The Reaction of Carbanilides with Sodium Hypochlorite¹

Product Class 4: Benzimidazoles

“…[291] Similarly, N-aryl-N¢-methoxyureas have been converted by tert-butyl hypochlorite, in a one-pot reaction, initially into unstable N-aryl-N¢-chloro-N¢-methoxyureas, which cyclize in basic conditions to give 1-methoxybenzimidazol-2-ones 83 (R 1 = OMe) in 56±83% yields. For example, 6-chloro-1-phenyl-1H-benzimidazol-2(3H)-one (83, R 1 = Ph; X = 6-Cl) has been prepared in 57% yield in this way from N-(4-chlorophenyl)-N¢-phenylurea.…”

“…For example, 6-chloro-1-phenyl-1H-benzimidazol-2(3H)-one (83, R 1 = Ph; X = 6-Cl) has been prepared in 57% yield in this way from N-(4-chlorophenyl)-N¢-phenylurea. [291] Scheme 42 Cyclization of an Arylurea [291,292] 1-Methoxy-1H-benzimidazol-2(3H)-one (83, R 1 = OMe; X = H); Typical Procedure from 1-Aryl-3-methoxyureas: [292] To a soln of N-methoxy-N¢-phenylurea (82, R 1 = OMe; X = H; 33.2 g, 0.22 mol) in CH 2 Cl 2 (400 mL) at ±30 8C was added slowly over 20 min tert-butyl hypochlorite (24 mL). [292] It is not possible to cyclize the diarylureas if one or both of the nitrogens are alkylated, or if each of the aryl rings contains two or more electron-attracting substituents.…”

“…6-Chloro-1-phenyl-1H-benzimidazol-2(3H)-one (83, R 1 = Ph; X = 6-Cl): [291] To a slurry of the carbanilide 82 (R 1 = Ph; X = 4-Cl; 10.6 g, 43 mmol) in MeOH (300 mL) was added a soln of NaOH (4 g) in H 2 O (15 mL). After cooling in an ice±water bath, the mixture was treated with 1.36 M NaOCl (110 mL, 150 mmol), keeping the temperature below 35 8C.…”

Pd(II)/Ag(I)-Promoted One-Pot Synthesis of Cyclic Ureas from (Hetero)Aromatic Amines and Isocyanates

“…Due to its inefficiency, the use of toxic reagents, and limited availability of diversely substituted 1,2-diamino­benzenes, alternative protocols such as transition-metal-catalyzed inter- (path b) or intramolecular (path c) C–N bond formation using ortho -haloaniline derivatives have been developed. Obviously, a direct C–H amidation of N , N ′-disubstituted ureas would be a more efficient route toward this scaffold, obviating the need for prehalogenation (path d): A handful of experimental studies under metal-free conditions have been reported …”