Understanding the Chemoselectivity in Palladium-Catalyzed Three-Component Reaction of o-Bromobenzaldehyde, N-Tosylhydrazone, and Methanol

Abstract

To understand the ligand-controlled palladiumcatalyzed coupling of o-bromobenzaldehyde, N-tosylhydrazone, and methanol to give methyl 2-benzylbenzoic ester or methyl ether, we herein investigated the mechanisms which account for how C− C and C−O bonds are formed and why bidentate dppf/dppb ligands afford ester, whereas P(o-tolyl) 3 ligand gives ether. The ester chemoselectivity of the bidentate ligands is attributed to the strong electron-donating effect that disfavors the C,Br-reductive elimination of the coupling intermediate of o-bromobenzaldehyde and N-tosylhydrazone.

Divergent Reaction of Isocyanides with o-Bromobenzaldehydes: Synthesis of Ketenimines and Lactams with Isoindolinone Cores

“…Inspired by the above results and previous reports, ,,− we propose a plausible mechanism in Scheme . First, oxidative addition of a C–Br bond to Pd(0) occurred, followed by a coordination/insertion cascade of 2a to generate intermediate B .…”

tBuOK-Promoted Reaction of Selenocyanates and Hydrazones for the Synthesis of Selenoacetals

“…苯基亚甲基-双(苯基硒烷)(3a): 淡黄色液体, 69.9 mg, 产率为 87%. 1 H NMR (400 MHz, CDCl 3 ) δ: 7.45～ 7.39 (m, 4H), 7.29～7.23 (m, 4H), 7.22～7.12 (m, 7H), 5.48 (s, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ: 141.2, 134.5, 131.0, 128.9, 128.3, 128.0, 127.9, 127.5, 43.8 7, 136.9, 121.3, 114.5, 55.2, 54.3, 45.9, 31.8, 25.8 1.64 (ddt,J＝9.7,6.5,3.3 Hz,2H),1.36 (tt,J＝14.3,7.3 Hz,2H), 1.24～1.12 (m, 3H); 13 C NMR (100 MHz, CDCl 3 ) δ: 159.6, 136.8, 136.8, 121.7, 114.6, 56.6, 55.2, 43.6, 31.1, 26.2 3, 137.3, 129.2, 128.2, 126.6, 120.4, 114.6, 55.2, 45.1, 43…”

“…另一方 面, 腙作为一类安全、稳定、易得的卡宾前提, 在有机 合成中占据着十分重要的地位 [9] . Barluenga、王剑波、 梁永民以及黄学良等课题组在这一领域进行了深入系 统的研究 [10][11][12][13][14] . 基于对硒氰酸酯和腙类化合物性质的了 解, 我们设想在碱的促进作用下, 硒氰酸酯产生二硒 醚 [8c] , 随后与原位产生的重氮卡宾作用, 通过经典的斯 蒂文斯重排反应 [15] , 快速地构建硒缩醛骨架, 这种策略 为硒缩醛提供了一种更加快捷高效的合成方法(Scheme 1c).…”

Recent Advances in Palladium-Catalyzed Bridging C–H Activation by Using Alkenes, Alkynes or Diazo Compounds as Bridging Reagents

“…Furthermore, according to their DFT calculations, a different mechanistic pathway was proposed. 63 Namely, after the carbene bridging process, palladium(II)…”