1.13 g of N,N′-(disulfanediyldiethane-2,1-diyl)bis(4-chlorobutanamide) was dispersed in 0.5 mL of N-methylpyrrolidinone and 2.5 mL acetonitrile and heated at 50° C. 0.71 mL of picoline was added and the reaction mixture was stirred for 5 days at 50° C. A few milligrams of cesium carbonate and additional 0.35 mL of 2-picoline were added. After one day at 65° C., the reaction mixture was poured in 50 mL acetonitrile. The resulting gum was washed several times with ethyl acetate, solubilized in ethanol, filtered and dried under vacuum. 0.95 g of a beige solid were obtained.
