Catalysts adamantyl-activated

Figure 18 Targeted mesityl-activated catalysts 50 and 51 and adamantyl-activated catalyst 52...

Figure 21 Adamantyl-activated catalysts with varying anionic ligands...

Figure 22 Variation of the N-aryl group in adamantyl-activated catalysts...

Boron tris(triflate) has also been tested in the adamantylation of benzene and toluene with 1-haloadamantanes [Eq. (5.87)] and2-haloadamantanes.232B(OTf)3 is a highly active catalyst to promote the transformation in very short time under mild conditions to yield isomeric aryladamantanes and adamantane byproduct (Table 5.15). Of the isomeric 1-tolyladamantanes, 1-meto-tolyladamantane predominates, whereas the para isomer is the main product of the 2-tolyladamantanes. The ortho isomers were... 

P methylene-carbon of the adamantyl NHC substituent, leading to product 52, which contains a new five-membered metallacycle. While adamantyl-chelated catalyst 52 demonstrated significantly lower activity at room temperature than 49 or 50, appreciable conversion could be obtained at higher temperatures. Catalyst 52 was tested in CM of allylbenzene and CDAB and, for the first time, high Z-selecfivity was achieved in the CM of allylbenzene and CDAB, where the desired product was formed in up to 90% Z-selectivity (corresponding to an ElZ ratio of 0.12). 

Song and co-workers have taken a variety of aldehydes 344 and treated them with A -adamantyl carbene 1 and trimethylsilyl ketene acetal 345 to produce Mukaiyama aldol products 346 in good yield (Eq. 34) [170], The carbene presumably acts as a Lewis base to activate the silicon - oxygen bond in order to promote reactivity of the enol silane. The catalyst loading can be reduced to as low as 0.05 mol% without a change in yield. 

Excellent activities in the coupling of all kinds of aryl chlorides were achieved by use of catalyst 13 containing the bulky bis(adamantyl)( -butyl)phosphane. TONS of 10 to 2 X 10 were recorded even for non-activated aryl chlorides [23]. Quite recently, phosphine oxides according to the equilibrium in eq. (4) were used with Pd2(dba)3 in the Suzuki coupling of aryl chlorides, while a hydroxyphosphine complex/Ni(COD)2 catalyzes the Kumada coupling of the same substrates [26],... 

Aryl coupling reactions. A highly active catalytic system for Suzuki coupling contains Pd(OAc)2, KF, and di-/-butyl-2-biphenylphosphine. but the most efficient catalyst to date is the combination of Pd(OAc)2 and bis(l-adamantyl)butylphosphine, which is effective to couple deactivated AiCl on very low Pd loading (down to 0.001 mol%) yet showing turnover number in the 10,(X)0-20,(XX) range. Products are obtained in good yields. 

More recently, an improved protocol for palladium-catalyzed alkoxycarbony-lation of aryl chlorides with alkyl formates was developed by Beller and colleagues [225]. In the presence of palladium(II) acetate/n-butylbis(l-adamantyl)phosphine, and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a base, for the first time non-activated chloroarenes could be conveniently carbonylated in good yields (Scheme 2.28). In this report, it has been shown that the catalyst system presented does not need the presence of ruthenium co-catalysts. 

Despite the high Z selectivity exhibited by catalysts 10 and 26 in ROMP, neither catalyst showed an ability to control the tacticity of the formed polymer. Catalysts based on Mo and W are often capable of tacticity control, but Ru-based catalysts have traditionally struggled with this type of selectivity [56]. However, the Grubbs group recently reported that a C-H-activated Ru catalyst, where the adamantyl has been replaced with a tert-butyl group, was capable of tacticity control (Scheme 3.8) [57]. The syndiotactic microstructure of the resulting polymers was confirmed using NMR spectroscopy. 

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