Intramolecular flexibility of heteroanalogous benzo- and dibenzo-1,5-cyclooctadienes

Neighboring Group Participation by Sulfonamido Nitrogen

“…A solution of N , N ′-ditosyl-1,2-diaminobenzene (25 g, 60.1 mmol) and cis -1,4-dichloro-2-butene (6.37 mL, 1.0 equiv) in acetonitrile (1500 mL) over K 2 CO 3 (41.6 g, 5.0 equiv) was heated to reflux for 24 h. At the end of that period, the reaction mixture was cooled down to room temperature, filtered, and freed of solvent under reduced pressure. The resulting pale yellow solid was purified over silica gel by flash chromatography using CH 2 Cl 2 /EtOAc (98:2) to provide 8 as a white powder (21.1 g, 75%), mp 215−216 °C (lit . mp 204 °C); 1 H NMR (CDCl 3 , 250 MHz) δ 7.67 (d, J = 8.4 Hz, 4H), 7.32−7.22 m, 8H), 5.61 (t, J = 4.0 Hz, 2H), 4.23 (d, J = 4.8 Hz, 4H), 2.44 (s, 6H).…”

Conformational study of the 4,9‐dihetero‐(Z,Z)‐cyclodeca‐1,6‐diene ring system; the mono‐ and di‐benzo analogues

“…The dynamic NMR parameters thus determined are given in Table 4 together with the free energies of activation, AG, #, at coalescence, estimated by using Eqn (1) and the Eyring Eqn (2). * kc=?,/-…”

Stereochemistry of benzannelated 1,6‐diazabicyclo[4.2.1]octadienes and the conformation of substituents on the methylene bridge

“…1,2,5,6-Tetrahydro-l,6-benzodiazocine (I, R = H) was prepared as described previ~usly.~ 1,6-Methano-l,2,S,6-tetrahydro-1,6-benzodiazocine (1). A mixture of I (R = H) (1.6 g; 0.01 mol), paraformaldehyde (1.2 g) and one drop of sulphuric acid in xylene (50 ml) was heated for 8 h while refluxing.…”