Safe and Convenient Reduction of Δ²-Isoxazolines with PMHS-Pd(OH)₂/C [1]

Abstract

A practical and safe reduction methodology for the conversion of Δ²-isoxazolines to 1,3-aminols is developed using polymethylhydrosiloxane-Pd(OH)₂/C. In presence of (Boc)₂O, the isoxazoline was converted into N-Boc protected 1,3-aminol in a one-pot procedure.

Key words

reduction - polymethylhydrosiloxane - Pd(OH)₂/C - isoxazolines

1

IICT communication no. 031210.

References

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• 12 Preparation of Δ ² -Isoxazolines: The cycloaddition is carried out by heating an equimolar mixture of aldoxime, alkene and chloramine-T trihydrate in EtOH for 3 h. See: Hassner A. Rai KML. Synthesis  1989,  57 

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IICT communication no. 031210.

13

Major isomer: ¹H NMR (CDCl₃): δ = 7.28 (m, 5 H), 5.47 (d, 1 H, J = 7.6 Hz, -NH), 5.01 (m, 1 H), 4.20 (q, 2 H, J = 6.9 Hz), 4.19 (m, 1 H), 3.64 (br s, 1 H, -OH), 2.12 (m, 2 H), 1.40 (s, 9 H), 1.29 (t, 3 H, J = 6.9 Hz). ¹³C NMR (CDCl₃): δ = 174.4, 155.1, 141.4, 128.6, 127.3, 126.4, 79.8, 68.3, 61.7, 51.6, 40.7, 28.2, 14.0. Minor isomer: ¹H NMR (CDCl₃): δ = 7.28 (m, 5 H), 5.05 (d, 1 H, J = 7.6 Hz, -NH), 4.98 (m, 1 H), 4.20 (q, 2 H, J = 6.9 Hz), 4.10 (m, 1 H), 3.18 (br s, 1 H, -OH), 2.12 (m, 2 H), 1.37 (s, 9 H), 1.29 (t, 3 H, J = 6.9 Hz). ¹³C NMR (CDCl₃): δ = 174.1, 155.8, 141.8, 128.6, 127.3, 126.4, 79.6, 67.9, 61.6, 51.7, 40.5, 28.2, 14.0. MS (EI): m/z (%) = 323 (M⁺).

14

Major isomer: ¹H NMR (CDCl₃): δ = 7.18 (d, 2 H, J = 8.6 Hz), 6.82 (d, 2 H, J = 8.6 Hz), 5.40 (d, 1 H, J = 7.6 Hz, -NH), 4.95 (m, 1 H), 4.20 (q, 2 H, J = 6.9 Hz), 4.19 (m, 1 H), 3.22 (br s, 1 H, -OH), 2.12 (m, 2 H), 1.41 (s, 9 H), 1.29 (t, 3 H, J = 6.9 Hz). ¹³C NMR (CDCl₃): δ = 174.5, 158.8, 155.1, 133.5, 127.5, 113.9, 79.7, 68.2, 61.6, 55.2, 51.0, 40.7, 28.2, 14.0. Minor isomer: ¹H NMR (CDCl₃): δ = 7.18 (d, 2 H, J = 8.6 Hz), 6.82 (d, 2 H, J = 8.6 Hz), 4.97 (d, 1 H, J = 7.6 Hz, -NH), 4.92 (m, 1 H), 4.20 (q, 2 H, J = 6.9 Hz), 4.07 (m, 1 H), 2.12 (m, 2 H), 1.41 (s, 9 H), 1.29 (t, 3 H, J = 6.9 Hz). ¹³C NMR (CDCl₃): δ = 174.1, 158.7, 155.8, 133.8, 127.3, 113.9, 79.5, 67.9, 61.5, 55.1, 51.2, 40.5, 28.2, 14.0. MS (EI): m/z (%) = 353 (M⁺).