Multicomponent Polymerization of Alkynes, Sulfonyl Azide, and Iminophosphorane at Room Temperature for the Synthesis of Hyperbranched Poly(phosphorus amidine)s

Published as part of the Cluster Synthesis of Materials

Abstract

The construction of functional hyperbranched polymers with unique topological structures and distinct properties remains a great challenge. Multicomponent polymerization, as a fascinating polymer synthetic approach, has proved to be a powerful tool for the synthesis of polymers with diverse structures and multifunctionalities, which is a great advantage for the preparation of hyperbranched polymers. In this work, a multicomponent polymerization of alkynes, sulfonyl azide, and iminophosphorane is utilized for the construction of heteroatom-rich hyperbranched poly(phosphorus amidine)s with different topological structures and fluorescence response toward platinum group metal ions.

Key words

hyperbranched polymer - multicomponent polymerization - alkynes - poly(phosphorus amidine)s - luminescence

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• 19 Synthesis of Model Compound 6 To a solution of sulfonyl azide 5 (219 mg, 1.2 mmol), alkyne 4 (122 mg, 1.2 mmol), iminophosphorane 3 (353 mg, 1.0 mmol), and CuI (38 mg, 0.2 mmol) in CH₂Cl₂ (8 mL) was added Et₃N (282 μL, 2.0 mmol) with a syringe under a nitrogen atmosphere. The resulting mixture was stirred at r.t. for 8 h. The reaction mixture was concentrated and the residue was subject to silica gel column chromatography (EtOAc/petroleum v/v, 1:1) to give product 6, which was further recrystallized from EtOAc/petroleum to afford a white solid with 84% (513 mg) yield. IR (KBr thin film): 3307, 3056, 2923, 1590, 1544, 1495, 1460, 1342, 1277, 1133 cm⁻¹. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.31 (d, J = 5.2 Hz, 1 H), 7.57 (m, 3 H), 7.47 (m, 12 H), 7.28 (t, J = 7.4 Hz, 1 H), 7.08 (t, J = 7.8 Hz, 2 H), 6.79 (m, 4 H), 6.67–6.56 (m, 8 H) ppm. HRMS: m/z [M + H]⁺ calcd for C38H32N2O2PS: 611.1922; found: 611.1929, m/z [M + Na]⁺ calcd for C38H32N2NaO2PS: 633.1742; found: 633.1743.
• 20 Multicomponent polymerizations were conducted under nitrogen by using the standard Schlenk technique. A typical procedure for the polymerization of 1a, 2, and 3 is given below as an example (see Table 1, entry 4). Alkyne monomer 1a (32 mg, 0.10 mmol), disulfonyl azides 2 (38 mg, 0.10 mmol), iminophosphorane 3 (88 mg, 0.25 mmol), and CuI (4 mg, 0.02 mmol) were added to a 10 mL Schlenk tube equipped with a magnetic stirrer. After purging with dry nitrogen for 3 times, DMF (1.3 mL) and Et₃N (28 μL, 0.20 mmol) were then added. After stirring at r.t. for 1 h, the reaction mixture was diluted with DMF (2 mL) and then precipitated in diethyl ether (200 mL) through a cotton-filled dropper. The precipitates were then collected by filtration and dried under vacuum to constant weight to afford the polymer product. hb-P1: Yellow powder; 79% (107 mg) yield. M _w = 133 100 g/mol, M _w/M _n = 6.90. IR (KBr): 3284, 3053, 3030, 2098, 1588, 1538, 1499, 1436, 1339, 1236, 1132 cm⁻¹. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.31, 7.48, 7.28, 6.81, 6.62, 6.29, 6.01, 4.06 ppm. hb-P2: Yellow powder; 81% (117 mg) yield. M _w = 441 700 g/mol, M _w/M _n = 9.37. IR (KBr): 3290, 3060, 3022, 2104, 1581, 1537, 1484, 1434, 1342, 1234, 1133 cm⁻¹. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.19, 7.45, 7.17, 6.87, 6.76, 6.55, 6.01, 4.14 ppm.