参考路线如下：

(2-[(4-bromomethyl)phenyl]-5-(4-ethoxyphenyl)-1,3,4-oxadiazole) (3.40 g, 9.46 mmol) and triphenylphosphine (2.57 g, 9.80 mmol) were added to 45 mL dry benzene and the mixture was heated under reflux for 4 h. After cooling to room temperature, the reaction mixture was filtered to obtain the white solid phosphorane ylide and dried in vacuum (5.75 g, 9.26 mmol). Sodium hydride (0.32 g, 8.00 mmol) was put into 8 mL of petroleum ether under N2 atmosphere and stirred for 20 min. The petroleum ether was discarded and replaced with 30 mL dried CH2Cl2. Phosphorane ylide (4.13g, 6.65 mmol) was added and stirred at room temperature for 1 h. 5,5’-Diformyl-BAPTA-tetraethyl ester was synthesized from BAPTA-tetraethyl ester based on the literature methods.1,2 5,5’-Diformyl-BAPTA-tetraethyl ester (2.1 g, 3.26 mmol) was loaded into the mixture and stirred at room temperature for 6 h. The mixture was concentrated and purified by column chromatography using silica gel as the stationary phase and n-hexane/ethyl acetate (1:1) as the eluent to obtain the greenish yellow solid OBO-ester (2.1 g, 55.5 % yield).

OBO was obtained by hydrolysing OBO-ester in 0.50 M LiOH solution in an ice bath for 3 h. After hydrolysis, the pH was adjusted to 2–3 by dropwise addition of 1.0 M HCl with stirring. Yellow precipitate was collected by filtration and washed with 3 mL ice-water three times. Then the precipitate was put into 4 equivalents of LiOH solution again and stirred at 0 °C to gain the Li+ OBO salt. Finally, the purified Li+ OBO product was dried in vacuum and kept at -18 °C until further use.

• Identification

  Reaxys ID:	26686282
  Chemical Names:
  CAS Registry Number(s):		Substance type:
  Molecular Formula:	C58H48N6O14*4Li	Linear Structure Formula:	C58H48N6O14(4-)*4Li(1+)
  Molecular Weight:	1080.81	No of references:	1
  InChIKey:	WCYFMECOXKPLSC-UHFFFAOYSA-J