C−H Alkenylation of Pyrroles by Electronically Matching Ligand Control
作者:Hyun Tae Kim、Woohyeong Lee、Eunmin Kim、Jung Min Joo
DOI:10.1002/asia.201800558
日期:2018.9.4
Directing group and substrate control strategies have frequently been employed for the regioselective C−H alkenylation of acid‐ and oxidant‐sensitive pyrrole heterocycles. We developed an undirected, aerobic strategy for the C−H alkenylation of N‐alkylpyrroles by ligand control. For C2‐alkenylation of electron‐rich N‐alkylpyrroles, an electrophilic palladium catalyst derived from Pd(OAc)2 and 4,5‐diazafluoren‐9‐one
Sterically controlled C–H alkenylation of pyrroles and thiophenes
作者:Eunsu Kang、Ju Eun Jeon、Siyeon Jeong、Hyun Tae Kim、Jung Min Joo
DOI:10.1039/d1cc04378a
日期:——
Pd-catalyzed C–H alkenylations targeting the least hindered position of N-alkyl pyrroles and 3-substituted thiophenes, as opposed to electronically controlled approaches, are developed. The steric demand and stable bidentate binding mode of the pyrazolonaphthyridine ligand are key to the success of these sterically controlled alkenylations using oxygen as an oxidant.
Regioselective C−H Functionalization Directed by a Removable Carboxyl Group: Palladium-Catalyzed Vinylation at the Unusual Position of Indole and Related Heteroaromatic Rings
The palladium-catalyzed oxidative vinylation of indole-3-carboxylic acids with alkenes effectively proceeds via directedC-H functionalization and decarboxylation to produce the corresponding 2-vinylated indoles. Similarly, pyrrole-, furan-, and thiophenecarboxylic acids also undergo decarboxylative vinylation.
The ortho-olefination of benzoic acids can be achieved effectively through rhodium-catalyzed oxidative coupling with alkenes. The carboxylic group is readily removable to allow ortho-olefination/decarboxylation in one pot. alpha,beta-Unsaturated carboxylic acids such as methacrylic acid also undergo the olefination at the beta-position. Under the rhodium catalysis, the cine-olefination of heteroarene carboxylic acids such as thiophene-2-carboxylic acid proceeds smoothly accompanied by decarboxylation to selectively produce the corresponding vinylheteroarene derivatives.