Controllable Rh(III)-Catalyzed C–H Arylation and Dealcoholization: Access to Biphenyl-2-carbonitriles and Biphenyl-2-carbimidates

Abstract

A controllable Rh(III)-catalyzed C−H arylation and dealcoholization of benzimidates with arylboronic esters was developed, delivering various biphenyl-2-carbonitriles and biphenyl-2-carbimidates by simply tuning the reaction conditions. This approach features high efficiency, good functional group tolerance, and easy operation. It also provides an alternative pathway to thoroughly exploit the directing group in transition-metal-catalyzed C−H activations.

Unified Protocol for Fe-Based Catalyzed Biaryl Cross-Couplings between Various Aryl Electrophiles and Aryl Grignard Reagents

“…The product was prepared as described in the typical procedure for 4b and isolated through flash chromatography using petroleum ether/ethyl acetate = 100/1 as a yellow oil in 86% yield (308 mg for 4a , X = Br): R f = 0.39 (petroleum ether/ethyl acetate = 50/1); IR (cm –1 , KBr): 3045, 2369, 2345, 2323, 1653, 1559, 1539, 1507, 1457, 1270, 759, 699; 1 H NMR (CDCl 3 , 500 MHz) δ (ppm) 7.79 (d, J = 7.7 Hz, 1H), 7.67 (t, J = 7.7 Hz, 1H), 7.60–7.58 (m, 2H), 7.55–7.51 (m, 3H), 7.49–7.46 (m, 2H); 13 C­{ 1 H} NMR (CDCl 3 , 125 MHz) δ (ppm) 145.5, 138.2, 133.8, 132.8, 130.1, 128.8, 128.7, 127.5, 118.7, 111.3. Data were consistent with those reported in the literature …”

“…[1,1′-Biphenyl]-2-carbonitrile (4a). The product was prepared as described in the typical procedure for 4b and isolated through flash chromatography using petroleum ether/ethyl acetate = 100/1 as a yellow oil in 86% yield (308 mg for 4a, X = Br): R f = 0.39 (petroleum ether/ethyl acetate = 50/1); IR (cm 33 4.1.2.17. Ethyl [1,1′-Biphenyl]-4-carboxylate (4b).…”

Imidate as the Intact Directing Group for the Cobalt-Catalyzed C–H Allylation

“…In this context, NH-free imidates have recently emerged as reactive directing groups that afford various N-containing heterocycles or carbocycles through directed C–H functionalization reactions (Scheme a). − On the other hand, a few reports − have revealed that the NH-free imidate groups can provide ortho -functionalized products without cyclization (Scheme b,c). Wang and co-workers have reported manganese-catalyzed C–H alkenylation reactions that involve alkynes, while Li and co-workers have developed cobalt-catalyzed C–H fluoroalkenylation reactions .…”

“…However, under the reaction conditions applied in the cases mentioned above, the imidate group undergoes dealcoholization to give ortho -functionalized nitriles, which is due to the intrinsic instability of the NH-free imidate moiety (Scheme b). More recently, Yang and co-workers have reported rhodium-catalyzed oxidative C–H arylation reactions of benzimidates, in which the directing imidate group survives under carefully controlled reaction conditions, although the scope of applicable substrates has not been examined (Scheme c) …”

“…More recently, Yang and co-workers have reported rhodium-catalyzed oxidative C−H arylation reactions of benzimidates, in which the directing imidate group survives under carefully controlled reaction conditions, although the scope of applicable substrates has not been examined (Scheme 1c). 10 Herein, we report that NH-free benzimidates undergo C−H allylations under retention of an intact directing group using a cobalt catalyst 12 and vinylcyclopropanes 13 or allyl carbonate 14,15 as allylating agents (Scheme 1d). To demonstrate the synthetic utility of this protocol, the allylated product, which still contains the reactive imidate group, was subsequently subjected to further C−H functionalization/ cyclization reactions to afford functionalized N-heterocycles.…”