A Novel Synthesis of Highly Functionalized 1,2,4-Diselenazolidines from Acyl Isoselenocyanates

Abstract

A simple one-pot synthesis of highly functionalized 1,2,4-diselenazolidines is described. Treatment of an acyl chloride with potassium selenocyanate in acetone gave an acyl isoselenocyanate and propane-2-selone, which both reacted with benzylamine or its derivatives to give the required products.

Keywords

diselenazolidines - acyl isoselenocyanates - tandem reactions - heterocycles - selones - benzylamines

• References and Notes

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• 17 1,2,4-Diselenazolidines 5; General Procedure A solution of the acyl chloride 1 (1 mmol) in acetone (2 mL) was slowly added to a solution of KSeCN (0.144 g, 2 mmol) in acetone (2 mL), and the mixture was stirred at r.t. for 30 min. A mixture of benzylamine 4 (1 mmol) and acetone (2 mL) was added and the mixture was stirred at r.t. for 10 h. When the reaction was complete [TLC (EtOAc–hexane, 1:5)], the mixture was extracted with CH₂Cl₂, and the extracts were washed with H₂O. The organic layers were combined, dried (Na₂SO₄), filtered, and concentrated under reduced pressure. The residue was purified by flash column chromatography [silica gel (230–400 mesh; Merck), EtOAc–hexane (1:5)]. N-(4-Benzyl-5,5-dimethyl-1,2,4-diselenazolidin-3-ylidene)benzamide (5a) Yellow powder; yield: 0.34 g (78%); mp 116–118 °C. IR (KBr): 1557, 1486, 1367, 1281, 1169 cm^–1. ¹H NMR (500 MHz, CDCl₃): δ = 1.97 (s, 6 H, 2 Me), 5.19 (s, 2 H, CH₂), 7.33 (t, ³J = 7.1 Hz, 1 H, CH), 7.37–7.44 (m, 6 H, 6 CH), 7.53 (t, ³J = 7.6 Hz, 1 H, CH), 8.20 (d, ³J = 7.6 Hz, 2 H, 2 CH). ¹³C NMR (125.7 MHz, CDCl₃): δ = 29.6 (2 Me), 52.4 (CH₂), 69.0 (C), 127.4 (2 CH), 128.0 (CH), 128.6 (2 CH), 129.2 (2 CH), 130.1 (2 CH), 132.9 (CH), 135.4 (C), 137.8 (C), 173.9 (C), 177.1 (C); MS: m/z (%) = 438 (8) [M⁺], 361 (20), 347 (36), 333 (39), 105 (68), 91 (85), 77 (100). Anal. Calcd for C₁₈H₁₈N₂OSe₂ (436.27): C, 49.55; H, 4.16; N, 6.42. Found: C, 49.73; H, 4.14; N, 6.48. X-Ray Crystal-Structure Determination of 5a: Structure determination and refinement data: formula, C₁₈H₁₈N₂OSe₂: M_r 436.26; Monoclinic, space group P21/n, a = 20.007(2), b = 9.678(1), c = 20.165(2) Å; β= 112.80(1), Z = 8, V = 3599.4(6) ų, D_calcd = 1.610 Mg/m³, Mo Kα radiation (0.71073 Å), T = 293(2) K; 7262 reflections collected on a Bruker P4 diffractometer, 6254 unique (R_int = 0.0481), 2929 unique reflections with I > 2σ(I). The structure was solved by direct methods and refined by full-matrix least-squares techniques using the SHELXL-97 package. There are two molecules in the asymmetric unit. All nonhydrogen atoms were refined anisotropically. The hydrogen atoms were placed on calculated positions and refined isotropically by using the riding model. Final indices [I > 2σ(I)]: R₁ = 0.0635, wR₂ = 0.1045, GoF = 0.993. CCDC 1470475 contains the supplementary crystallographic data for this paper. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/getstructures.
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