Palladium catalyzed Carbon–Hydrogen bond activation on amino‐substituted quinones under acidic condition

• Published in: Journal of the Chinese Chemical Society (Taipei) Vol. 68; no. 12; pp. 2337 - 2347
• Main Authors: Huang, Peng‐Hao, Hong, Rui‐Yu, Hong, Fung‐E
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley‐VCH Verlag GmbH & Co. KGaA 01.12.2021; Wiley Subscription Services, Inc
• Subjects: Acetic acid; amino‐group; benzobisoxazole; Chemical synthesis; Chemists; Crystal structure; C–H activation; Hydrogen bonds; Naphthalene; Oxazole; Palladium; quinone; Quinones; Single crystals
• ISSN: 0009-4536; 2192-6549
• DOI: 10.1002/jccs.202100375

In this study, 2‐(benzylamino)naphthalene‐1,4‐dione (4a) was used as the starting material to carry out a one‐pot catalytic reaction in acetic acid with divalent palladium metal Pd(OAc)2 in a nitrogen atmosphere. Two compounds, 5a and 6a, were observed unexpectedly. Both compounds were characterized by spectroscopic methods as well as X‐ray single crystal determination. The crystal structure of 5a reveals that a nitrogen‐containing six‐membered ring is formed; while the crystal structure of 6a shows that both oxazole and pyridine ring are generated. The optimized condition for making 6a was pursued. Derivatives of 4a, such as 4b and 4c, were also used as starting materials to proceed under the aforementioned optimal reaction conditions. Although the yields are not satisfactory, obviously the same patterns of corresponding compounds can be synthesized. The reaction of a 4a‐structural related compound 9 under similar condition, two unexpected oxazole‐containing compounds, 10 and 11, were obtained. The diverse pathways for this type of reactions even starting with slightly different substituents on the quinone indeed provides chemists with a perpetual motivation for further studies. Amino‐substituted naphthoquinones 4a, 4b, and 4c were converted to 5a, 5b, and 5c as well as 6a, 6b, and 6c, respectively, in the presence of Pd(PPh3)4 and acidic condition. Moreover, an amino‐ and amido di‐substituted quinone, 9, was converted to 10 and 11 in similar reaction conditions.