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TCI Practical Example: Regioselective Acylation with MeTAPS-Br

We are proud to present the regioselective acylation of a primary hydroxyl group of 1,2-diol using MeTAPS-Br as a catalyst.

Used Chemicals

• 1-Phenylethane-1,2-diol [P0686]
• Isobutyric Anhydride [I0111]
• MeTAPS-Br [H1748]
• Triethylamine [T0424]
• Toluene

Procedure

The solution of 1-phenylethane-1,2-diol (0.20 g, 1.4 mmol), isobutyric anhydride (0.34 g, 2.1 mmol), MeTAPS-Br (65 mg, 0.14 mmol), and triethylamine (0.29 g, 2.9 mmol) in toluene (2 mL) was stirred for 2 h at room temperature under nitrogen atmosphere. The reaction mixture was directly purified by column chromatography (1 : 10 ethyl acetate / hexane on silica gel), giving 2-hydroxy-2-phenylethyl isobutyrate as colorless oil (0.22 g, 73% yield).

Experimenter's Comments

The reaction mixture was monitored by ¹H NMR.
The acylation selectivity was (1°-OH) : (2°-OH) = 97 : 3 (mol ratio) after the reaction.
The undesired 2°-OH product was removed by column chromatography.

Analytical Data

2-Hydroxy-2-phenylethyl isobutyrate

¹H NMR (400 MHz, CDCl₃); δ 7.43-7.28 (m, 5H), 4.96 (dd, J = 8.2, 3.7 Hz, 1H), 4.29 (dd, J = 11.7, 3.4 Hz, 1H), 4.19 (dd, J = 11.5, 8.2 Hz, 1H), 2.65 (br, 1 H), 2.60 (sept, J = 6.9 Hz, 1H), 1.17 (d, J = 6.9 Hz, 6H).

¹³C NMR (101 MHz, CDCl₃); δ 177.5, 140.0, 128.7 (2 C), 128.4, 126.3 (2 C), 72.7, 69.3, 34.1, 19.1 (2 C).

Lead Reference

• A Phosphonium Ylide as an Ionic Nucleophilic Catalyst for Primary Hydroxyl Group Selective Acylation of Diols
• Y. Toda, T. Sakamoto, Y. Komiyama, A. Kikuchi, H. Suga, ACS Catal. 2017, 7, 6150.