Table 2.

A variety of densely substituted products were obtained using a stepwise cyclization/demetallation approach, sorted by demetallation. X-ray structure of 10c. (a) 1-Fluoro-2,6-dichloropyridinium tetrafluoroborate (2 equiv), THF, 0 °C to 25 °C. (b) TMSCl, 3:1 THF:D₂O, 0 °C to 25 °C. (c) TMSCl, THF, −20 °C to 25 °C then K₂CO₃ (d) TMSCl, THF, 25 °C then H₂O (e) N-Bromosuccinimide (1.0 equiv), THF, 0 °C, 30 min then 25 °C. (f) I₂ (1.5 equiv), THF, 0 °C to 25 °C, in dark. (g) N-Chlorosuccinimide (1.5 equiv), THF, 0 °C to 25 °C. (h) Br₂ (3.5 equiv), THF, 0 °C to 25 °C, 12 h, then Bu₄NBr (3 equiv), CH₂Cl₂, 40 °C, 6 h. (i) N-Bromosuccinimide (3.0 equiv), THF, 0 °C, 30 min then 25 °C. (j) N-Iodoosuccinimide (3.0 equiv), THF, 0 °C, 30 min then 25 °C. (k) Cerium ammonium nitrate (1.5 equiv), 1:1 MeOH:THF, K₂CO₃ (powdered, 10 equiv.), CO balloon.