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Synlett 2005(20): 3157-3159  
DOI: 10.1055/s-2005-922749
LETTER
© Georg Thieme Verlag Stuttgart · New York

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;
Further Information

Publication History

Received 22 September 2005
Publication Date:
28 November 2005 (online)

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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

    References

  • 1 Katritzky AR. Kirichenko N. Rogovoy BV. He H.-Y. J. Org. Chem.  2003,  68:  9088 ; and references therein
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  • 7a Evidence for this possibility with organopalladium(II) halides has been presented: Cunico RF. Maity BC. Org. Lett.  2003,  5:  4947 
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  • 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
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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].

8

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

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.