Different pathways in the reaction of N-(tosylmethyl)-substituted ureas, thioureas, and N′-cyanoguanidines with sodium cyanide. Synthesis of α-ureido nitriles, α-ureido amides, and hydantoin imino derivatives

A new synthesis of 3-arylideneamino- and 3-alkylideneamino-substituted hydantoins

“…Previously, we demonstrated that treatment of α-ureidonitriles with conc. HCl at room temperature gives the corresponding amides in high yields [38]. In contrast, the reaction of nitrile 2a with conc.…”

“…Recently, we have shown that N-(tosylmethyl)-substituted ureas smoothly react with sodium cyanide in aprotic solvents to give the corresponding nitriles of α-ureidocarboxylic acids [38]. However, in the case of 4-(tosylmethyl)semicarbazones, the outcome of the cyanation is not obvious due to significant structural differences between ureido and semicarbazono groups.…”

“…However, in contrast to the reaction of N-(tosylmethyl)ureas with NaCN [38], the outcome of the reaction of sulfone 1a with NaCN is extremely sensitive to reaction conditions (Table 1). Using DMF as a solvent, an increase in temperature (entry 1 vs. entry 2), reaction time (entry 3 vs. entry 4), and excess of NaCN (entry 2 vs. entry 3) lead to a significant increase in the number and amount of side products.…”

“…A significantly higher ability of nitrile 2a to cyclize under basic conditions compared with nitriles of α-ureidocarboxylic acids [38] can be explained by increased NH acidity of semicarbazones. Deprotonation of the N(2)H in 2a with NaCN gives the corresponding conjugated base followed by its cyclization into imine 5a which tautomerizes into enamine 4a.…”