Phosphine-Catalyzed Synthesis of Unsymmetrical 1,3-Bis- and Trisphosphorus Ligands

Abstract

Phosphine-catalyzed umpolung γ-additions of phosphorus pronucleophiles on alkynes bearing phosphinoyl (P=O) or phosphinothioyl (P=S) moieties have been explored. The reaction leads to bis- or trisphosphorus subunits that can be useful for the preparation of chelating ligands.

Key words

addition reactions - catalysis - umpolung - chelates - phosphorus

References and Notes

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9

General Procedure for the Preparation of Compounds 1
To a soln of phosphoric chloride (5.5 mmol) in dry THF propynylmagnesium bromide (10 mL, 5 mmol, 0.5 M in THF) was added dropwise under Ar at -78 ˚C. The mixture was stirred at this temperature for 2 h, diluted with Et₂O, washed with a sat. soln of NH₄Cl and brine, dried over MgSO₄, filtered, and concentrated under vacuum. The crude residue was purified by column chromatography on SiO₂ (eluent: EtOAc-cyclohexane = 8:2).
Compound 1a: white solid, mp 89-90 ˚C. ^¹H NMR (400 MHz, CDCl₃): δ = 2.11 (d, J = 3.6 Hz, 3 H), 7.43-7.48 (m, 6 H), 7.79-7.85 (m, 4 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 5.02 (d, J = 3 Hz), 75.33 (d, J = 174 Hz), 105.46 (d, J = 32 Hz), 128.44 (t, J = 10 Hz), 130.81 (d, J = 12 Hz), 132.01 (d, J = 3 Hz), 133.20 (d, J = 121 Hz) ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 7.76 ppm. MS (ESI/TOF): m/z = 241 [M + H]⁺.
Compound 1b: white solid, mp 67-68 ˚C. ^¹H NMR (400 MHz, CDCl₃): δ = 1.86 (d, J = 14.4 Hz, 3 H), 2.04 (d, J = 3.6 Hz, 3H), 7.47-7.56 (m, 3H), 7.81-7.87 (m, 2H).^¹³C NMR (100 MHz, CDCl₃): δ = 4.77 (d, J = 3 Hz), 20.53 (d, J = 86 Hz), 75.22 (d, J = 167 Hz), 103.2 (d, J = 32 Hz), 128.56 (d, J = 13 Hz), 129.85 (d, J = 11 Hz), 131.99 (d, J = 3 Hz), 133.54 (d, J = 118 Hz) ppm. ^³¹P NMR (160 MHz, CDCl₃) δ = 10.17 ppm. MS (ESI/TOF): m/z = 179 [M + H]⁺. Compound 1c: white solid, mp 93-94 ˚C. ^¹H NMR (400 MHz, CDCl₃): δ = 2.12 (d, J = 4 Hz, 3 H), 7.41-7.48 (m, 6 H), 7.89-7.92 (m, 4 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 5.39 (d, J = 3 Hz), 73.25 (d, J = 158 Hz), 106.07 (d, J = 28 Hz), 128.52 (d, J = 14 Hz), 130.73 (d, J = 12 Hz), 131.66 (d, J = 3 Hz), 133.83 (d, J = 97 Hz) ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 19.69 ppm. MS (ESI/TOF): m/z = 257 [M + H]⁺.
Compound 1d: white solid, mp 85-86 ˚C. ^¹H NMR (400 MHz, CDCl₃): δ = 1.88 (d, J = 4.0 Hz, 6 H), 7.31-7.41 (m, 3 H), 7.77 (dd, J = 7.2, 15.6 Hz) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 4.76 (d, J = 4 Hz), 74.85 (d, J = 102 Hz), 103.42 (d, J = 39 Hz), 128.47 (d, J = 15 Hz), 129.92 (d, J = 12 Hz), 132.35 (d, J = 3 Hz), 132.97 (d, J = 141 Hz) ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = -20.76 ppm. MS (ESI/TOF):
m/z = 203 [M + H]⁺.
General Procedure for γ-P-Addition Reaction
The mixture of compound 1 (1 equiv), phosphorus pronucleophiles (1.2 equiv), and tributylphosphine (0.2 equiv) in 2-PrOH was irradiated under microwave for 30 min at 150 ˚C. The solvent was evaporated under vacuum, and the product was purified by column chromatography on SiO₂ (eluent: acetone).
