Palladium‐Catalyzed Carbonylative Cross‐Coupling of Aryl Iodides and Alkenyl Bromides with Benzyl Halides under Reductive Conditions

Abstract

A direct and convenient method for the palladiumcatalyzed reductive cross-coupling of aryl iodides or alkenyl bromides and secondary benzyl halides under ambient CO pressure to generate a diverse array of aryl/alkenyl alkyl ketones has been developed. This strategy successfully achieves a three-component carbonylative reaction with Zn as the reducing agent for CÀ C bond formation, overcoming the well-known homocoupling of aryl or alkenyl halides, direct cross-coupling between two different electrophiles and other carbonylative coupling reactions. In addition, this method avoids use of preformed organometallic nucleophiles, such as organo-magnesium, zinc and boron reagents. This approach enables the construction of valuable aryl alkyl/ alkenyl ketone derivatives (60 examples, 56-95% yields).Reactivity studies indicate that in situ formed benzylic zinc reagents are intermediates in the catalytic system.

Cross-Coupling of Benzylic and Aldehydic C–H Bonds via Photocatalytic Tandem Radical–Radical Coupling and Acceptorless Alcohol Dehydrogenation

“…propan-1-one (24). 25 Purified by column chromatography (petroleum ether/ethyl acetate = 60:1−30:1) and isolated in 45% yield (20 mg) as a yellow oil; 1 H NMR (400 MHz, CDCl 3 ) δ 7.86 (d, J = 7.6 Hz 2H), 7.29−7.26 (m, 4H), 7.21−7.16 (m, 3H), 4.66 (q, J = 6.8 Hz, 1H), 2.35 (s, 3H), 1.52 (d, J = 7.2 Hz, 3H) ppm; 13 C{ 1 H} NMR (101 MHz, CDCl 3 ) δ 200.0, 143.6, 141.7, 133.9, 129.2, 129.0, 128.9, 127.8, 126.8, 47.7, 21.6, 19.5 ppm.…”

“…2-Phenyl-1-(m-tolyl)propan-1-one (25). 25 Purified by column chromatography (petroleum ether/ethyl acetate = 60:1−30:1) and isolated in 38% yield (17 mg) as a yellow oil; 1 H NMR (CDCl 3 , 400 MHz) δ 7.77−7.72 (m, 2H), 7.29−7.25 (m, 6H), 7.22−7.18 (m, 1H), 4.69 (q, J = 6.8 Hz, 1H), 2.35 (s, 3H), 1.53 (d, J = 6.8 Hz, 3H) ppm; 13…”

“…propan-1-one (26). 25 Purified by column chromatography (petroleum ether/ethyl acetate = 60:1−30:1) and isolated in 36% yield (16 mg) as a yellow oil; 1 H NMR (CDCl 3 , 400 MHz) δ 7.45 (d, J = 7.6 Hz, 1H), 7.22−7.20 (m, 2H), 7.18−7.07 (m, 6H), 4.45 (q, J = 7.2 Hz, 1H), 2.25 (s, 3H), 1.47 (d, J = 6.8 Hz, 3H) ppm; 13 (4-Methoxyphenyl)-2-phenylpropan-1-one (28). 26 Purified by column chromatography (petroleum ether/ethyl acetate = 60:1− 30:1) and isolated in 33% yield (16 mg) as a colorless oil; 1 H NMR (CDCl 3 , 400 MHz) δ 7.94 (d, J = 9.2 Hz, 2H), 7.29−7.28 (m, 4H), 7.21−7.17 (m, 1H), 6.85 (d, J = 9.2 Hz, 2H), 4.64 (q, J = 6.8 Hz, 1H), 3.80 (s, 3H), 1.51 (d, J = 6.8 Hz, 3H) ppm; 13 C{ 1 H} NMR (CDCl 3 , 100 MHz) δ 198.9, 163.2, 141.9, 131.1, 129.4, 128.9, 127.7, 126.8, 113.7, 55.4, 47.5, 19.6 ppm.…”

“…. 25 Purified by column chromatography (petroleum ether/ethyl acetate = 60:1− 30:1) and isolated in 49% yield (26 mg) as a yellow oil; 1 H NMR (CDCl 3 , 400 MHz) δ 7.90 (d, J = 8.4 Hz, 2H), 7.39 (d, J = 8.4 Hz, 2H), 7.30−7.29 (m, 4H), 7.22−7.19 (m, 1H), 4.68 (q, J = 6.8, 1H), 1.52 (d, J = 6.8, 3H), 1.29 (s, 9H) ppm; 13 C{ 1 H} NMR (CDCl 3 , 100 MHz) δ 199.9, 156. 4, 141.7, 133.8, 128.9, 128.7, 127.7, 126.8, 125.8, 47.4, 35.0, 31.0, 19.6 ppm.…”

Palladium‐Catalyzed Benzylic C(sp3)−H Carbonylative Arylation with Aryl Bromides

“…We assumed that Pd-carbonyl complexes would be key intermediates in the carbonylative coupling reactions. [4,16] Hartwig and co-workers prepared a bidentate phosphine bonded Pd ethylene complex that reacted with CO to form L 2 Pd(CO) 2 . [15,17] Therefore, we set out to synthesize and characterize Josiphos derivatives.…”