Synlett 2002(3): 0468-0470
DOI: 10.1055/s-2002-20467
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© Georg Thieme Verlag Stuttgart · New York

Efficient and Selective Cleavage of t-Butoxycarbonyl Group from Carbamates and Amides by CeCl3·7H2O-NaI

J. S. Yadav*, B. V. Subba Reddy, K. Srinivasa Reddy
Organic Chemistry Division-I, Indian Institute of Chemical Technology, Hyderabad-500 007, India
Fax: +91(40)7170512; e-Mail: yadav@iict.ap.nic.in;
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Publikationsverlauf

Received 31 October 2001
Publikationsdatum:
05. Februar 2007 (online)

Abstract

A highly selective cleavage of the t-butoxycarbonyl group has been achieved in high yields using CeCl3·7H2O-NaI in acetonitrile at ambient temperature under neutral conditions. This method is mild and compatible with a wide range of functional groups such as THP, TBDMS, TBDPS, trityl ethers, mono-BOC or Cbz protected amines, acetamide, sulfonamide and benzamide etc., present in the substrate.

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Experimental Procedure: A mixture of di-BOC derivative (5 mmol), CeCl3·7 H2O (5 mmol) and sodium iodide (5 mmol) in acetonitrile (10 mL) was stirred at ambient temperature for an appropriate time (Table). After complete conversion, as indicated by TLC, the reaction mixture was diluted with water (25 mL) and extracted with ethyl acetate (2 × 20 mL). The combined organic layers were washed with brine, dried over anhyd Na2SO4 and concentrated in vacuo, and the resulting product was purified by column chromatography on silica gel (Merck, 100-200 mesh, ethyl acetate-hexane, 2:8) to afford pure mono-BOC protected amine. Spectroscopic Data of 1a: [α]D 25 = -38.2 (c 1.5, CHCl3). 1H NMR (CDCl3): δ = 1.45 (s, 18 H), 3.60 (dd, 2 H, J = 5.5, 13.6 Hz), 3.65 (s, 3 H), 5.38 (dd, 1 H, J = 5.5, 10.3 Hz), 7.28-7.42 (m, 15 H). 2a: [α]D 25 = +11.3 (c 1.5, CHCl3). 1H NMR (CDCl3): δ = 1.40 (s, 9 H), 3.38 (dd, 2 H, J = 5.5, 13.6 Hz), 3.75 (s, 3 H), 4.38 (m, 1 H), 5.35 (brd, NH, J = 8.0 Hz), 7.10-7.40 (m, 15 H). 1b: [α]D 25 = -29.789 (c 1.5, CHCl3). 1H NMR (CDCl3): δ = 0.03 (s, 6 H), 0.85 (s, 9 H), 1.48 (s, 18 H), 3.67 (s, 3 H), 4.10 (dd, 2 H, J = 5.8, 13.7 Hz), 5.10 (dd, 1 H, J = 5.8 and 10.5 Hz). 2b: [α]D 25 = +17.684 (c 1.5, CHCl3). 1H NMR (CDCl3): δ = 0.02 (s, 6 H), 0.84 (s, 9 H), 1.43 (s, 9 H), 3.75 (s, 3 H), 3.80 (dd, 1 H, J = 5.8, 13.7 Hz), 4.05 (dd, 1 H, J = 5.8, 13.7 Hz), 4.30 (m, 1 H), 5.23 (brd, NH, J = 7.8 Hz). 1d: [α]D 25 = -11.8 (c 1.5, CHCl3). 1H NMR (CDCl3): δ = 1.03 (s, 9 H), 1.43 (s, 18 H), 3.62 (s, 3 H), 4.18 (dd, 2 H, J = 5.7, 13.8 Hz), 5.23 (dd, 1 H, J = 5.7, 10.3 Hz), 7.38-7.40 (m, 6 H), 7.58-7.65 (m, 4 H). 2d: [α]D 25 = +14.2 (c 1.5, CHCl3). 1H NMR (CDCl3): δ = 1.0 (s, 9 H), 1.45 (s, 9 H), 3.78 (s, 3 H), 3.98 (dd, 2 H, J = 5.7, 13.8 Hz), 4.38 (m, 1 H), 5.32 (br d, NH, J = 8.3 Hz), 7.28-7.43 (m, 6 H), 7.5-7.63 (m, 4 H). 1h: [α]D 25 = -35.57 (c 1.0, CHCl3). 1H NMR (CDCl3): δ = 1.48 (s, 18 H), 2.10 (s, 3 H), 2.43-2.60 (m, 4 H), 3.78 (s, 3 H), 5.05 (dd, 1 H, J = 9.0 and 4.5 Hz). 2h: [α]D 25 = 24.3 (c 2.8, CHCl3), (ref. [5] [α]D 25 = 24.6 (c 2.84, CHCl3)). 1H NMR (CDCl3): δ = 1.33 (s, 9 H), 1.78-1.90 (m, 2 H), 1.98 (s, 3 H), 2.41 (t, 2 H, J = 7.3 Hz), 3.65 (s, 3 H), 4.32-4.41 (m, 1 H), 5.23 (br s, NH). 1j: [α]D 25 = +12.8 (c 1.0, CHCl3). 1H NMR (CDCl3): δ = 0.88 (d, 3 H, J = 6.8 Hz), 1.18 (d, 3 H, J = 6.8 Hz), 1.50 (s, 18 H), 2.42-2.50 (m, 1 H), 3.78 (s, 3 H), 4.48 (d, 1 H, J = 6.8 Hz). 2j: [α]D 25 = -20.8 (c 1.1, MeOH) (ref. [5] [α]D 25 = -21.2 (c 1.1, MeOH)). 1H NMR (CDCl3): δ = 0.85 (d, 3 H, J = 6.8 Hz), 0.90 (d, 3 H, J = 6.8 Hz), 1.50 (s, 9 H), 2.02-2.18 (m, 1 H), 3.75 (s, 3 H), 4.23 (m, 1 H), 4.95 (brs, NH). 1l: [α]D 25 = -37.2 (c 2.15, CHCl3), (ref. [5] [α]D 25 = -37.2 (c 2.15, CHCl3)). 1H NMR (CDCl3): δ = 1.50 (s, 18 H), 2.18 (m, 1 H), 2.40 (m, 2 H), 2.45 (m, 1 H), 3.68 (s, 3 H), 3.75 (s, 3 H), 4.95 (dd, 1 H, J = 9.0 and 4.3 Hz). 2l: [α]D 25 = +12.7 (c 2.00, CHCl3), [ref. [5] [α]D 25 = +12.9 (c 2.00, CHCl3)]. 1H NMR (CDCl3): δ = 1.40 (s, 9 H), 1.90 (m, 1 H), 2.15 (m, 1 H), 2.39 (m, 2 H), 3.65 (s, 3 H), 3.70 (s, 3 H), 3.40 (br s, 1 H), 5.15 (br s, NH). IICT Commun. No: 01/x/10.