PDF herunterladen
Synlett 2010(10): 1469-1472  
DOI: 10.1055/s-0029-1219934
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

An Unprecedented and Concise Method for the Synthesis of 1,3-Thiazino-[3,4a][1,3]benzimidazoles via a Three-Component Reaction

Abdolali Alizadeh*, Zohreh Noaparast, Hamideh Sabahnoo, Nasrin Zohreh
Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, 1411713116 Tehran, Iran
Fax: +98(21)88006544; e-Mail: abdol_alizad@yahoo.com; e-Mail: aalizadeh@modares.ac.ir;
Weitere Informationen

Publikationsverlauf

Received 15 February 2010
Publikationsdatum:
10. Mai 2010 (online)

    Lizenzen und Reprints Alle Artikel dieser Rubrik

Abstract

For the first time, a novel, simple, and highly efficient synthesis of N-aryl-N-[1,3]thiazino[3,4a][1,3]benzimidazol-1-ylidenamines is presented. The one-pot reaction of o-phenylenediamine, aryl isothiocyanate, and methyl acetylenecarboxylate proceeds in toluene-dichloromethane without any catalyst under reflux conditions to produce the title compounds in 60-70% yield. From a mechanistic point of view, the reaction is proposed to occur via two cyclizations and four heteroatom-carbon bond formations.

Key words

benzimidazole - 1,3-thiazine - thiazinobenzimidazole - methyl propiolate - o-phenylenediamine - aryl isothiocyanate - multicomponent reaction

20

To a magnetically stirred 5 mL flask containing o-pheny-lenediamine (0.11 g, 1 mmol) and CH2Cl2 (2 mL as solvent) was added phenyl isothiocyanate (0.14 g, 1 mmol). After 15 min, methyl acetylenedicarboxylate (0.08 g, 1 mmol) in toluene (5 mL) was added to the reaction mixture and stirring continued under reflux. After completion of the reaction (ca. 10 h; monitoring by TLC based on the presence of intermediate 5), the solvent was removed under reduced pressure, and the residue was washed with cold toluene, Et2O, and EtOAc and crystallized from CH2Cl2.
Compound 4a: yield 0.19 g (70%); white powder; mp 220 ˚C (dec.). IR (KBr): 1685 (C=N), 1663 (C=N), 1638 (C=C), 1589 and 1527 and 1473 and (C=C Ar). ¹H NMR (500.13 MHz, CDCl3): δH = 6.32 (1 H, d, ³ J H,H = 7.7 Hz, SCHCH), 7.31 (1 H, t, ³ J H,H = 7.5, CH of Ar), 7.35 (1 H, t, ³ J H,H = 7.2 Hz, CH of Ar), 7.44 (2 H, d, ³ J H,H = 7.6 Hz, 2 CH of Ar), 7.52 (1 H, t, ³ J H,H = 7.4 Hz, CH of Ar), 7.55 (1 H, d, ³ J H,H = 7.8 Hz, CH of Ar), 7.60 (2 H, t, ³ J H,H = 7.5 Hz, 2 CH of Ar), 7.66 (1 H, d, ³ J H,H = 7.9 Hz, CH of Ar), 8.17 (1 H, d, ³ J H,H = 7.7 Hz, SCHCH). ¹³C NMR (125.75 MHz, CDCl3): δC = 106.01 (SCH=CH), 108.49 (CH of Ar), 119.62 (CH of Ar), 122.18 (CH of Ar), 124.90 (CH of Ar), 128.22 (2 CH of Ar), 129.17 (C ipso of Ar), 129.47 (CH of Ar), 129.86 (2 CH of Ar), 132.52 (SCHCH), 134.74 (CH=CHC), 142.41 (C ipso of Ar), 148 (C ipso of Ar), 160.38 (N=CS). MS: m/z (%) = 279 (7) [M+ + 2], 277 (6) [M+], 260 (100), 250 (10), 207 (9), 185 (9), 167 (18), 149 (49), 130 (16), 118 (9), 105 (92), 91 (55), 77 (90), 57 (48). 43 (53). Anal. Calcd for C16H11N3S (277.34): C, 69.29; H, 4; N, 15.15. Found: C, 69.32; H, 4.2; N, 15.13.
Compunds 4e and 4e′: yield 0.20 g (67%); white powder; mp 230 ˚C (dec.). IR (KBr): 1676 (2 C=N), 1635 (2 C=N), 1591 (2 C=C), 1533 and 1509 and 1464 and (Ar). ¹H NMR (500.13 MHz, CDCl3): δH = 2.43 (6 H, s, 2 Me), 2.45 (3 H, s, Me), 2.51 (3 H, s, Me), 6.27 (1 H, d, ³ J H,H = 7.7, SCHCH), 6.28 (1 H, d, ³ J H,H = 7.8 Hz, SCHCH), 7.11 (1 H, d, ³ J H,H = 7.9 Hz, CH of Ar), 7.15 (1 H, d,³ J H,H = 8.2 Hz, CH of Ar), 7.32 (4 H, d, ³ J H,H = 7.3, 4 CH of Ar), 7.34 (1 H, s, CH of Ar), 7.38 (4 H, d,³ J H,H = 8.1 Hz, 4 CH of Ar), 7.41 (1 H, d, ³ J H,H = 8.2 Hz, CH of Ar), 7.45 (1 H, s, CH of Ar), 7.54 (1 H, d, ³ J H,H = 8.2 Hz, CH of Ar), 8.11 (1 H, d, ³ J H,H = 7.7Hz, SCHCH), 8.12 (1 H, d, ³ J H,H = 7.8 Hz, SCHCH). ¹³C NMR (125.7 MHz, CDCl3): δC = 21.37 (2 Me), 21.71 (Me), 21.75 (Me), 105.62, and 105.79 (2 SCH=CH), 108.01 and 108.59 (2 CH of Ar), 119.17 and 119.65 (2 CH of Ar), 123.28 (2 CH of Ar), 126.14 (2 CH of Ar), 127.20 (C ipso of Ar), 127.87 (2 CH of Ar), 128.90 (C ipso of Ar), 129.30 (C ipso of Ar), 130.10 (C ipso of Ar), 130.60 (2 CH of Ar), 132.16 and 132.23 (2 CH of Ar), 132.40 and 132.53 (2 SCHCH), 134.83 (2 CH=CHC), 139.43 (2 C ipso of Ar), 140.37 and 142.41 (2 C ipso of Ar), 148.04 (2 C ipso of Ar), 160.38 (2 N=CS). MS: m/z (%) = 290 (22), 289 (100), 274 (6), 260 (10), 246 (6), 224 (4), 208 (2), 167 (16), 149 (42), 129 (5), 111 (7), 97 (13), 83 (15), 57 (23), 43 (17). Anal. Calcd for C18H15N3S (305. 40): C, 70.79; H, 4.95; N, 13.76. Found: C, 70.77; H, 4.97; N, 13.74.