Highly efficient methods for metacyclophane synthesis

Highly efficient methods for synthesizing metacyclophanes such as 2,6-bridged pyrones and pyridines are described. 4-Hydroxy-2-pyrone derivative bridged at the 3 and 6-positions is readily available. This compound was transformed into 2,6-bridged 4-pyrone on heating in ethanol or in hydrochloric acid. Heating with ammonia or methylamine afforded the corresponding 2,6-bridged 4-pyrone or . These pyridones were synthesized directly from by treatment with ammonia or methylamine. These methods have a wide applicability to the bridge length of metacyclophane; compounds with a short bridge (n=8) as well as long bridge (n=18) are synthesized in satisfactory yields.