Synthesis of Allylamines fromAlkynes and Iminium Ions

Abstract

The iminium salt Bn₂N⁺=CH₂ SnCl₅ ^- undergoesene reactions with inverse electron demand with alkynes and withthe triple bond of enynes to give benzylideneammonium ions in aprotic solvents.Their hydrolysis yields N-benzylallylaminesin good yields. Mannich reaction products, which are the main productsunder more nucleophilic reaction conditions, have not been detected.

Key words

electrophilic additions - ene reactions - enynes - pericyclic reactions

References

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1

New address: S. Rehn, Dr. Th. BöhmeKG Chemische Fabrik GmbH & Co., D-82538 Geretsried, Germany.

13

For the spectroscopic characterization,the precipitated iminium salt 2 was filteredoff, washed with a 1:1 mixture of Et₂O and CH₂Cl₂,and dried in vacuo (yield: 93%). ¹HNMR (CD₃CN, 300 MHz): δ = 5.02(s, 4 H, PhCH ₂), 7.34-7.40 (m,4 H, C₆H₅), 7.45-7.54 (m, 6 H, C₆H₅),7.95 (t, J _HN = 1 Hz,2 H, N⁺=CH₂). ¹³CNMR (CD₃CN, 75.5 MHz): δ = 63.69(t, PhCH₂), 130.31, 130.47,131.10 (3 d, C₆H₅), 131.17 (s, C₆H₅),169.71 (t, J _CN = 11.2Hz, N⁺=CH₂). ¹¹⁹Sn NMR(CD₃CN, 100.7 MHz): δ = -673(m).

28

Reactions at temperatures above theboiling points of volatile enophiles were carried out in a pressuretube that was equipped with a magnetic stir bar, sealed with a screw capand heated in an aluminum block on the heating platform of a magneticstirrer.