General procedure: The synthesis was carried out using the general procedure 2 and the product was purified by recrystallization in methanol. Yield analysis showed that the yield was 35% in open vessel in standard temperature control mode and 13% in power/time mode and 54% in closed vessel in standard temperature control mode and 60% in power/time mode. The product obtained was white crystal with a melting point of 148-150°C (literature value [2]: 150-152°C). Infrared spectra (KBr pressed sheet, cm^-1) showed characteristic absorption peaks located at 1040-1120 (-C-O-). NMR hydrogen spectrum (400MHz, CDCl3, ppm): 2.26 (quadruple peak, 4H, J=5.6Hz, -CH2-), 4.24 (triple peak, 8H, J=5.6Hz, -CH2-), 6.89-6.91 (multiple peaks, 8H, aromatic hydrogen). NMR carbon spectra (100 MHz, CDCl3, ppm): 29.28, 67.32, 115.58, 121.72, 149.44. Calculated values for elemental analysis (C18H20O4): C, 71.98; H, 6.71; O, 21.31; measured values: C, 72.39; H, 6.25; O, 21.36. Similarly, the can be synthesized by a two-step microwave-assisted synthesis, but requires the use of a diphenol intermediate instead of catechol as a precursor. Depending on the alkyl dihalides used in the ring-closing reaction, the method allows the preparation of symmetrical or asymmetrical dibenzocrown ethers (2-6).
