Synthesis of bridged azabicycles from isoquinolines via a tandem of allylboration and intramolecular metathesis |
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Authors: | N Yu Kuznetsov K A Lyssenko A S Peregudov Yu N Bubnov |
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Institution: | (1) A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 ul. Vavilova, 119991 Moscow, Russian Federation |
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Abstract: | A method for the synthesis of bridged azabicyclic compounds from isoquinolines was developed. The method is based on a combination
of allylboration and ruthenium-catalyzed intramolecular metathesis. Reductive 1,3-diallylation of bromoisoquinolines with
triallylborane gave trans-1,3-diallyl-1,2,3,4-tetrahydroisoquinolines. When heated with triallylborane, these compounds yielded mixtures of cis-and trans-isomers in the ratio ∼1: 1. The structure of cis-1,3-diallyl-5-bromo-1,2,3,4-tetrahydroisoquinoline was confirmed by X-ray diffraction analysis. In a similar way, trans-3-allyl-1-vinyl-1,2,3,4-tetrahydroisoquinoline synthesized by sequential vinylation (with vinyllithium) and allylboration
of isoquinoline, yielded a mixture of cis-and trans-isomers in the ratio 1.6: 1. Intramolecular metathesis reactions of N-Boc derivatives of cis-isomers in the presence of the Grubbs catalyst (2.0–2.5 mol.%) afforded 7,8-benzo-10-azabicyclo4.3.1]dec-2-enes or 7,8-benzo-9-azabicyclo3.3.1]non-2-ene
in nearly quantitative yields.
Dedicated to Academician V. A. Tartakovsky on the occasion of his 75th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1510–1515, August, 2007. |
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Keywords: | triallylborane allylboranes allylboronation nitrogen-containing heterocycles cyclization isoquinolines metathesis |
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