An effective method for the preparation of mono N-alkyl derivatives of 1,1′-bis(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) |
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Authors: | Benjamin K.H. Chan |
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Affiliation: | School of Chemistry, The University of New South Wales, UNSW Sydney, NSW 2052, Australia |
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Abstract: | The condensation of 1,1′-bis(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) with alkyl, aralkyl and aryl aldehydes, but not ketones, in ethanol or chloroform provides useful cyclic aminal [8-substituted 5,6,10,11,15b,15c-hexahydro-2,3,13,14-tetramethoxy-8H-imidazo[5,1-a:4,3-a′]diisoquinoline] intermediates that when subsequently treated with sodium cyanoborohydride in ethanol, followed by the addition of 2 M hydrochloric acid, gave monosubstituted N-alkyl 1,1′-bis(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) derivatives in very high yields. The rates of the initial condensation with four different aldehydes were measured, and the entire sequence was successfully applied in one example to a ‘one-pot’ process; this signals a versatile route to differentially N-substituted 1,1′-bis(1,2,3,4-tetrahydroisoquinoline) derivatives. |
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Keywords: | 1,1&prime -Bis(1,2,3,4-tetrahydroisoquinoline) Reductive alkylation Condensation Ligands Reaction rates |
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