Reductive allylation of pyrrole with allylboranes. Synthesis oftrans- andcis-2,5-disubstituted pyrrolidines |
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Authors: | Yu N Bubnov E V Klimkina L I Lavrinovich A Yu Zykov A V Ignatenko |
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Institution: | (1) N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 117913 Moscow, Russian Federation;(2) A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 ul. Vavilova, 117813 Moscow, Russian Federation |
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Abstract: | Pyrrole undergoes reductive mono- and diallylation on successive treatment with β,γ-unsaturated organoboron derivatives (triallylborane,
allyl(dipropyl)borane, and triprenylborane) and alcohols to give 2-allylated 3-pyrrolines andtrans-2,5-diallylated pyrrolidines. The addition of both the first and second boron-allylic fragment to the heterocycle proceeds
with rearrangement. A method for transformation of thetrans-2,5-diallylpyrrolidine into thecis-isomer (heating with triallylborane at 190 °C) was developed and a series ofN-substituted derivatives of these pyrrolidines was synthesized. A method for the preparative synthesis of nonsymmetrically
substitutedtrans- andcis-2-alkyl(phenyl)-5-allylpyrrolidines, based on reductive allylboration of pyrrole followed by 1,2-addition of RLi to the 5-allyl-1-pyrroline
that formed, was also developed. A direct confirmation of intermediate formation of 2H- and 3H-pyrrole tautomers under the action of allylboranes was obtained. The adduct of 2H-pyrrole with BF3 was detected by NMR spectroscopy.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1718–1728, September, 1999. |
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Keywords: | pyrrole reductive allylboration allylboranes triprenylborane allylic rearrangement alkyl(aryl)lithium 2 5-substituted pyrrolidines trans→ cis-isomerization 2-allylated 3-pyrrolines sigmatropic [1 3]- and [1 5]-hydrogen shifts adduct of 2H-pyrrole with BF3 |
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