La[N(SiMe₃)₂]₃‐Catalyzed Hydroboration of Esters and Other Challenging Unsaturated Groups

Abstract

Summary of main observation and conclusion The commercially available homoleptic lanthanum amide La[N(SiMe3)2]3 (LaNTMS) is reported to enable the hydroboration of esters using pinacolborane (HBpin) as the reducing agent. A wide range of substrates including aromatic, aliphatic esters and lactones were applicable to afford corresponding boronic esters in excellent yields under mild and neat conditions with broad functional group compatibility and good chemoselectivity. Furthermore, LaNTMS is capable to realize the very challenging and rarely reported hydroboration of carbonate esters with low catalyst loading at room temperature. Both cyclic and linear carbonate esters can be easily converted to the corresponding products with satisfactory yields. Besides, the hydroboration of alkynes has been developed by using LaNTMS as a catalyst.

Manganese‐Catalyzed Hydroborations with Broad Scope

“… [12b] Catalytic hydroborations of carboxylates have recently been reported with transition metal catalysts, [13] bulky organo‐magnesium,[ 14 , 15 ] amidomagnesium,[ 7a , 16 ] and rare earth metal catalysts. [ 7d , 7e , 17 , 18 ] Catalytic Mn(hmds) 2 enabled clean ester reduction with HBpin at room temperature (Scheme 3 , center). Alkanoates and benzoates were reactive; halides, CF 3 , and heteroaryl substituents were tolerated.…”

“…reported the dibutyl‐magnesium‐catalyzed hydroboration of carbonates at 65 °C in toluene; [30] a Mg I ketiminate complex catalyzed the hydro‐boration of carbonates at room temperature; [16] lanthanum amide catalysts were recently employed by Xue et al. [7d] Following our initial observation of the efficient di‐ n ‐butyl carbonate reduction to methanol and the n ‐butyl borate (Table 1 ), we further explored the scope of this transformation in the presence of 5 mol % Mn(hmds) 2 at room temperature. Acyclic and cyclic carbonates were reduced to methanol (and higher alcohols/diols) in near‐quantitative yields at room temperature with no excess of the reducing reagent (Scheme 4 , center).…”

“…( S )‐(+)‐2‐Methyl butyronitrile was reduced at 50 °C to the β‐chiral butylamine in near‐quantitative yield ( =6.2°, CH 3 OH) [12b] . Catalytic hydroborations of carboxylates have recently been reported with transition metal catalysts, [13] bulky organo‐magnesium, [14, 15] amidomagnesium, [7a, 16] and rare earth metal catalysts [7d–e, 17, 18] . Catalytic Mn(hmds) 2 enabled clean ester reduction with HBpin at room temperature (Scheme 3, center).…”

Manganese‐Catalyzed Hydroborations with Broad Scope

“…Rueping et al. reported the dibutyl‐magnesium‐catalyzed hydroboration of carbonates at 65 °C in toluene; [30] a Mg I ketiminate complex catalyzed the hydro‐boration of carbonates at room temperature; [16] lanthanum amide catalysts were recently employed by Xue et al [7d] . Following our initial observation of the efficient di‐ n ‐butyl carbonate reduction to methanol and the n ‐butyl borate (Table 1), we further explored the scope of this transformation in the presence of 5 mol % Mn(hmds) 2 at room temperature.…”

Synthesis of Zn-Li Bimetallic Compound and Its Catalytic Application in Hydroboration of Isocyanate

“…迄今为止, 唯一的例子是 Roesky 等发现在 2.5 mol%助催化剂 [PhNMe 2 H][B(C 6 F 5 ) 4 ]的共同作用下 2.5 mol% [Zn 2 (η 5 -Cp*) 2 ]能高效催化苯胺和炔的氢氨化反应 [9][10] . 近几年来, 不饱和有机底物硼氢化受到广泛的关注 和研究 [11][12][13][14][15][16][17][18][19][20][21] , 然而对于异腈酸酯硼氢化反应的报道极其 稀少. 2016 年 Warren 和 Grimme 等 [22] 通过大空间位阻异 腈酸酯直接与 Piers 硼烷 HB(C 6 F 5 ) 2 的硼氢化反应合成出 一类新的"受阻路易斯酸碱对"(frustrated Lewis Pairs, FLPs).…”