Synlett 2011(3): 308-310  
DOI: 10.1055/s-0030-1259325
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of 2-Imino-3-aminobenzofurans via Multicomponent Reactions from TosMIC

Ma. Carmen García-Gonzáleza, Eduardo González-Zamora*a, Rosa Santillanb, Norberto Farfánc
a Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, San Rafael Atlixco 186, Col. Vicentina Iztapalapa, México D. F. 09340, México
Fax: +52(55)58044666; e-Mail: egz@xanum.uam.mx;
b Departamento de Química, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. Postal 14-740, México D. F. 07000, México
c Facultad de Química, Departamento de Química Orgánica, Universidad Nacional Autónoma de México, México D. F. 04510, México
Further Information

Publication History

Received 30 August 2010
Publication Date:
19 January 2011 (online)

Abstract

A simple synthesis of 2-imino-3-aminobenzofurans was developed based on multicomponent reactions from p-toluenesulfonylmethylisocyanide, salicylaldehyde, and substituted anilines. The crystal structures of two of the aminobenzofurans were established by X-ray crystal structure analysis.

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General Procedure for the Preparation of 2-Imino-3-aminobenzofurans
Salicylaldehyde 2 (2.00 mmol) was added to a solution of the amines 3a-f (1.00 mmol) in MeOH (15 mL). The mixture was stirred for 30 min at r.t. and p-toluenesulfonylmethyl isocyanide (4, 1.20 mmol) was added. The reaction mixture was refluxed (3-24 h), and the solid precipitate was collected by filtration and washed with hexane.
Selected Data for Compound 5a The product 5a (0.450 g) was obtained as a red solid in 61% yield, mp 253-255 ˚C. IR: 3366 (OH), 1595 (C=N), 1310, 1275, 744 cm. ¹H NMR (400 MHz, DMSO-d 6): δ = 11.52 (1 H, br s, OH), 10.78 (1 H, br s, OH), 8.98 (1 H, s, H-7), 8.44 (1 H, br s, NH), 7.71-7.67 (2 H, m, ArH), 7.60-7.56 (2 H, m, ArH), 7.42-7.32 (3 H, m, ArH), 7.24 (1 H, t, J = 7.6 Hz, ArH), 6.93-6.87 (2 H, m, ArH), 6.61 (1 H, d, J = 9.04 Hz, ArH). ¹³C NMR (100 MHz, DMSO-d 6): δ = 160.0, 156.2 (C=N), 151.0, 147.4, 144.8, 141.7, 138.4, 134.1, 132.1, 126.7, 126.4, 123.7, 120.7 (2 C), 120.1, 117.9, 117.2, 114.5, 111.9, 111.7, 109.2. MS (20 eV): m/z (%) = 389 (100) [M]+, 372 (16), 342 (8), 268 (27), 236 (13), 211 (25), 122 (38). HRMS: m/z calcd for C21H16N3O5 [M+ + H]+: 390.1084; found: 390.1083.

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Crystallographic data: Single crystal X-ray diffraction studies were realized on a KAPPA CCD diffractometer. Solution and refinement: direct methods SHELXS-86²0 and SIR-2004²¹ for structure solution and the SHELXL-97²² software package for refinement and data output. For compounds 5a and 5c full crystallographic data were submitted as CIF files with the Cambridge Crystallographic Data Centre, CCDC Nos. 750840 for 5a and 750841 for 5c.