Copper(II) Trifluoromethanesulfonate Catalyzed Addition of a Carbamoylsilane to Aldehyde Imines

Robert F. Cunico; Rajesh K. Pandey; Jianxin Chen; Adalie R. Motta

doi:10.1055/s-2005-922749

LETTER

Copper(II) Trifluoromethanesulfonate Catalyzed Addition of a Carbamoylsilane to Aldehyde Imines

Robert F. Cunico*, Rajesh K. Pandey, Jianxin Chen, Adalie R. Motta
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, USA
e-Mail: rfc@marilyn.chem.niu.edu;

Abstract

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Abstract

The addition of N,N-dimethylcarbamoyl(trimethyl)silane to aldehyde-derived N-methylimines is catalyzed by copper(II) trifluoromethanesulfonate. After hydrolysis, N,N-dimethyl-α-(N-methylamino)amides are formed, isolated as their ethyl carbamate derivatives.

Key words

α-Aminoamides - carbamoylsilane - imine addition - copper trifluoromethanesulfonate - carbenes

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References

1 Katritzky AR. Kirichenko N. Rogovoy BV. He H.-Y. J. Org. Chem. 2003, 68: 9088 ; and references therein

2 Review: Dömling A. Ugi I. Angew. Chem. Int. Ed. 2000, 39: 3168

For current examples, see:

3a Pick R. Bauer M. Kazmaier U. Hebach C. Synlett 2005, 757

3b Basso A. Banfi L. Riva R. Guanti G. J. Org. Chem. 2004, 70: 575

4 Chen J. Cunico RF. Tetrahedron Lett. 2003, 44: 8025

5 Chen J. Pandey RK. Cunico RF. Tetrahedron: Asymmetry 2005, 16: 941

6

General Procedure.
A Schlenk tube fitted with a Teflon vacuum stopcock and micro stirbar was flame heated under vacuum and refilled with Ar. Aldehyde imine (1.0 mmol) and dry benzene (2 mL) were added followed by Cu(OTf)₂ (4 mol% relative to imine), and the mixture stirred at 25 °C. After 15 min, 1 (0.50 mmol) was added, followed by two 0.5-mmol additions at 6-h intervals. The reaction was monitored by NMR using periodic aliquots. After disappearance of 1, the mixture was hydrolyzed (Na₂CO₃), extracted with CH₂Cl₂, dried (Na₂SO₄), and the concentrate dissolved in 5 mL of CH₂Cl₂ and treated (0 °C) with 1.2 mmol of ethyl chloroformate. To this stirred solution was immediately added aq K₂CO₃ (4.5 mmol in 10 mL H₂O) and after 15 min, it was extracted with CH₂Cl₂. The dried concentrate was flash-chromatographed on silica gel (25-35% EtOAc in hexane) and the isolated 4 characterized [IR: neat films; ¹H NMR and ¹³C NMR (11.75 T, CDCl₃); C, H, N combustion analysis].

7a Evidence for this possibility with organopalladium(II) halides has been presented: Cunico RF. Maity BC. Org. Lett. 2003, 5: 4947

7b Additional mechanistic discussions can be found in: Cunico RF. Motta AR. Org. Lett. 2005, 7: 771

8

There is no reaction between 1 and N-methylbenzaldehyde imine at 100 °C.

9 Strongly polarized iminium salts have been shown to easily add 1, even if the imine carbon atom is highly hindered: Chen J. Cunico RF. Tetrahedron Lett. 2002, 43: 8595 ; characterization data for 5 are reported in this work

