pd(?2:?2-C(6)H10O)(PR3)] (R = Ph (1f), OPh (1g)), mainly produce the 1,4-Z product (1,2-E/1,4-Z = 3/7). The regioselectivity in the hydrosilylation of methyl 2,4-pentadienoate is also controlled by organosilanes. Mechanistic studies suggest that the reaction using a compact and basic mono-phosphorus complex proceeds by the ChalkHarrod mechanism involving the reductive elimination from an (?3-allyl)(silyl)palladium(II). A poor electron-donating mono-phosphorus ligand such as P(OPh)(3) destabilizes a Pd(II) species and promotes direct reductive elimination to give the 1,4-Z product. On the other hand, a compact and electron-donating phosphorus ligand, such as PMe3, PEt3, and P(OMe)3, favors to give the more stable (?3-allyl)(silyl)palladium(II) intermediate by the allyl rotation, followed by reductive elimination to give the 1,2-E product.