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

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.

multicomponent reactions - imines - furans - TosMIC - isocyanide

References and Notes

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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^-¹. ^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-86^²0 and SIR-2004^²¹ for structure solution and the SHELXL-97^²² 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.

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