Palladium‐Catalyzed C‐H Functionalization of Amido‐Substitued 1, 4‐Napthoquinone in the Presence of Amines toward the Formation of Pyrroles and Imidazoles. Issue 31 (7th November 2017)

• Record Type: Journal Article
• Authors: Chen, Szu‐Wei; Hong, Fung‐E
• Is Part Of: ChemistrySelect. Volume 2:Issue 31(2017)
• Page Start: 10232
• Page End: 10238
• Publication Date: 2017-11-07
• Subjects: Directing group -- Imidazole -- Naphthoquinone -- Ortho- or meta-C−H functionalization -- Pyrrole.; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201702173
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: 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 of4 with newly generated pyrrole rings. Similar reactions were carried out with primary amines and yielded5, having imidazole rings, as well as amination products6 . In the cases of reacting with secondary amines, the route for the formations of4 ‐like, rather than5 ‐type, products were prevailed. As revealed from the crystal structures of4_Bu, 6_Bu, 6_Cy, and4_Cy, cyclization processes indeed took place to form pyrrole and imidazole rings, respectively, which are fused to the former naphthoquinone framework. The crystal structure of5_Cy shows that it is a product from amination reaction. Similar reaction was carried out using PCy3 as the phosphine source and an unexpected product7 was obtained. The crystal structure of7 exhibits that the moiety of PCy3 attaches to the framework of the former naphthoquinone and brings about a new P=C double bond. In addition, the amide fragment of3 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. Abstract : New pyrrole ring could be generated in4 from the Palladium‐catalyzed ortho ‐ C−H functionalization of an amido‐substituted 1, 4‐naphthoquinone, 3, while the reaction was carried out in the presence of tertiary amine and exposed to air. The di‐carbon fragment incorporated in the lately formed pyrrole ring in4 is introduced from the employed tertiary amine. The amido‐substituent in3 is necessary for the success of this type of cyclization reaction.