Reaktion #1471502

Reaktionsgleichung

6,8-dimethyl-7-hydroxychroman-4-one

imidazole

triisopropylsilyl chloride

→

6,8-Dimethyl-7-triisopropylsilyloxychroman-4-one

Lösungsmittel

water

dimethylformamide

Reaktionsbedingungen

Aufarbeitung

1. 1
   Extraktionextracted with ether (2x)
2. 2
   WaschenThe combined organic phase was washed with 1N lithium chloride (2x) and brine
3. 3
   Trocknendried over magnesium sulfate
4. 4
   Einengenconcentrated
5. 5
   Sonstigechromatographed on silica gel (1×4 inches packed in hexane) with elution proceeding
6. 6
   Sonstigeto be suitable for further transformations without additional purification

Vorschrift

A mixture of 6,8-dimethyl-7-hydroxychroman-4-one (the compound of Preparation 26, 0.50 g, 2.60 mmol), imidazole (0.35 g, 5.14 mmol), and triisopropylsilyl chloride (0.61 mL, 2.85 mmol) in dimethylformamide (10 mL) was stirred at ambient temperature overnight. The reaction was diluted with water and extracted with ether (2x). The combined organic phase was washed with 1N lithium chloride (2x) and brine, dried over magnesium sulfate and concentrated. The residue was flash chromatographed on silica gel (1×4 inches packed in hexane) with elution proceeding as follows: 5% ethyl acetate/hexane (100 mL), nil; 5% ethyl acetate/hexane (100 mL) and 10% ethyl acetate/hexane (150 mL), 0.529 g (58%) of 6,8-dimethyl-7-triisopropylsilyloxychroman-4-one as a waxy lemon yellow solid which had: NMR δ7.57 (s, 1 H), 4.52 (t, J=6.4 Hz, 2 H), 2.74 (t, J=6.4 Hz, 2 H), 2.21 (s, 3 H), 2.11 (s, 3 H), 1.40-1.26 (m, 3 H), 1.13 (d, J=7.2 Hz, 18 H); 13C NMR δ191.60, 160.25, 159.93, 125.91, 122.55, 116.15, 115.29, 67.24, 37.52, 17.91, 17.69, 17.38, 14.24, 12.28, 9.97. A small silyl impurity was noted in the proton NMR at 1.06 ppm however, the material was found to be suitable for further transformations without additional purification.

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