Bismuth(III) Chloride Catalyzed Efficient and Selective Cleavage of Trityl Ethers [1]

Abstract

A highly selective and efficient protocol has been developed for detritylation using 5 mol% BiCl₃ in acetonitrile. The ­cleavage proceeds at room temperature in high yields and the conditions are mild enough to tolerate a variety of acid-base sensitive functional groups.

trityl ethers - catalytic - selective - bismuth(III) chloride - alcohols

References

1

IICT Communication No. 031004.

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17

General Procedure. Trityl ether (2 mmol) in dry MeCN (2 mL), was treated with a catalytic amount of BiCl₃ (5 mol%) and stirred at r.t. After complete conversion of the reaction as indicated by TLC, the reaction mixture was filtered through a small pad of Celite. The filtrate was extracted with EtOAc, washed with brine and dried over anhyd Na₂SO₄. After evaporation, the residue was purified by column chromatography using silica gel (60-120 mesh; hexane-EtOAc) to furnish pure alcohol.
Spectroscopic data for selected compounds. Compound 1a: IR (neat): 2941, 1057, 749 cm^-1. ¹H NMR (200 MHz, CDCl₃): δ = 1.92-2.12 (m, 2 H), 2.72 (t, 2 H, J = 10.0 Hz), 3.17 (t, 2 H, J = 5.1 Hz), 7.12-7.35 (m, 15 H), 7.47 (d, 6 H, J = 8.2 Hz). MS: m/z = 378 [M⁺]. Compound 2a: IR (neat): 3355, 2943, 1057, 745 cm^-1. ¹H NMR (300 MHz, CDCl₃): δ = 1.92-2.12 (m, 2 H), 2.72 (t, 2 H, J = 5.2 Hz), 3.63 (t, 2 H, J = 9.8 Hz), 7.15-7.25 (m, 5 H). MS: m/z = 136 [M⁺]. Compound 1d: IR (neat): 2358, 1219, 1109, 773 cm^-1. ¹H NMR (200 MHz, CDCl₃): δ = 1.03 (s, 9 H), 1.38 (s, 2 H), 1.51-1.62 (m, 4 H), 3.02 (t, 2 H, J = 5.9 Hz), 3.62 (t, 3 H, J = 5.2 Hz), 7.16-7.41 (m, 19 H), 7.39 (d, 6 H, J = 7.9 Hz). MS: m/z = 585 [M⁺]. Compound 2d: IR (neat): 3332, 2855, 1104, 1028, 772 cm^-1. ¹H NMR (300 MHz, CDCl₃): δ = 1.03 (s, 9 H), 1.39-1.59 (m, 6 H), 3.59 (t, 2 H, J = 6.0 Hz), 3.64 (t, 2 H, J = 6.0 Hz), 7.33-7.38 (m, 2 H), 7.62 (d, 2 H, J = 7.3 Hz). MS: m/z = 342 [M⁺]. Compound 1e: IR (neat): 2936, 1727, 1156, 1071 cm^-1. ¹H NMR (200 MHz, CDCl₃): δ = 1.19 (s, 9 H), 1.46-1.71 (m, 6 H), 3.06 (t, 2 H, J = 5.9 Hz), 4.03 (t, 2 H, J = 5.9 Hz), 7.18-7.33 (m, 9 H), 7.45 (d, 6 H, J = 8.2 Hz). MS: m/z = 430 [M⁺]. Compound 2e: IR (neat): 3439, 2938, 1728, 1159, 1057 cm^-1. ¹H NMR (200 MHz, CDCl₃): δ = 1.18 (s, 9 H), 1.38-1.72 (m, 6 H), 3.62 (t, 2 H, J = 6.6 Hz), 4.04 (t, 2 H, J = 6.6 Hz). MS: m/z = 188 [M⁺]. Compound 1i: IR (neat): 2361, 1219, 1174, 1060, 771 cm^{- 1}. ¹H NMR (200 MHz, CDCl₃): δ = 3.60 (d, 2 H, J = 6.6 Hz), 3.80 (s, 3 H), 3.85 (d, 2 H, J = 6.5 Hz), 4.30 (s, 2 H), 5.60-5.90 (m, 2 H), 6.76 (d, 2 H, J = 8.2 Hz), 7.15 (d, 2 H, J = 8.1 Hz), 7.30 (m, 9 H), 7.45 (d, 6 H, J = 8.2 Hz). MS: m/z = 450 [M⁺]. Compound 2i: IR (neat): 3418, 2935, 1514, 1174, 1032 cm^-1. ¹H NMR (200 MHz, CDCl₃): δ = 3.80 (s, 3 H), 4.01 (d, 2 H, J = 6.5 Hz), 4.15 (d, 2 H, J = 6.5 Hz), 4.40 (s, 2 H), 5.50-5.90 (m, 2 H), 6.85 (d, 2 H, J = 8.2 Hz), 7.27 (d, 2 H, J = 8.2 Hz). MS: m/z = 208 [M⁺]. Compound 1n: IR (neat): 2985, 2935, 1611, 1509, 1216, 1077 cm^-1. ¹H NMR (200 MHz, CDCl₃): δ = 1.31 (s, 6 H), 1.45 (s, 3 H), 1.53 (s, 3 H), 3.50-3.63 (m, 2 H), 3.90 (dt, 1 H, J = 6.0 and 2.3 Hz), 4.20-4.30 (m, 2 H), 4.48-4.58 (m, 2 H), 5.50 (d, 1 H, J = 5.1 Hz), 7.20 (m, 9 H), 7.40 (d, 6 H, J = 7.3 Hz). MS: m/z = 503 [M⁺]. Compound 2n: IR (neat): 3425, 2980, 2930, 1509, 1077 cm^-1. ¹H NMR (200 MHz, CDCl₃): δ = 1.31 (s, 6 H), 1.45 (s, 3 H), 1.53 (s, 3 H), 3.60-3.73 (m, 2 H), 3.80 (dt, 1 H, J = 6.0 and 2.3 Hz), 4.20-4.30 (m, 2 H), 4.48-4.58 (m, 2 H), 5.50 (d, 1 H, J = 5.1 Hz). MS: m/z = 260 [M⁺].

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