Recent advances in chelation-assisted site- and stereoselective alkenyl C–H functionalization

Abstract

This review highlights recent advances in vicinal- and geminal-group-directed alkenyl C–H functionalizations which proceeded by endo- and exo-cyclometallation.

Regio- and stereo-selective olefinic C–H functionalization of aryl alkenes in ethanol

“…9,10 Notably, the only example using plain 2-vinyl phenol substrates still led to benzoxepine products via β-C–H activation under rhodium catalysis, 10 c and chelation-assisted α-C–H functionalization of styrenes remains a significant challenge. We initially examined a variety of Rh-, Ru-, Ir- and Pd-based catalytic conditions for mono O - or N -chelation-assisted alkenyl C–H functionalization, 1–3 using 2-vinyl benzyl amide/benzamide derivatives, but none of them led to the desired α-/β-functionalized products.…”

“…In the past decade, chelation-assisted olefinic C–H functionalization provided site- and stereo-selective preparation of alkene derivatives or (hetero) cycles that proceeds through five- or six-membered endo -/ exo -metallocycles. 1 There are generally two kinds of functional group-directed olefinic C–H activation reactions. One is the vicinal group directed alkenyl C–H activation that proceeds through five-/six-membered endo -cyclometallation to afford cis -C–H functionalized alkene derivatives.…”

Rh(III)‐Catalyzed Reaction of 2‐Aryl‐3‐acyl‐1H‐indoles with α‐Diazo Carbonyl Compounds: Synthesis of 5‐Carbonyl Substituted Benzo[a]carbazoles via [5+1] Annulation

“…7, 173.7, 157.8 (d, 1 J C-F = 231. 3 Hz),139.6,136.2,129.9,127.7,127.5,126.6,126.5,125.6,124.7 (d,3 J C-F = 10. 5 Hz),122.7,121.9,116.0 (d,4 .30 (dd, J 1 = 7.8 Hz, J 2 = 1.2 Hz, 1H), 3.63 (s, 3H), 3.32 (t, J = 7.2 Hz, 2H), 2.53 (s, 3H), 2.49 (t, J = 7.2 Hz, 2H), 1.99-2.04 (m, 2H).…”

Stereoselective Synthesis of C‐Vinyl Glycosides via Palladium‐Catalyzed C−H Glycosylation of Alkenes

“…Metal-catalyzed directed C À H functionalization of alkenes has recently emerged as an effective strategy to synthesize complex alkenes from easily accessible precursors. [11][12][13][14] Bidentate directing groups have unique ability to harness the reactivity of higher valent metal intermediates to form challenging chemical bonds. [15][16][17] In comparison to arenes, the p reactivity of alkene substrates might more strongly interfere with the C À H cleavage process, posing a challenge to reaction development.…”

“…Notably, the reaction with 5 mol % of Pd catalyst on 1 mmol scale gave 2 in 92 % isolated yield (entry 17). In comparison with iQA, the use of picolinic acid (PA) and other structural analogs gave considerably lower yields (entries [12][13][14]. No product was formed when benzamide was used as the directing group (entry 15).…”