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2nd August 2010 @ 09:14
Intermediate for the preparation of 1,1-Binaphthyl-2,2-disulfonate – a strong achiral Brønstedt-acid, intended for determination and optimization of the reaction conditions for the acid-catalyzed Pictet-Spengler reaction [1,2]

Reaction Scheme MW45-1


Hazard and Risk Assessment:
Reaction Class: 2
Hazards: T toxic, X Irritant, C Corrosive, F Flammable
Risk rating: U = Unlikely

Start time: 4:30 AM 02/08/2010
End time:

Procedure: [1]
To an ice cooled solution of (+/-)-1,1’-bi(2-naphthol) (1.00g, 3.49 mmol) in dry DMF (10 mL) under argon was added sodium hydride (350 mg, 8.73 mmol, 2.5 eq.; 60% oil dispersion), warmed to room temperature and stirred for 10 min. The resulting yellow solid was slightly heated to obtain a yellow dispersion. To the dispersion N,N-dimethylthiocarbamoyl chloride (950 mg, 7.68 mmol, 2.2 eq.) was added at room temperature and heated to 85°C for 1.5 h.
The yellow-brown mixture was cooled to room temperature and poured into 1% aqueous KOH solution (30 mL). The pale brown solid was filtered off, washed with water and dissolved in DCM. The organic layer was separated from the remaining water, washed with brine and dried over sodium sulfate. After evaporation of the solvent a pale yellow solid was obtained.

Crude product:
1.83 g (3.98 mmol, 114%) of pale yellow solid MW45-1,
1H/13C NMR showed a good purity of the product, but remaining DMF

[1] “Pyridinium 1,1′-Binaphthyl-2,2′-disulfonates as Highly Effective Chiral Brønsted Acid−Base Combined Salt Catalysts for Enantioselective Mannich-Type Reaction”, M. Hatano, T. Maki, K. Moriyama, M. Arinobe and K. Ishihara, J. Am. Chem. Soc. 2008, 130, 16858–16860; DOI: 10.1021/ja806875c.

[2] “A Powerful Chiral Counteranion Motif for Asymmetric Catalysis”, P. García-García, F. Lay, P. García-García, C. Rabalakos, B. List, Angew. Chem. Int. Ed. 2009, 48, 4363 –4366; DOI: 10.1002/anie.200901768.

Procedure from the reference: [1]
(3):1,2 An ice cooled solution of (R)-BINOL (14.3 g, 50.0 mmol) in 100 mL of distilled DMF under N2 was treated under vigorously stirring with NaH (4.4 g, 110 mmol; 60% oil dispersion). To the resulting yellow solution was added N,N-dimethylthiocarbamoyl chloride (13.6 g, 110 mmol) at 0 °C, and the solution was warmed at 85 °C for 1 h by monitoring with the TLC. Then, the reaction mixture was cooled to room temperature and poured into 1% aqueous KOH (300 mL). The colorless precipitate was filtered, washed thoroughly with water, and dissolved in CH2Cl2.
The CH2Cl2 solution was dried over MgSO4 and evaporated to obtain a colorless solid that was recrystallized from CHCl3/hexane (20.2 g, 88% yield). 1H NMR (300 MHz, CDCl3) δ 2.52 (s, 6H), 3.08 (s, 6H), 7.30 (ddd, J = 8.4, 7.1, 0.9 Hz, 2H), 7.42-7.48 (m, 4H), 7.62 (d, J = 8.7 Hz, 2H), 7.91 (d, J = 8.7 Hz, 2H), 7.97 (d, J = 8.7 Hz, 2H). 13C NMR (75 MHz, CDCl3) δ 37.9 (2C), 42.6 (2C), 123.6 (2C), 123.8 (2C), 125.6 (2C), 126.2 (2C), 126.6 (2C), 127.6 (2C), 128.2 (2C), 131.3 (2C), 133.1 (2C), 149.3 (2C), 186.0 (2C). IR(KBr) 2934, 1537, 1394, 1286, 1213, 1136, 1119, 812, 751 cm–1. [α]D
22.8 = +156.1 (c 1.0, CHCl3). HRMS(FAB+) calcd for 26H24N2O2S2 [M]+ 460.1279, found 460.1276.
Attached Files
Reaction Scheme MW45-1