Compound 2a: white solid, mp 87-90 ˚C. ^¹H NMR (400 MHz, CDCl₃): δ = 3.36 (dd, J = 7.6 Hz, J = 15.2 Hz, 2 H), 6.34-6.46 (m, 1 H), 6.47-6.60 (m, 1 H), 7.33-7.56 (m, 16 H), 7.69-7.75 (m, 4 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 36.61 (d, J = 17 Hz), 37.25 (d, J = 17 Hz), 128.45 (d, J = 12 Hz), 128.76 (d, J = 12 Hz), 129.44 (d, J = 10 Hz), 130.86 (d, J = 10 Hz), 131.25 (d, J = 10 Hz), 131.76 (d, J = 3 Hz), 131.61, 132.12 (d, J = 2 Hz), 132.19, 132.66, 140.17-140.30 (m)ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 23.38, 23.42, 28.96, 29.00 ppm. MS (ESI/TOF): m/z = 443 [M + H]⁺.
General Procedure for Hydrogenation of Compounds 2 and 3
A mixture of 2 and 3 was hydrogenated using Pd/C (0.03 equiv of 10% Pd/C) catalyst in EtOH at r.t. for 24 h. After filtration, the residue was washed with EtOH (3×). The combined organic phases were evaporated to give desired product.
Compound 4a: white solid, mp 142-144 ˚C. ^¹H NMR (400 MHz, CDCl₃): δ = 1.91-2.02 (m, 2 H), 2.43-2.50 (m, 4 H), 7.35-7.46 (m, 12 H), 7.63-7.66 (m, 8 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 14.85, 29.95 (dd, J = 11, 71 Hz), 128.59 (d, J = 12 Hz), 130.61 (d, J = 9 Hz), 131.68 (d, J =
3 Hz), 132.53 (d, J = 98 Hz) ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 32.52 ppm. MS (ESI/TOF): m/z = 445 [M + H]⁺. HRMS: m/z calcd for C₂₇H₂₆O₂NaP₂: 467.1306; found: 467.1312.
Compound 4b: yellow oil. ^¹H NMR (400 MHz, CDCl₃): δ = 1.23 (t, J = 7.2 Hz, 6 H), 1.81-1.95 (m, 4 H), 2.38-2.43 (m, 2 H), 3.98-4.03 (m, 4 H), 7.43-7.51 (m, 6 H), 7.69-7.75 (m, 4 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 15.29, 16.33 (d, 6 H), 26.26 (dd, J = 14, 140 Hz), 30.00 (d, J = 84 Hz), 128.62 (d, J = 11 Hz), 130.68 (d, J = 10 Hz), 131.73 (d, J = 2 Hz), 132.61 (d, J = 98 Hz) ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 30.58, 32.01 ppm. MS (ESI/TOF): m/z = 381
[M + H]⁺. HRMS: m/z calcd for C₁₉H₂₆O₄NaP₂: 403.1204; found: 403.1211.
Compound 4c: yellow oil. ^¹H NMR (400 MHz, CDCl₃): δ = 1.18-1.24 (m, 3 H), 1.75-2.08 (m, 4 H), 2.35-2.46 (m, 2H); 3.74-3.80 (m, 1 H), 3.95-4.02 (m, 1 H), 7.39-7.51 (m, 9 H), 7.63-7.72 (m, 6 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 14.63, 16.35 (d, J = 6 Hz), 30.15 (dd, J = 14, 100 Hz), 60.51 (d, J = 6 Hz), 128.58 (d, J = 12 Hz), 130.67 (d, J = 9 Hz), 131.50 (d, J = 10 Hz), 131.68 (s, l), 132.22-132.27 (m)ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 32.17, 43.68 ppm. MS (ESI/TOF): m/z = 413 [M + H]⁺. HRMS: m/z calcd for C₂₃H₂₆O₃NaP₂: 435.1255; found: 435.1258.
Compound 4d: white solid, mp 145-148 ˚C. ^¹H NMR (400 MHz, CDCl₃): δ = 1.37 (d, J = 12.0 Hz, 6 H), 1.85-1.94 (m, 4 H), 2,37-4,48 (m, 2 H), 7.40-7.47 (m, 6 H), 7.69 (t, J = 8.8 Hz, 4 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 14.85, 16.03 (d, J = 68 Hz), 22.12, 30.24 (dd, J = 12, 71 Hz), 31.77-31.83 (m), 32.43 (d, J = 13 Hz), 128.68 (d, J = 12 Hz), 130.62 (d, J = 9 Hz), 131.84 (d, J = 2 Hz), 132.83 ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 32.45, 43.33 ppm. MS (ESI/TOF): m/z = 321 [M + H]⁺. HRMS: m/z calcd for C₁₇H₂₂O₂NaP₂: 343.0993; found: 343.0995.

