In a 300-mL two-necked round-bottomed flask
equipped with
a magnetic stirring bar and a rubber septum, NaOH (14.1 g, 353 mmol)
and H2O (50 mL) were added, respectively.12 (link) The reaction mixture was cooled to 0 °C and butane-1,4-diol
(9.01 g, 100 mmol) in THF (40 mL) and TsCl (41.9 g, 220 mmol) in THF
(100 mL) were added to this reaction mixture. The mixture was stirred
for 20 h at 0 °C. The pH was adjusted to 5–6 with 2 M
H2SO4 solution to quench the reaction. The mixture
was extracted with ethyl acetate (3 × 30 mL). The combined organic
phases were washed with H2O (3 × 30 mL), dried (with
Na2SO4), and concentrated in vacuo to give a
crude product, which was recrystallized from ethyl acetatete/methanol
(1:1) to give the titled compound 2a (29.9 g, 75%).