Enantiospecific stereodivergent synthesis of trans- and cis-N(2),3-dimethyl-4-phenyl-1,2,3,4-tetrahydroisoquinolines. 2010

Steven J Coote, and Stephen G Davies, and Ai M Fletcher, and Paul M Roberts, and James E Thomson
Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK.

The acid-promoted cyclizations of a range of N-benzylethanolamines (derived from pseudoephedrine or ephedrine) give the corresponding trans-N(2),3-dimethyl-4-phenyl-1,2,3,4-tetrahydroisoquinolines with high levels of diastereoselectivity and in good yields of isolated product. The cyclizations of the corresponding chromium tricarbonyl complexes are rendered completely stereoselective. Acid-promoted cyclization of N-(3',4'-dimethoxybenzyl)ephedrine and its chromium tricarbonyl complex occur with complementary diastereoselectivities to give trans- and cis-N(2),3-dimethyl-4-phenyl-6,7-dimethoxy-1,2,3,4-tetrahydro-isoquinoline, respectively, in >99:1 d.r. The latter is consistent with a "double inversion" mechanism, which involves neighboring group participation by the chromium tricarbonyl moiety followed by rearomatization to give the corresponding cis-tetrahydroisoquinoline with overall retention of configuration.

UI MeSH Term Description Entries
D007546 Isoquinolines A group of compounds with the heterocyclic ring structure of benzo(c)pyridine. The ring structure is characteristic of the group of opium alkaloids such as papaverine. (From Stedman, 25th ed)
D003500 Cyclization Changing an open-chain hydrocarbon to a closed ring. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed) Cyclizations
D004809 Ephedrine A phenethylamine found in EPHEDRA SINICA. PSEUDOEPHEDRINE is an isomer. It is an alpha- and beta-adrenergic agonist that may also enhance release of norepinephrine. It has been used for asthma, heart failure, rhinitis, and urinary incontinence, and for its central nervous system stimulatory effects in the treatment of narcolepsy and depression. It has become less extensively used with the advent of more selective agonists. Ephedrine Hydrochloride,Ephedrine Renaudin,Ephedrine Sulfate,Erythro Isomer of Ephedrine,Sal-Phedrine,Ephedrine Erythro Isomer,Hydrochloride, Ephedrine,Renaudin, Ephedrine,Sal Phedrine,SalPhedrine,Sulfate, Ephedrine
D004983 Ethanolamines AMINO ALCOHOLS containing the ETHANOLAMINE; (-NH2CH2CHOH) group and its derivatives. Aminoethanols
D013237 Stereoisomerism The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed) Molecular Stereochemistry,Stereoisomers,Stereochemistry, Molecular,Stereoisomer

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