Chlorinated Polycyclic Compounds. VI. Alkaline Cleavage of Chloro-substituted Dibenzobicyclo[3.2.1]octadien-4-ones.

Model Studies Directed toward the Total Synthesis of (±)-Ribasine. A Tandem Cyclization−Cycloaddition Route Leading to the Core Skeleton

“…A solution containing 0.06 g (0.2 mmol) of cyclobutanone 44 in 100 mL of CH 2 Cl 2 at 25 °C was irradiated with a 450-W Hanovia lamp equipped with a Pyrex glass filter sleeve for 3 h under argon. The solvent was removed under reduced pressure, and the residue was subjected to silica gel chromatography to give the known indene 45 as a clear oil in 78% yield: IR (neat) 1713, 1598, 1288, and 1128 cm -1 ; 1 H NMR (300 MHz, CDCl 3 ) δ 0.82 (t, 3H, J = 7.0 Hz), 3.52 (d, 2H, J = 1.9 Hz), 3.96 (q, 2H, J = 7.0 Hz), 6.46 (t, 1H, J = 1.9 Hz), 7.07 (m, 1H), 7.20 (m, 2H), 7.50 (m, 4H), and 7.95 (dd, 1H, J = 7.5 and 1.5 Hz); 13 C NMR (75 MHz, CDCl 3 ) δ 13.2, 38.1, 60.8, 119.5, 123.7, 124.5, 126.0, 127.5, 130.0, 130.2, 130.6, 130.9, 131.7, 136.4, 143.2, 145.2, 145.5, and 168.0.…”