Cp*Co(III)‐Catalyzed C−H Alkenylation of Aromatic Ketones with Alkenes

Abstract

Cost-effective and air-stable high-valent cobalt(III)-catalyzed weakly coordinating, ketonedirected regioselective mono-alkenylation of arenes and heteroarenes with alkenes is demonstrated. Various electron-rich and electron-deficient arenes are tolerated under the reaction conditions, providing E-alkenylated products exclusively. The tertbutyl-acrylates serve as an acrylic acid surrogate to provide cinnamic acid derivatives via direct CÀH alkenylation. A two-step synthesis of a g-PPAR antagonist, the synthesis of indanone, and the modification of divinylsulfone are reported as applications. The mechanistic details suggest a base-assisted intermolecular electrophilic substitution reaction pathway.

Cobalt‐Catalyzed Direct C(sp2)–H Alkylation with Unactivated Alkenes

“…While the desired product was not detected without an acidic additive (entries 1–3), product 3aa was obtained in a 16 % yield with AcOH (2 equiv.) (entry 4), The C(sp 2 )–H alkenylation product 4aa (11 % yield), which is synthesized through the β‐hydride elimination after migratory insertion into alkenes, was also isolated. In the presence of the AgSbF 6 additive, other acids were screened (entries 5–7), and pivOH (pivalic acid) was identified to be the most powerful for linear‐selective C–H alkylation (entry 5).…”

Selective Synthesis of 5‐Alkylated and 5‐Alkenylated Chromones via Catalytic C‐H Coupling of Chromones with Allyl Alcohols

“…White solid (52 mg, 54 % yield), ethyl acetate/petroleum ether = 1 : 5, mp 187-188°C. 1 H NMR (400 MHz, CDCl 3 ) δ: 8.84 (d,J = 16.8 Hz,1H),2H),7.58 (t,J = 9.2 Hz,1H),3H),7.35 (d,J = 9.2 Hz,1H),6.80 (d,J = 16.8 Hz,1H),6.72 (s,1H), 3.91 (s, 3H), 2.50 (s, 3H). 13 C NMR (100 MHz, CDCl 3 ) δ: 201.…”

“…White solid (39 mg, 45 % yield), ethyl acetate/petroleum ether = 1 : 5, mp 157-158°C. 1 H NMR (400 MHz, CDCl 3 ) δ: 9.03 (d, J = 16.4 Hz, 1H), 7.90 (dd, J = 7.2 Hz, J = 2.0 Hz, 2H), 7.68 (t, J = 8.0 Hz, 1H), 7.62 (d, J = 8.0 Hz, 1H), 7.57-7.52 (m, 3H), 7.50 (d,J = 7.2 Hz,1H),6.79 (s,1H),6.48 (d,J = 16.4 Hz, 1H), 2.51 (s, 3H). 13 C NMR (100 MHz, CDCl 3 ) δ: 199.8, 180.0, 162.6, 157.4, 144.3, 137.1, 133.3, 131.9, 131.2, 129.2, 126.4, 124.6, 121.4, 120.0, 108.8, 26.5.…”

Cp*Co(III)-Catalyzed C–H Hydroarylation of Alkynes and Alkenes and Beyond: A Versatile Synthetic Tool

“… 60 In 2019, Maji expanded the scope of the Cp*Co-catalyzed alkenylation reaction to the use of aromatic ketones 96 as directing groups in the reaction of arenes with a variety of acrylates 65 ( Scheme 38 a). 61 After demonstrating that the C–H activation is reversible and not rate determining, the authors were able to detect species XXXV and XXXVI by LC-MS, unraveling the key factor of the mechanism. Besides, it must be mentioned that when the aromatic ketone bearing a 3,4-methylenedioxy group 96h was subjected to the reaction conditions, the alkenylation took place at the most sterically hindered position, leading to the formation of 2-alkenylarenes 97h ( Scheme 38 b).…”