Synthesis of cycloheptanes from 1,6-diols^a.

^aReaction conditions: 1 (7 mol%, with respect to 2a), 2a (0.5 mmol), substituted-1,6-hexanediol (1.5 mmol), KO^tBu (1 mmol), toluene (5 mL), 135 °C, 24 h (isolated yield).