Synlett 2009(1): 97-99  
DOI: 10.1055/s-0028-1087480
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Palladium-Catalysed Cascades Triggered by Dehydrogenation of Secondary or Tertiary Amines: Access to Bridged- and Fused-Ring Heterocycles

Ronald Grigg*a, Anoma Somasunderama, Visuvanathar Sridharana, Ann Keepb
a Molecular Innovation, Diversity and Automated Synthesis (MIDAS) Centre, School of Chemistry, Leeds University, Leeds LS2 9JT, UK
Fax: +44(113)3436501; e-Mail: r.grigg@leeds.ac.uk;
b Johnson Matthey, Orchard Road, Royston, Hertfordshire SG8 5HE, UK
Further Information

Publication History

Received 22 September 2008
Publication Date:
12 December 2008 (online)

Abstract

Palladium-catalysed cascades triggered by dehydrogenation of secondary or tertiary amines and trapping the intermediate imines with cycloadditions and Mannich reactions result in a range of bridged- and fused-ring heterocyclic motifs in moderate to good yields.

    References and Notes

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9

1,2-Benzo-4,7-imino-4-methoxycarbonyl- exo -6-benzyl-oxycarbonylcyclohept-1-ene (7)
Methyl 1,2,3,4-tetrahydroisoquinoline-3-carboxylate (1, 0.1 g, 0.5 mmol), benzyl acrylate (0.17 g, 1.0 mmol), and Pd black (0.0055 g, 0.05 mmol) were mixed in toluene (15 mL) and heated at 110 ˚C for 15 h. After removal of the solvent the residue was purified by column chromatography eluting with Et2O-PE (1:1, v/v) to afford 7 (0.091 g, 50%) as a colourless semisolid and 8 (10%). Anal. Calcd (%) for C21H21NO4: C, 71.79; H, 5.98; N, 3.99. Found: C, 71.70; H, 6.20; N, 4.05. ¹H NMR (300 MHz, CDCl3): δ = 7.15-7.07 (m, 4 H, ArH), 5.12 (s, 2 H, CH2Ph), 4.57 (s, 1 H, Ha), 3.79 (s, 3 H, CO2Me), 3.26 (d, 1 H, J = 16.60 Hz, ArCHH), 3.14 (dd, 1 H, J = 8.85, 2.60 Hz Hb), 3.02 (d, 1 H, J = 16.60 Hz, ArCHH), 2.47 (dd, 1 H, J = 13.75, 2.60 Hz, Hc), 2.22 (dd, 1 H, J = 13.75, 8.85 Hz, Hd). MS: m/z (%) = 351 (0.2) [M+], 292 (3), 260 (0.4), 189 (100), 157 (18).