Scheme 12.

Attempted Synthesis of Oxepin 7 by Ring Expansion of a Diazo Epoxide^a

^aReagents and conditions. a) TrocN=NTroc (1.2 equiv), CH₂Cl₂, 41 °C, 4 h, 93%; b) TBAF (1.0 M in THF, 2.0 equiv), THF, 0 °C, 30 min, 92%; c) 1,1,1-trifluoro acetone (62 equiv), Na₂EDTA, NaHCO₃ aq. (15 equiv), oxone^(R) (38 equiv), MeCN, 0→25 °C, 15 h; d) Zn (21 equiv), MeOH/NH₄Cl aq. (1.0 M) (4:1), 25 °C, 2 h; then NH₄OH aq. (15 M), CuCl₂ aq. (1.0 M), 25 °C, 5 min, 76% for the two steps.