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Palladium‐Catalyzed C‐H Functionalization of Amido‐Substitued 1,4‐Napthoquinone in the Presence of Amines toward the Formation of Pyrroles and Imidazoles
Author(s) -
Chen SzuWei,
Hong FungE
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201702173
Subject(s) - chemistry , amination , pyrrole , palladium , reactivity (psychology) , medicinal chemistry , moiety , catalysis , amide , phosphine , crystal structure , double bond , imidazole , stereochemistry , organic chemistry , medicine , alternative medicine , pathology
Transition metal‐catalyzed ortho ‐ C−H functionalization of amido‐substituted 1,4‐naphthoquinone, 3 , in the presence of Pd(OAc) 2 and tertiary amines led to the formations of 4 with newly generated pyrrole rings. Similar reactions were carried out with primary amines and yielded 5 , having imidazole rings, as well as amination products 6 . In the cases of reacting with secondary amines, the route for the formations of 4 ‐like, rather than 5 ‐type, products were prevailed. As revealed from the crystal structures of 4_Bu , 6_Bu , 6_Cy , and 4_Cy , cyclization processes indeed took place to form pyrrole and imidazole rings, respectively, which are fused to the former naphthoquinone framework. The crystal structure of 5_Cy shows that it is a product from amination reaction. Similar reaction was carried out using PCy 3 as the phosphine source and an unexpected product 7 was obtained. The crystal structure of 7 exhibits that the moiety of PCy 3 attaches to the framework of the former naphthoquinone and brings about a new P=C double bond. In addition, the amide fragment of 3 is hydrolyzed and reduced and forms C=N double bond. Here, distinct reactivity of amines from that of phosphines in this type of reactions have been manifested.