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Halide-PyBOX complex

Leigh and coworkers developed in parallel a Ni-catalyzed reductive homocoupling of alkyl halides 93 toward an efficient synthesis of rotaxanes (Fig. 22) [122]. In model studies 5-12 mol% of the Ni(II) precatalyst and terpy 8a or (/LA i-Ph-PyBOX 5g sufficed for the coupling of alkyl halides under normal conditions, under which 78-99% of dimers 94 were obtained. A macrocyclic Ni(PyBOX) complex, which has to be present stoichiometrically due to its function as the wheel, serves as the precatalyst in the rotaxane synthesis. Initial reduction of... [Pg.352]

A highly effective Ru-eatalyzed asymmetric intramolecular amination of benzylic and allylic C—H bonds was developed in 2008 by Blakey and coworkers. Ru-Pybox complexes were readily prepared by using Nishiyama s method. Initially, the reaction was tested without any additives. However, the desired product 133 could be produced in only modest yields and ee values (Table 1.10, entries 1-3). Based on the studies by Du Bois, the authors rationalized that a cationic catalyst would be more reactive than the neutral one. Thus, the catalyst prepared from halide abstraction by AgOTf gave improved yields and selectivities (Table 1.10, entries 4-6). Further screening of ligands, solvents, and temperature led to the optimal conditions reaction of sulfamate ester 132 with 5 mol% of C16,110 mol% of PhI(OAc)2, and 230 mol% of MgO in benzene at 4 °C (Table 1.10, entries 7-14). Under these conditions, a series of five- and six-membered-ring products were obtained with up to 71% yield and 92% ee. Notably, the cis-olefin substrate 135 could also participate in the reaction (Scheme 1.50). Under the standard conditions, the... [Pg.46]


See other pages where Halide-PyBOX complex is mentioned: [Pg.152]    [Pg.152]    [Pg.331]    [Pg.135]    [Pg.328]    [Pg.338]    [Pg.61]    [Pg.882]    [Pg.336]    [Pg.338]    [Pg.398]    [Pg.108]    [Pg.125]    [Pg.447]   


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