Efficient 5-exo-trig atom-transfer radical cyclisation 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 acts as a supplementary activator and reducing agent in a SARA-ATRC process. The protocol was extended to the cyclisation onto alkynes and the formation of -lactams, although these reactions gave lower yields (35–76 %).
Cu° promoted cyclization of unsaturated alpha-halogeno amides to give beta- and gamma-lactams / Clark, A. J.; Duckmanton, J. N.; Felluga, F.; Gennaro, A.; Ghelfi, F.; Hardiman, J. R. D.; Isse, A. A.; Manferdini, C.; Spinelli., D.. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1099-0690. - 2016:14(2016), pp. 2479-2491. [10.1002/ejoc.201600249]
Cu° promoted cyclization of unsaturated alpha-halogeno amides to give beta- and gamma-lactams.
F. Ghelfi;
2016
Abstract
Efficient 5-exo-trig atom-transfer radical cyclisation 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 acts as a supplementary activator and reducing agent in a SARA-ATRC process. The protocol was extended to the cyclisation onto alkynes and the formation of -lactams, although these reactions gave lower yields (35–76 %).
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