Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• materials, and as the basis of the study of through-space conjugation [2][8][9][10][11][12][13][14][15][16]. There are fewer studies of [2.2]metacyclophane (2) and its derivatives. This is probably related to a lack availability as well as the reduced interaction between the aromatic rings [17]. But the odd

• 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

• structure that mix the characteristics of both meta- and paracyclophane [32]. The carbon at the 8-position of the meta ring is forced over the para ring, leading to distinct chemical shifts for substituents. Its strain energy (23 kcal mol−1) places it between [2.2]paracyclophane (1) and [2.2]metacyclophane

Use of mixed Li/K metal TMP amide (LiNK chemistry) for the synthesis of [2.2]metacyclophanes

• Marco Blangetti,
• Patricia Fleming and
• Donal F. O'Shea

Beilstein J. Org. Chem. 2011, 7, 1249–1254, doi:10.3762/bjoc.7.145

• Marco Blangetti Patricia Fleming Donal F. O'Shea Centre for Synthesis and Chemical Biology, School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland 10.3762/bjoc.7.145 Abstract A new two-step general approach to [2.2]metacyclophane synthesis from

• oxidative coupling with 1,2-dibromoethane. The synthetic ease of this approach compares favourably with previously reported methods and allows for ready access to potentially useful planar chiral derivatives. Keywords: benzylic metalation; LiNK chemistry; [2.2]metacyclophane; oxidative coupling; planar

• deuteration gave the di-deuterated product D2-6f. 2H NMR analysis showed no aryl or bridging methylene deuteration, with deuterium incorporated only into the two non-equivalent benzylic methyl positions (Figure 3). With the benzylic metalation confirmed, the second step to complete the [2.2]metacyclophane