Nanoparticulate Copper(II) Oxide Catalyzed Synthesis of Guanidine Derivatives and Their Conversion into Functionalized Iminoguanidines

Abstract

A simple synthesis of functionalized iminoguanidines from N-sulfoketenimines and N,N′,N′′-trisubstituted guanidines, generated by nanoparticulate copper(II) oxide-catalyzed hydroamination of di(cyclo)alkylcarbodiimides, is described.

Key words

imines - guanidines - ketenes - tandem reactions - azides - alkynes - carbodiimides

• References and Notes

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• 17 N-(Cyclo)alkyl-N-{[(cyclo)alkylamino](arylimino)methyl}-N′-(arylsulfonyl)hexanimidamides 7; General Procedure Aniline 1 (1 mmol), carbodiimide 2 (1.2 mmol), and nanoparticulate CuO (10 mol%) were stirred in toluene (2 mL) at 80 °C for 8 h. A mixture of sulfonyl azide 5, (1.2 mmol), alkyne 4 (1 mmol), CuI (0.019 g, 0.1 mmol), and Et₃N (0.101 g, 1 mmol) in toluene (2 mL) was slowly added, and the mixture was stirred at r.t. under N₂. When the reaction was complete [~4 h; TLC (EtOAc–hexane, 1:5)], the mixture was diluted with aq NH₄Cl (3 mL) and stirred for 30 min. The layers were separated and the aqueous layer was extracted with CH₂Cl₂ (3 × 3 mL). The organic fractions were combined, dried (Na₂SO₄), filtered, and concentrated under reduced pressure, and the residue was purified by flash column chromatography [silica gel (230–400 mesh; Merck), hexane–EtOAc (5:1)]. N-Cyclohexyl-N-[(cyclohexylamino)(phenylimino)methyl]-N′-(phenylsulfonyl)hexanimidamide (7a) Colorless crystals; yield: 0.45 g (84%); mp 134–137 °C. IR (KBr): 3329, 3053, 2930, 1652, 1590, 1513, 1448, 1343, 1266, 1146, 1092, 752 cm^–1. ¹H NMR (500 MHz, CDCl₃): δ = 0.98 (t, ³ J = 6.8 Hz, 3 H), 1.23–2.38 (m, 28 H), 3.27 (quint, ³ J = 6.8 Hz, 1 H), 3.62 (quint, ³ J = 6.8 Hz, 1 H), 6.73–6.83 (m, 3 H), 6.96 (s, 1 H), 7.18 (d, ³ J = 7.9 Hz, 2 H), 7.42–7.61 (m, 3 H), 7.88 (d, ³ J = 7.9 Hz, 2 H). ¹³C NMR (125.7 MHz, CDCl₃): δ = 13.6 (Me), 21.5 (CH₂), 22.3 (2 CH₂), 24.9 (CH₂), 25.5 (2 CH₂), 26.0 (CH₂), 29.1 (CH₂), 30.4 (CH₂), 31.0 (CH₂), 31.3 (CH₂), 32.6 (CH₂), 34.0 (CH₂), 43.6 (CH₂), 50.8 (CH), 57.8 (CH), 122.0 (3 CH), 125.1 (2 CH), 126.4 (2 CH), 128.5 (2 CH), 132.4 (CH), 143.2 (C), 144.7 (C), 154.8 (C), 155.5 (C). MS: m/z (%) = 536 (8) [M⁺], 478 (20), 395 (24), 362 (40), 238 (36), 141 (88), 91 (38), 77 (100). Anal. Calcd for C₃₁H₄₄N₄O₂S (536.77): C, 69.37; H, 8.26; N, 10.44. Found: C, 69.81; H, 8.32; N, 10.51.