Ring Contraction of Tropylium Ions into Benzenoid Derivatives

Abstract

We report a method to convert substituted tropylium ions into benzenoid derivatives.

Pd-Loaded Cellulose NanoSponge as a Heterogeneous Catalyst for Suzuki–Miyaura Coupling Reactions

“…Internal Standard (ACN): 1 H NMR (400 MHz, CDCl 3 ) δ 2.04 (s, 3H); Product 3a (4-Methoxybiphenyl): 1 H NMR (400 MHz, CDCl 3 ) δ 7.55–7.50 (m, 4H), 7.40 (t, J = 7.5, 2H), 7.29 (t, J = 7.3, 1H), 6.97 (d, J = 8.8, 2H), 3.84 (s, 3H) [ 55 ]; Product 3b (3-Methoxybiphenyl): 1 H NMR (400 MHz, CDCl 3 ) δ 7.61 (d, J = 7.5, 2H), 7.45 (t, J = 7.6, 2H), 7.39–7.35 (m, 2H), 7.20 (d, J = 7.7, 1H), 7.15 (t, J = 2.0, 1H), 6.92 (dd, J = 8.2, 2.3, 1H), 3.87 (s, 3H) [ 56 ]; Product 3c (2-Methoxybiphenyl): 1 H NMR (400 MHz, CDCl 3 ) δ 7.54 (d, J = 8.3, 2H), 7.41 (t, J = 7.6, 2H), 7.34–7.31 (m, 3H), 7.03 (t, J = 7.5, 1H), 6.99 (d, J = 8.5, 1H), 3.81 (s, 3H) [ 56 ]; Product 3d (4-Methylbiphenyl): 1 H NMR (400 MHz, CDCl 3 ): δ = 7.64 (d, J = 8.0 Hz, 2H), 7.54 (d, J = 8.0 Hz, 2H),7.47 (t, J = 7.2, 2H), 7.37 (t, J = 7.2 Hz, 1H), 7.28 (d, J = 8.0 Hz, 2H), 2.44 (s, 3H) [ 55 ]; Product 3e (Biphenyl-4-carbaldehyde): 1 H NMR (400 MHz, CDCl 3 ): δ = 9.96 (s, 1H), 7.86 (d, J = 8.0 Hz, 2H), 7.66 (d, J = 8.0 Hz, 2H), 7.55 (d, J = 8.4 Hz, 2H), 7.40 (t, J = 7.2 Hz, 2H), 7.34 (t, J = 7.2 Hz, 1H) [ 55 ]; Product 3f (Biphenyl): 1 H NMR (400 MHz, CDCl 3 ): δ = 7.54 (d, J = 8.0 Hz, 4H), 7.39 (t, J = 8.0 Hz, 4H), 7.31–7.27 (m, 2H) [ 55 ]; Product 3g (4-Aminobiphenyl): 1 H NMR (400 MHz, CDCl 3 , TMS) δ 7.52 (d, J = 7.9 Hz, 2H, CH), 7.41–7.36 (m, 4H, CH), 7.25 (t, J = 7.3 Hz, 1H, CH), 6.73 (d, J = 8.5 Hz, 2H, CH), 3.68 (s, 2H) [ 57 ]; Product 3h (2-Cynobiphenyl): 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 7.76 (dd, J = 8.0Hz, 1.2Hz, 1H), 7.64 (td, J = 7.6 Hz, 1.2Hz, 1H), 7.58–7.54 (m, 2H), 7.54–7.40 (m, 5H) [ 58 ]; Product 4j (1,1′:4′,1″-terphenyl): 1 H NMR (400 MHz, Chloroform-d) δ 7.70 (s, 4H), 7.69–7.64 (m, 4H), 7.50–7.45 (m, 4H), 7.41–7.35 (m, 2H) ppm [ 43 ]; Product 5k (1,3,5-Triphenylbenzene): 1 H NMR (400 MHz, CDCl 3 ): δ = 7.71 (s, 3H), 7.63 (d, J = 7.2 Hz, 6H), 7.42 (t, J = 8.0 Hz, 6H), 7.31 (t, J = 6.8 Hz, 3H) [ 59 ].…”

Carbocation-Catalyzed Intramolecular and Intermolecular Carbonyl-Alkyne Metathesis Reactions

“…Based on our previous work on the promotion of the carbonyl-olefin metathesis reaction with the nonbenzenoid aromatic tropylium ion, we believed that tropylium should be a suitable organic Lewis acid catalyst for CAM processes as these two types of reactions share similar working principles. Apart from this, our group has also demonstrated tropylium’s catalytic efficiency in facilitating hydration of alkynes and reactions involving carbonyl compounds such as the acetalization reaction and retro-Claisen-type solvolysis and other synthetic applications . Herein, we report the application of tropylium tetrafluoborate, denoted as TropBF 4 , as an efficient organic Lewis acid promoter for both intramolecular and intermolecular carbonyl-alkyne metathesis with excellent outcomes.…”