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DOI: 10.1055/s-0030-1260952
Palladium-Catalysed Cyclisation of α-Hydroxy Allylic Acetates: A Formal Synthesis of (±)-Swainsonine
Publikationsverlauf
Publikationsdatum:
14. Juli 2011 (online)
Abstract
A hydroxy group in the allylic position directed the stereochemistry of cyclisation of allylic acetates to form nitrogen heterocycles, giving the trans isomer for the piperidine and the cis isomer for the pyrrolidine. A formal synthesis of (±)-swainsonine was achieved.
Key words
piperidine - palladium - pyrrolidine - alkaloid - cyclisation
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References and Notes
A solution of allylic acetate 9 (389 mg, 1.05 mmol), tetrakis(triphenylphosphine)palladium(0) (60 mg, 5 mol%), and tetramethyl guanidine (131 µL, 1.05 mmol) in THF (5 mL) under nitrogen was stirred at r.t. for 4 h. The mixture was then concentrated in vacuo, and the residue was purified by flash chromatography (silica gel, 30% EtOAc-hexane) to give piperidine 10 (mixture of isomers) as a colourless oil. Major isomer: ¹H NMR (400 MHz, CDCl3): δ = 8.12-8.05 (1 H, m), 7.71-7.62 (3 H, m), 5.75 (1 H, ddd, J = 17, 11, 5 Hz), 5.24 (1 H, ddd, J = 11, 2, 1 Hz), 5.23 (1 H, ddd, J = 17, 2, 1 Hz), 4.51 (1 H, m), 3.95 (1 H, m), 3.83 (1 H, br d, J = 13 Hz), 3.24 (1 H, dt, J = 13, 3 Hz), 1.98-1.85 (1 H, m), 1.78-1.63 (2 H, m), 1.49 (1 H, m). ¹³C NMR (100 MHz, CDCl3): δ = 148.0, 133.7, 133.4, 132.0, 131.8, 131.1, 124.3, 124.1, 118.9, 67.5, 61.6, 41.9, 25.6, 19.0.
8The corresponding t-Boc and aloc-protected substrates failed to cyclise under these conditions.
13Details have been deposited with the Cambridge Crystallographic Database, CCDC 819544, and may be obtained at http://www.ccdc.cam.ac.uk.
16Details have been deposited with the Cambridge Crystallographic Database, CCDC 819546, and may be obtained at http://www.ccdc.cam.ac.uk.