6,6-BIS(4-CARBOXY-2-OXABUTYL)-4,8-DIOXAUNDECANE-1, 11-DICARBOXYLIC ACID synthesis

Yield: 95%

Reaction Conditions:

with hydrogenchloride;water at 80; for 3 h;

Steps:

2.2 6,6-Bis(4-carboxy-2-oxabutyl)-4,8-dioxaundecane-1,11-dicarboxylic acid (3)
The mixture of 5,5-bis(4-cyano-2-oxabutyl)-1,9-dicyano-3,7-dioxanonane 2 (50 g, 143.5 mmol) and 36% hydrochloric acid (130 mL) was stirred and heated to 80 °C in an oil bath.
After 30 min white solid starts to precipitate, and after 3 h of heating the reaction mixture was cooled initially in cold water, and then in a refrigerator (-20 °C).
The precipitate of NH₄Cl was filtered and washed with acetone (2*50 mL).
The filtrate was evaporated in vacuum to give a mixture of solid and oily compounds.
A portion of acetone (200 mL) was added to dissolve crude tetracarboxylic acid 5, and white precipitate (the residual NH₄Cl) was removed by filtration.
The filtrate was evaporated in vacuum to give crude 5 which was recrystallized from dry acetonitrile (70 mL).
After removing of the obtained crystals the filtrate was evaporated and the residue was repeatedly recrystallized from acetonitrile.
(The product crystallizes from acetonitrile very slowly therefore the solution was left at -20 °C overnight.) Two portions of solid products were combined to one and desiccation of it in vacuum of oil pump afforded product as white crystals (58.0 g; 137 mmol; 95% yield), mp 99-101 °C (MeCN), lit.
^13a
mp 104-106 °C, lit.
^13b
mp 107-109 °C. ¹H NMR (500 MHz; DMSO-d₆) δ 12.08 (br s, 4H), 3.53 (t, 8H; J 6.3 Hz), 3.24 (s, 8H), 2.4 (t, 8H, J 6.3 Hz); ¹³C NMR (500 MHz; DMSO-d₆) δ 172.63, 69.03, 66.75, 45.10, 34.68.

References:

Ponomarenko, Anna I.;Brylev, Vladimir A.;Sapozhnikova, Ksenia A.;Ustinov, Alexey V.;Prokhorenko, Igor A.;Zatsepin, Timofei S.;Korshun, Vladimir A. [Tetrahedron,2016,vol. 72,# 19,p. 2386 - 2391]