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A versatile Rh( i )-catalyzed C6-selective decarbonylative C–H alkenylation of 2-pyridones with readily available, and inexpensive alkenyl carboxylic acids has been developed. This directed dehydrogenative cross-coupling reaction affords 6-alkenylated 2-pyridones that would otherwise be difficult to access using conventional C–H functionalization protocols. The reaction occurs with high efficiency and is tolerant of a broad range of functional groups. A wide scope of alkenyl carboxylic acids, including challenging conjugated polyene carboxylic acids, are amenable to this transformation and no addition of external oxidant is required. Mechanistic studies revealed that (1) Boc 2 O acts as the activator for the in situ transformation of the carboxylic acids into anhydrides before oxidative addition by the Rh catalyst, (2) a decarbonylation step is involved in the catalytic cycle, and (3) the C–H bond cleavage is likely the turnover-limiting step.
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Microwave‐assisted Rhodium(I)‐Catalyzed C8‐Regioselective C−H Alkenylation and Arylation of 1,2,3,4‐Tetrahydroquinolines with Alkenyl and Aryl Carboxylic Acids
Abstract Rh(I)‐catalyzed C8‐selective C−H alkenylation and arylation of 1,2,3,4‐tetrahydroquinolines with alkenyl and aryl carboxylic acids under microwave assistance have been realized. Using [Rh(CO)2(acac)] as the catalyst and Piv2O as the acid activator, 1,2,3,4‐tetrahydroquinolines undergo C8‐selective decarbonylative C−H alkenylation with a wide range of alkenyl and aryl carboxylic acids, affording the C8‐alkenylated or arylated 1,2,3,4‐tetrahydroquinolines. This method enables the synthesis of C8‐alkenylated 1,2,3,4‐tetrahydroquinolines that would otherwise be difficult to access by means of conventional C−H alkenylation protocols. Moreover, this catalytic system also works well in C8‐selective decarbonylative C−H arylation of 1,2,3,4‐tetrahydroquinolines with aryl carboxylic acids. The catalytic activity strongly depends on the choice of theN‐directing group, with the readily installable and removableN‐(2‐pyrimidyl) group being optimal. The catalytic pathway is elucidated by mechanistic experiments.
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- Award ID(s):
- 2154593
- PAR ID:
- 10641215
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Synthesis & Catalysis
- Volume:
- 366
- Issue:
- 8
- ISSN:
- 1615-4150
- Format(s):
- Medium: X Size: p. 1820-1826
- Size(s):
- p. 1820-1826
- Sponsoring Org:
- National Science Foundation
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