10

Each of these independently catalyzes the self-condensation of 1. However, TMSOTf will not catalyze the cross-condensation of 1 and 2 to 3.
Compound 4a: mixture of diastereoisomers. IR: 1694, 1650 cm^-1. ¹H NMR: δ (major) = 4.79 (d, J = 11 Hz, 1 H), 4.14 (m, 2 H), 3.14 (s, 3 H), 2.95 (s, 3 H), 2.85, (s, 3 H), 2.04 (m, 1 H), 1.50-1.80 (m, 5 H), 1.10-1.40 (m, 6 H), 0.80-1.10 (m, 2 H); δ (minor) = 4.58 (d, J = 11 Hz, 1 H), 4.20 (m, 2 H), 3.08 (s, 3 H), 2.96 (s, 3 H), 2.85 (s, 3 H), 2.04 (m, 1 H), 1.50-1.80 (m, 5 H), 1.10-1.40 (m, 6 H), 0.80-1.10 (m, 2 H). ¹³C NMR δ (major) = 170.5, 157.1, 61.6, 58.4, 37.3, 36.46, 35.6, 30.0, 29.2, 28.58, 25.7, 14.7; δ (minor) = 169.9, 156.2, 61.6, 58.8, 36.9, 36.52, 35.7, 30.3, 29.5, 28.59, 26.4, 14.8. Anal. Calcd for C₁₄H₂₆N₂O₃: C, 62.19; H, 9.69; N, 10.36. Found: C, 61.97; H, 9.94; N, 10.32.
Compound 4b: IR: 1696, 1661 cm^-1. ¹H NMR: δ = 7.36 (m, 3 H), 7.27 (m, 2 H), 6.28 (s, 1 H), 4.18 (q, J = 7 Hz, 2 H), 3.03 (s, 3 H), 2.85 (s, 3 H), 2.74 (s, 3 H), 1.29 (t, J = 7 Hz, 3 H). ¹³C NMR: δ = 170.7, 157.6, 134.7, 129.1, 129.0, 128.4, 61.8, 60.0, 37.1, 35.7, 31.4, 14.7. Anal. Calcd for C₁₄H₂₀N₂O₃: C, 63.62; H, 7.63; N, 10.60. Found: C, 63.20; H, 7.95; N, 10.31
Compound 4c: IR: 1694, 1658 cm^-1. ¹H NMR: δ = 7.19 (d, J = 9 Hz, 2 H), 6.90 (d, J = 9 Hz, 2 H), 6.20 (s, 1 H), 4.18 (q, J = 7 Hz, 2 H), 3.82 (s, 3 H), 3.01 (s, 3 H), 2.85 (s, 3 H), 2.73 (s, 3 H), 1.28 (t, J = 7 Hz, 3 H). ¹³C NMR: δ = 170.9, 159.6, 157.5, 130.4, 126.6, 114.3, 61.6, 59.5, 55.3, 37.0, 35.7, 31.2, 14.6. Anal. Calcd for C₁₅H₂₂N₂O₄: C, 61.21; H, 7.53; N, 9.52. Found: C, 61.06; H, 7.78; N, 9.43.
Compound 4d: IR: 1698, 1660 cm^-1. ¹H NMR: δ = 7.45 (s, 1 H), 6.39 (m, 2 H), 6.28 (s, 1 H), 4.18 (q, J = 7 Hz, 2 H), 3.01 (s, 3 H), 2.95 (s, 3 H), 2.84 (s, 3 H), 1.29 (t, J = 7 Hz, 3 H). ¹³C NMR: δ = 168.0, 157.0, 147.8, 143.3, 110.9, 110.5, 61.8, 54.4, 37.0, 35.9, 31.3, 14.6. Anal. Calcd for C₁₂H₁₈N₂O₄: C, 56.68; H, 7.13; N, 11.02. Found: C, 56.65; H, 7.04; N, 10.71.
Compound 4e: IR: 1697, 1650 cm^-1. ¹H NMR: δ = 7.35 (d, J = 5 Hz, 1 H), 7.00 (m, 2 H), 6.46 (s, 1 H), 4.19 (q, J = 7 Hz, 2 H), 3.02 (s, 3 H), 2.98 (s, 3 H), 2.84 (s, 3 H), 1.29 (t, J = 7 Hz, 3 H). ¹³C NMR: δ = 169.8, 157.1, 137.1, 128.3, 127.1, 126.7, 61.8, 54.8, 37.2, 35.8, 30.9, 14.6. Anal. Calcd for C₁₂H₁₈N₂O₃S: C, 53.31; H, 6.71; N, 10.36. Found: C, 53.38; H, 6.65; N, 10.18.
Compound 4f: IR: 1684, 1644 cm^-1. ¹H NMR: δ = 6.12 (s, 1 H), 4.19 (m, 2 H), 4.14 (s, 8 H), 3.37 (s, 3 H), 3.06 (s, 3 H), 2.81 (s, 3 H), 1.27 (t, J = 7 Hz, 3 H). ¹³C NMR: δ = 170.0, 156.7, 82.3, 70.0, 69.4, 68.7, 68.5, 68.3, 61.7, 52.8, 38.0, 35.7, 30.1, 14.7. Anal. Calcd for C₁₈H₂₄FeN₂O₃: C, 58.08; H, 6.50; N, 7.53. Found: C, 58.36; H, 6.40; N, 7.11.