Beilstein J. Org. Chem.2021,17, 1518–1526, doi:10.3762/bjoc.17.109
undoubtedly the result of the lengthy syntheses of these compounds. We report the simple synthesis of a rare example of a non-symmetric [2.2]metaparacyclophane. Treatment of [2.2]paracyclophane under standard nitration conditions gives a mixture of 4-nitro[2.2]paracyclophane, 4-hydroxy-5-nitro[2.2
]metaparacyclophane and a cyclohexadienone cyclophane.
Keywords: cyclophane; metaparacyclophane; nitration; paracyclophane; rearrangement; Introduction
Cyclophanes have been described as having bent and battered benzene rings [1] due to a structure that involves one, or more, aromatic rings linked by aliphatic
one out of the simple [2.2]cyclophane series appears to be [2.2]metaparacyclophane (3). Compared to the other two isomers, there has been scant research [18][19][20][21][22][23] conducted on this framework. A search for the word `[2.2]metacyclophane*` in SciFinder gives 315 hits (192 hits on Web of
Beilstein J. Org. Chem.2015,11, 1274–1331, doi:10.3762/bjoc.11.142
(Scheme 28).
In the literature, there are limited reports on the preparation of cyclophane derivatives by a combination of the Suzuki–Miyaura (SM) coupling and an RCM as key steps. Kotha and Mandal [135] reported a new approach to assemble [1.1.6]metaparacyclophane derivative 183 via the SM cross coupling
diol 183 gave [1.1.6]metaparacyclophane derivative 184 (Scheme 29).
Using the same approach, a butenyl Grignard reagent was added to compound 181 to generate diol 185. Surprisingly, after the addition of G-II catalyst 13, the two RCM products 186 and 189 were obtained [135]. The outcome of product 189