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1.
Org Lett ; 3(21): 3325-7, 2001 Oct 18.
Article in English | MEDLINE | ID: mdl-11594825

ABSTRACT

[reaction: see text]. N-benzoylated quinone imine ketals undergo smooth cycloadditions in a [4 + 2] sense to yield the expected cycloadducts. The crude cycloadducts, when subjected to a short series of simple transformations, produce synthetically useful quantities of 5-methoxyindoles in excellent overall yields.


Subject(s)
Indoles/chemical synthesis , Aldehydes/chemistry , Benzoquinones/chemistry , Chemistry, Pharmaceutical , Imines/chemistry
2.
J Org Chem ; 66(13): 4704-9, 2001 Jun 29.
Article in English | MEDLINE | ID: mdl-11421796

ABSTRACT

Indoles which bear an alkyl substituent in the 3-position undergo a [3 + 2] annulation reaction when treated with 1,1-cyclopropane diesters in the presence of Yb(OTf)(3) resulting in 2,3-cyclopentanoindolines. Typically, the reactions are performed at elevated temperatures or at ultrahigh pressures. In cases where steric crowding is an issue, ultrahigh pressures are required. In reactions involving substituted cyclopropanes, significant regio- and diastereocontrol was observed. When the substituent was aromatic or olefinic, the reactions took place at ambient temperature and pressure. The applicability of this methodology to the preparation of a key tetracyclic subunit of the kopsane alkaloids was demonstrated.


Subject(s)
Alkaloids/chemical synthesis , Alkanes/chemistry , Cyclopentanes/chemical synthesis , Alkaloids/chemistry , Cyclopentanes/chemistry , Cyclopropanes/chemistry , Indoles/chemistry
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