Elusive Terminal Copper Arylnitrene Intermediates

Angewandte Chemie - International Edition

5 years ago

Elusive Terminal Copper Arylnitrene Intermediates

Jeffery A. Bertke, Thomas R. Cundari, Timothy H. Warren, Abolghasem (Gus) Bakhoda, Quan Jiang

We report herein three new modes of reactivity between arylazides N3Ar with a bulky copper(I) β-diketiminate. Addition of N3ArX3 (ArX3=2,4,6-X3C6H2; X=Cl or Me) to [iPr2NN]Cu(NCMe) results in triazenido complexes from azide attack on the β-diketiminato backbone. Reaction of [iPr2NN]Cu(NCMe) with bulkier azides N3Ar leads to terminal nitrenes [iPr2NN]Cu]=NAr that dimerize via formation of a C−C bond at the arylnitrene p-position to give the dicopper(II) diketimide 4 (Ar=2,6-iPr2C6H3) or undergo nitrile insertion to give diazametallocyclobutene 8 (Ar=4-Ph-2,6-iPr2C6H2). Importantly, reactivity studies reveal both 4 and 8 to be “masked” forms of the terminal nitrenes [iPr2NN]Cu=NAr that undergo nitrene group transfer to PMe3, tBuNC, and even into a benzylic sp3 C−H bond of ethylbenzene. Attempts at isolating terminal arylnitrenes [Cu]=NAr result in a dicopper diketimide (see scheme, left) formed through reversible C−C coupling at the para position of the NAr group or acetonitrile insertion to give a diazametallacyclobutene (right). Experimental and theoretical studies reveal that both intermediates serve as “masked” sources of the corresponding terminal nitrene [Cu]=NAr that undergoes nitrene transfer to PMe3, CNtBu, and benzylic C−H bonds.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/anie.201611275