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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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Rhodium(III)‐Catalyzed C−H Bond Functionalization of 2‐Pyridones with Alkynes: Switchable Alkenylation, Alkenylation/Directing Group Migration and Rollover Annulation
Abstract Cp*Rh(III)‐catalyzed chelation‐assisted direct C−H bond functionalization of 1‐(2‐pyridyl)‐2‐pyridones with internal alkynes that can be controlled to give three different products in good yields has been realized. Depending on the reaction conditions, solvents and additives, the reaction pathway can be switched between alkenylation, alkenylation/directing group migration and rollover annulation. These reaction manifolds allow divergent access to a variety of valuable C6‐alkenylated 1‐(2‐pyridyl)‐2‐pyridones, (Z)‐6‐(1,2‐diaryl‐2‐(pyridin‐2‐yl)vinyl)pyridin‐2(1H)‐ones and 10H‐pyrido[1,2‐a][1,8]naphthyridin‐10‐ones from the same starting materials. These protocols exhibit excellent regio‐ and stereoselectivity, broad substrate scope, and good tolerance of functional groups. A combination of experimental and computational approaches have been employed to uncover the key mechanistic features of these reactions.
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- Award ID(s):
- 1902509
- PAR ID:
- 10226994
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 27
- Issue:
- 34
- ISSN:
- 0947-6539
- Format(s):
- Medium: X Size: p. 8811-8821
- Size(s):
- p. 8811-8821
- Sponsoring Org:
- National Science Foundation
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