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DOI: 10.1055/s-2004-815431
The First Example of Polymer-supported Alkenyl Iodonium Salts: Efficient Synthesis of β-Functional Enamines
Publication History
Publication Date:
26 January 2004 (online)
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Abstract
Polymer-supported alkenyl(phenyl) iodonium salts were synthesized, which served as effective alkenyl transfer reagents for the preparation of β-functional enamines; the polymer support poly(4-iodostyrene) can be regenerated and recycled.
Key words
polymer-supported alkenylphenyl iodonium salts - poly(4-iodostyrene) - β-functional enamines
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References
Preparation of Polymer-supported Alkenyl Iodonium Tosylate 3: To a solution of methyl-3-amino-crotonate (2a; 1.15 g, 10 mmol) or ethyl-3-benzylamino-crotonate (2b; 2.19 g, 10 mmol) in CH2Cl2 (30 mL), poly{[4-hydroxy(tosyloxy)iodo]styrene} (1.65 g, 3 mmol) was added. The suspension was stirred at 0 °C for 6 h or 2 h, respectively. After the reaction was complete, the CH2Cl2 was evaporated in vacuum to give oily residue. Et2O (20 mL) was added to precipitate the product, which was filtered off and washed with acetone (10 mL × 2) and Et2O (10 mL × 2) to afford the products. Compound 3a: white powder, 1.61 g, N%, 3.09. IR (KBr): ν = 3176, 3076 1629, 1448, 1404, 1263, 1187, 1125, 1035, 1009, 814, 684 cm-1. Compound 3b: white powder, 1.78 g, N%, 2.44. IR (KBr): ν = 3043, 2920, 1625, 1487, 1449, 1170, 1124, 1034, 1009, 814, 683 cm-1.
8General Procedure for the Synthesis of β-Functional Enamines 4: To a suspension of 3a (1.0 g, N: 2.21 mmol/g) in CHCl3 (10 mL) was added the solution of KSCN (0.1 g, 1 mmol) in water (3 mL). After the reaction was complete, the organic layer was separated and dried over anhyd MgSO4. The solvent was removed under vacuum and Et2O was added to the resulting oil to precipitate poly(4-iodostyrene). The solution was submitted to preparative TLC on silica gel with n-hexane-EtOAc (2:1, v/v) as the eluent to afford 143 mg (83%) of 4a, white powder, mp 77-78 °C. IR (KBr): n = 3410, 3312, 2998, 2949, 1672, 1628, 1506, 1434, 1371, 1264, 1185, 1134, 1071, 778, 648 cm-1. 1H NMR (400 MHz, CDCl3): d = 9.26 (s, 1 H), 5.78 (s, 1 H), 3.77 (s, 3 H), 2.39 (s, 3 H). 13C NMR (100 MHz, CDCl3): d = 168.8, 168.7, 113.5, 75.6, 52.0, 23.4. MS (EI): m/z (%) = 172 (38.9) [M+], 113 (71.4), 87 (67.7), 59 (49.5), 42 (100). Anal. Calcd for C6H8N2O2S: C, 41.85; H, 4.68; N, 16.27. Found: C, 41.78; H, 4.59; N, 16.39.