Dinuclear Titanium Complexes with Sulfamide Ligands as Precatalysts for Hydroaminoalkylation and Hydroamination Reactions

Abstract

A new dinuclear titanium sulfamide complex was synthesized from N,N′-diphenylsulfamide and Ti(NMe₂)₄ and used as a precatalyst for the intermolecular hydroaminoalkylation of alkenes as well as the intramolecular hydroamination of alkenes.

Key words

alkenes - amines - homogeneous catalysis - sulfur - titanium

• References and Notes

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• 14 Experimental Procedure N,N′-Diphenylsulfamide (1, 0.248 g, 1.0 mmol) was slowly added to a solution of Ti(NMe₂)₄ (0.224 g, 1.0 mmol) in toluene (5 mL) at r.t. The reaction mixture was stirred for 3 h, and then the solvent was removed under vacuum. The resulting solid was recrystallized from a mixture of toluene and CH₂Cl₂ (10:3) to give red crystals of complex 2 (0.311 g, 81%). ¹H NMR (500 MHz, CDCl₃): δ = 3.31 (s, 24 H, CH₃), 6.96 (d, ³ J _H,H = 8.0 Hz, 8 H, PhH _ortho ), 7.01 (t, ³ J _H,H = 7.3 Hz, 4 H, PhH _para ), 7.14 (t, ³ J _H,H = 7.7 Hz, 8 H, PhH _meta ) ppm. ¹³C NMR (126 MHz, C₆D₆): δ = 47.7 (CH₃), 124.5 (CH), 125.6 (CH), 128.6 (CH), 143.1 (C) ppm.
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• 15b Royo E, Betancort JM, Davis TJ, Carroll P, Walsh PJ. Organometallics 2000; 19: 4840
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• 16 Compound 2: red crystals (polyhedron), dimensions 0.50 × 0.21 × 0.15 mm³, monoclinic, space group P2₁/n, unit cell dimensions: a = 9.0358(2) Å, b = 16.0367(3) Å, c = 12.5598(2) Å, α = 90°, β = 96.6210(10)°, γ = 90°, V = 1807.83(6) ų, Z = 2, ρ = 1.410 Mg/m³, Θ_max= 34.99°, radiation Mo Kα, λ = 0.71073 Å, φ and ω scans with Bruker KAPPA APEX-II CCD at T = 153(2) K, 32381 reflections measured, 7876 unique [R _int = 0.0470], 6067 observed [I > 2σ(I)], intensities were corrected for Lorentz and polarization effects, an empirical absorption correction was applied using Bruker SAINT based on the Laue symmetry of the reciprocal space, μ = 0.611 mm^–1, T_min = 0.7516, T_max = 0.9150, structure solved by direct methods and refined against F ² with a full-matrix least-squares algorithm using the SHELXS-97 software package, 230 parameters refined, hydrogen atoms were treated using appropriate riding models, goodness of fit 1.026 for observed reflections, final residual values R ₁ = 0.0341, wR ₂ = 0.0901 for observed reflections, largest diff. peak, hole 0.456 and –0.327 eÅ^–3. The structure contains about 4% Cl atoms in the para position of the phenyl substituents. This is caused by a chlorination side reaction that takes place during the synthesis of the ligand 1. However, the impurity could not be observed by ¹H NMR. CCDC number 883164 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
• 17 Experimental Procedure N,N′-Diphenylsulfamide (1, 0.612 g, 2.5 mmol) was slowly added to a solution of Ti(NMe₂)₄ (1.14 g, 5.1 mmol) in n-hexane (10 mL) at r.t. The reaction mixture was stirred for 3 h, and then the dispersed precipitate was filtered off quickly. The resulting solid was dried under vacuum to give the pure complex 3 (0.990 g, 65%) as a light yellow powder. For crystallization, a concentrated solution of 3 in a mixture of n-hexane and toluene (5:3) was stored at 4 °C to give light yellow crystals. ¹H NMR (500 MHz, C₆D₆): δ = 3.13 (s, 36 H, CH₃), 6.94 (t, ³ J _H,H = 7.3 Hz, 2 H, PhH _para ), 7.12–7.17 (m, 4 H, PhH _meta ), 7.28 (d, ³ J _H,H = 8.1 Hz, 4 H, PhH _ortho ) ppm. ¹³C NMR (126 MHz, C₆D₆): δ = 46.4 (CH₃), 124.4 (CH), 125.2 (CH), 129.2 (CH), 144.0 (C) ppm.
• 18 Compound 3: light yellow crystals (polyhedron), dimensions 0.60 × 0.48 × 0.33 mm³, monoclinic, space group P2₁/n, unit cell dimensions: a = 8.9022(2) Å, b = 24.2017(7) Å, c = 14.9008(4) Å, α = 90°, β = 94.0400(10)°, γ = 90°, V = 3202.38(15) ų, Z = 4, ρ = 1.258 Mg/m³, Θ_max = 35.07°, radiation Mo Kα, λ = 0.71073 Å, φ and ω scans with Bruker KAPPA APEX-II CCD at T = 153(2) K, 71359 reflections measured, 13938 unique [R _int = 0.0694], 10557 observed [I > 2σ(I)], intensities were corrected for Lorentz and polarization effects, an empirical absorption correction was applied using Bruker SAINT based on the Laue symmetry of the reciprocal space, μ = 0.597 mm^–1, T _min = 0.716, T _max = 0.821, structure solved by direct methods and refined against F ² with a full-matrix least-squares algorithm using the SHELXS-97 software package, 346 parameters refined, hydrogen atoms were treated using appropriate riding models, goodness of fit 1.045 for observed reflections, final residual values R ₁ = 0.0419, wR ₂ = 0.1073 for observed reflections, largest diff. peak, hole 0.778 and –0.382 eÅ^–3. CCDC number 883163 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
• 19 General Procedure Exemplified by the Reaction of 1-Octene with N-Methylaniline An oven-dried Schlenk tube equipped with a Teflon stopcock, and a magnetic stirring bar was transferred to a nitrogen-filled glove box and charged with the catalyst 3 (61 mg, 0.1 mmol, 5 mol%), n-hexane (1 mL), 1-octene (337 mg, 3.0 mmol), and N-methylaniline (214 mg, 2.0 mmol). The tube was sealed, and the resulting mixture was heated to 120 °C for 48 h. The crude product was purified by flash chromatography (PE–EtOAc = 40:1) to give a mixture of the regioisomers 4a and 4b (336 mg, 1.53 mmol, 77%, 97:3) as a colorless oil. All compounds were identified by com-parison of the obtained ¹H NMR and ¹³C NMR spectra with those reported in the literature.^3–5