Solid-Supported Copper Catalysts for Atom-Transfer Radical Cyclizations: Assessment of Support Type and Ligand Structure on Catalyst Performance in the Synthesis of Nitrogen Heterocycles
摘要:
A range of solid supported pyridinemethanimine 9-11 and polyamine 12-15 ligands have been prepared on silica, polystyrene, and JandaJel supports. The CuCl and CuBr complexes of these supported ligands have been used to assess both the effect of the ligand type and the nature of the support upon a representative range of copper-mediated atom transfer 5-exo-trig 6, 24-25, 5-exo-dig 26, 4-exo-trig 28, and 5-endo-trig 27, 38 radical cyclizations to give nitrogen heterocycles. In addition, the effect of the nature of the support on the stereochemical outcome of the 5-exo cyclization of 25 has been probed. Generally, it was found that the type of support (e.g., polystyrene, silica, or JandaJel) had very little effect upon the efficiency and selectivity of the processes but that the nature of the ligand type immobilized was the important factor. Thus, the 5-exo cyclization of 6 and 24-26 proceeded more rapidly with the PMI ligands 9-11, whereas 4-exo cyclizations 28 and 5-endo, radical polar crossover reactions 27 and 38 proceeded more efficiently with the JJ-TEDETA ligand 15. The efficiency of the supported ligands was also compared to their solution counterparts 4 and 5. The reusability of P-PMDETA ligand system 13 was assessed in the cyclization of 6.
Cu<sup>0</sup>-Promoted Cyclisation of Unsaturated α-Halogeno Amides To Give β- and γ-Lactams
作者:Andrew J. Clark、Jonathan N. Duckmanton、Fulvia Felluga、Armando Gennaro、Franco Ghelfi、Jack R. D. Hardiman、Abdirisak A. Isse、Claudia Manferdini、Domenico Spinelli
DOI:10.1002/ejoc.201600249
日期:2016.5
Efficient 5-exo-trig atom-transfer radicalcyclisation of 13 unsaturated α-halogeno amides mediated by Cu0 (copper wire) with tripyridylmethanimine ligand (TPMA; 1 mol-%) in a mixed solvent of EtOAc/EtOH (3:1) is reported (89–98 %), with recycling of the copper wire. A substantial improvement in conversion and selectivity was obtained when Na2CO3 (5 mol-%) was added to the reaction mixture. The Cu0
Efficient β-lactam synthesis via 4-exo atom transfer radical cyclisation using CuBr(tripyridylamine) complex
作者:Andrew J Clark、Gary M Battle、Andrew Bridge
DOI:10.1016/s0040-4039(01)00737-7
日期:2001.6
The tripyridylamine copper(I) halide complex mediates the atom transfer radicalcyclisation of bromo-enamides to give β-lactams exclusively with no formation of γ-lactams. Initial products 7 arise from 4-exo bromine atom transfer but elimination can be readily achieved by reaction with DBU to furnish alkenes 8 in high yields (92–98%).
Atom-Transfer Cyclization with CuSO<sub>4</sub>/KBH<sub>4</sub>: A Formal “Activators Generated by Electron Transfer” Process Also Applicable to Atom-Transfer Polymerization
作者:Andrew J. Clark、Alana E. C. Collis、David J. Fox、Lauren L. Halliwell、Natalie James、Rachel K. O’Reilly、Hemal Parekh、Andrew Ross、Andrew B. Sellars、Helen Willcock、Paul Wilson
DOI:10.1021/jo301429a
日期:2012.8.17
The 4-exo and 5-exo-trig atom-transfer cyclizations of 1, 8a-e, 9, 12, and 13 can be mediated with as little as 0.05 mol % of Cu(TPMA)SO4 center dot 5H(2)O in the presence of 2.5 mol % of borohydride salts in 10 min at room temperature in air. This formal "activators generated by electron transfer" (AGET) procedure utilizes a cheap and oxidatively stable copper source (CuSO4 center dot 5H(2)O) and can be carried out in environmentally benign solvents (EtOH). It is possible to alter the product distribution in the 5-endo radical-polar crossover reactions of 10a,b and 11 by tailoring the amount of borohydride. Cyclization onto alkynes 14 and 15 is also possible in only 20 min. Controlled radical polymerization of styrene, with increased rates over conventional atom-transfer radical polymerization (ATRP), can be carried out in a controlled fashion (Mn, PDI) using either CuBr or CuSO4 center dot 5H(2)O and Bu4NBH4.