| Abstract
| - New chiral isoquinolinium salt derivatives 1,2 or 3 have been treated with Grignard reagentstogive as major products, 1-substituted 1,2-dihydroisoquinolines4a−f, oxazolidine derivatives10a−for 21, respectively, in good yield and in moderate to gooddiastereoisomeric excess. Thestereochemistry of these new derivatives has been elucidated, inparticular, by X-ray crystallographicstudies of 1,2-dihydroisoquinoline 4b and the minoroxazolidine 11b. Reduction of all theseintermediates gave chiral 1-substituted 1,2,3,4-tetrahydroisoquinolinessuch as base 8. Theenantioselective synthesis of the natural alkaloid (−)-salsonidine inthree steps and 38% overallyield from salt 3 is described as an application.Reduction of salt 2 gave a new oxazolidinederivative15 which is a practical intermediate for the synthesis of3-alkyl 1,2,3,4-tetrahydroisoquinolines17a,b, while oxazolidines such as 10 areconvenient precursors of 1,3-disubstituted tetrahydroisoquinolines, as illustrated by a synthesis of 1,3-dimethyltetrahydroisoquinoline 20.
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