Compound 4e: yellow oil. ^¹H NMR (400 MHz, CDCl₃): δ = 1.05-1.17 (m, 6 H), 1.58 (d, J = 11.2 Hz, 3 H), 1.65-1.96 (m, 6 H), 3.85-3.92 (m, 4 H), 7.35-7.40 (m, 3 H), 7.58 (s, l, 2 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 15.29 (d, J = 4 Hz), 16.17 (d, J = 70 Hz), 16.27 (t, J = 5 Hz), 26.24 (dd, J = 13, 140 Hz), 31.55-32.69 (m), 61.39 (d, J = 6.4 Hz), 128.58 (d, J = 10 Hz), 128.58 (d, J = 11 Hz), 129.90 (d, J = 8 Hz), 131.62, 133.05 (d, J = 97 Hz)ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 30.42, 36.84 ppm. MS (ESI/TOF): m/z = 319 [M + H]⁺. HRMS: m/z calcd for C₁₄H₂₄O₄NaP₂: 341.1048; found: 341.1046.
Compound 4f: colorless oil. ^¹H NMR (400 MHz, CDCl₃):
δ = 1.03-1.17 (m, 3 H), 1.53 (t, J = 12.8 Hz, 3 H), 1.58-1.98 (m, 6 H), 3.61-3.71 (m, 1 H), 3.83-3.93 (m, 1 H), 7.26-7.42 (m, 6 H), 7.48-7.62 (m, 4 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 14.53-14.65 (m), 15.54, 15.76, 16.22-16.46 (m), 29.67 (t, J = 14 Hz), 30.67 (t, J = 14 Hz), 31.70 (t, J = 12 Hz), 32.39 (t, J = 12 Hz), 57.46, 60.34-60.45 (m), 128.42-128.62 (m), 129.57 (d, J = 20 Hz), 129.83 (d, J = 9 Hz), 130.79 (d, J = 20 Hz), 131.38 (d, J = 10 Hz), 131.51-131.61 (m), 132.16-132.35 (m), 132.44 (d, J = 20 Hz), 133.39 (d, J = 20 Hz)ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 36.74 (d, J = 3.4 Hz), 36.85, 43.27 (d, J = 3.5 Hz), 43.44 ppm. MS (ESI/TOF): m/z = 351 [M + H]⁺. HRMS: m/z calcd for C₁₈H₂₄O₃NaP₂: 373.1098; found: 373.1097.
Compound 4g: dark oil. ^¹H NMR (400 MHz, CDCl₃): δ = 1.08-1.49 (m, 8 H), 1.71-2.09 (m, 4 H), 3.88-4.16 (m, 4 H), 7.28-7.60 (m, 6 H), 7.63-8.87 (m, 3 H) ppm. ^¹³C NMR (100 MHz, CDCl₃): δ = 0.98, 16.38 (d, J = 5 Hz), 19.68, 22.64, 29.30, 29.40, 29.64, 31.86, 61.59 (d, J = 6 Hz), 128.40, 128.55, 128.67, 130.45, 131.00 (d, J = 11 Hz), 131.50, 131.87 (d, J = 11 Hz), 133.67 ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 30.66, 42.12 ppm. MS (ESI/TOF): m/z = 397
[M + H]⁺. HRMS: m/z calcd for C₁₉H₂₆O₃NaP₂S: 419.0976; found: 419.0981.
Compound 4h: colorless oil. ^¹H NMR (400 MHz, CDCl₃):
δ = 1.23 (t, J = 6.8 Hz, 6 H), 1.28 (t, J = 6.8 Hz, 6 H), 1.72-1.96 (m, 12 H), 3.96-4.10 (m, 8 H), 7.47-7.54 (m, 3 H), 7.67-7.72 (m, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 15.14 (t, J = 4 Hz), 16.34 (t, J = 6 Hz), 26.34 (dd, J = 14, 140 Hz), 30.37 (dd, J = 14, 68 Hz), 61.52 (d, J = 6 Hz), 128.76 (d, J = 11 Hz), 130.41 (d, J = 9 Hz), 131.28 (d, J = 92 Hz), 131.82 (d, J = 3 Hz) ppm. ^³¹P NMR (160 MHz, CDCl₃): δ = 30.45, 30.48, 39.71 ppm. MS (ESI/TOF): m/z = 483 [M + H]⁺. HRMS: m/z calcd for C₂₀H₃₇O₇NaP₃: 505.1650; found: 505.1645.