An expedient enantioselective route to diaminotetralins: Application in the preparation of analgesic compounds

Organic Letters

Volumn 4, Issue 20, 2002, Pages 3465-3468

  Lautens, Mark ^a   Fagnou, Keith ^a   Zunic, Valentin ^a  

^a UNIVERSITY OF TORONTO   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

ANALGESIC AGENT; TETRALIN DERIVATIVE;

ARTICLE; CATALYSIS; CHEMICAL STRUCTURE; CHEMISTRY; CYCLIZATION; STEREOISOMERISM; SYNTHESIS;

ANALGESICS; CATALYSIS; CYCLIZATION; MOLECULAR STRUCTURE; STEREOISOMERISM; TETRAHYDRONAPHTHALENES;

EID: 0037015427     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol026579i     Document Type: Article

References (30)

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18. These challenges likely contribute to the diminished focus on vinylaziridines in π-allylmetal chemistry compared to vinyl epoxides.
19. Lautens, M.; Fagnou, K. Unpublished results.
20. Use of high reaction concentration (∼2.5 M) is key to obtaining high yields. Under lower concentrations, yields of 10-20% are typically obtained. See the Supporting Information.
21. Yields of up to 80% can be obtained with recourse to chromatographic purification techniques.
22. This temperature effect has previously been observed in the ring opening of oxabicycles: Lautens, M.; Fagnou, K. J. Am. Chem. Soc. 2001, 123, 7170-7171.
23. The relative trans stereochemistry was proven for N-Tos 5 by X-ray crystallography.
24. For a review on halide effects in transition metal catalysis, see: Fagnou, K.; Lautens, M. Angew. Chem., Int. Ed. 2002, 41, 26.
25. Application of these new conditions to the asymmetric ring opening of oxabicyclic alkenes will be reported in due course.
26. The absolute stereochemistry of the ring opened products was shown to be (1S,2S) by X-ray crystallography. Crystals suitable for X-ray analysis were obtained by deprotecting N-Boc 10, followed by protection of the free amine with 4-bromobenzenesulfonyl chloride. This is the opposite sense of induction that we have observed for the oxabicyclic series using the same sense of chirality in the ligands.
27. This ligand was prepared from (R)-2-methyl-CBS-oxazaborilidine: Schwink, L.; Knochel, P. Chem. Eur. J. 1998, 4, No.5, 950.
28. We screened a variety of typical high boiling solvents and found that while DMF and toluene gave the product in decent ee (80% and 79% ee, respectively), THP was the preferred solvent.
29. We have previously observed that halide and protic additives were necessary for the addition of pyrrolidine to oxabicycles. The higher temperatures used in our present reaction conditions most likely facilitate reversible binding of the basic amine to the metal center. See ref 10.
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