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Asymmetric Induction in the Amine Induced Ring-Opening of 3-Bromo-5-ethyl-2-isopropylthiophene-1,1-dioxide Using L-Prolinol

Tsirk, Anders; Gronowitz, Salo LU and Hörnfeldt, Anna-Britta LU (1998) In Acta Chemica Scandinavica 52(5). p.533-540
Abstract
The diastereomers (1-(2S)-[(2R) (3E,5Z)-5-bromo-7-methyl-3,5-octadien-2-yl]-tetrahydro-1H-pyrrol-2yl) methanol (6) and (1-(2S)-[(2S)(3E,5Z)-5-bromo-7-methyl-3, 5-octadien-2-yl] tetrahydro-1H-pyrrol-2-yl) methanol 7) were formed in a 65:35 ratio from 3-bromo-5-ethyl-2-isopropylthiophene, 1,1-dioxide (5) and L-prolinol. (5R,5aS,8R,9R,9aS,9bS)-Ethyl 7-bromo-8-isopropyl-5-methyl-2,3 ,5,5a,8,9,9a,9b-octahydro-1H-pyrrolo[2,1-a] isoindole-9-carboxylate (10) and (5S,5aS,8R,9R,9aS,9bS)-ethyl 7-bromo-8-isopropyl-5-methyl-2,3,5,5a,8, octahydro-1H-pyrrolo[2,1-a]isoindole-9-carboxylate (12) were synthesized from 6 and 7 in order to establish the absolute configuration of the ring-opened products. The asymmetric induction at C(2) in the ring-opened... (More)
The diastereomers (1-(2S)-[(2R) (3E,5Z)-5-bromo-7-methyl-3,5-octadien-2-yl]-tetrahydro-1H-pyrrol-2yl) methanol (6) and (1-(2S)-[(2S)(3E,5Z)-5-bromo-7-methyl-3, 5-octadien-2-yl] tetrahydro-1H-pyrrol-2-yl) methanol 7) were formed in a 65:35 ratio from 3-bromo-5-ethyl-2-isopropylthiophene, 1,1-dioxide (5) and L-prolinol. (5R,5aS,8R,9R,9aS,9bS)-Ethyl 7-bromo-8-isopropyl-5-methyl-2,3 ,5,5a,8,9,9a,9b-octahydro-1H-pyrrolo[2,1-a] isoindole-9-carboxylate (10) and (5S,5aS,8R,9R,9aS,9bS)-ethyl 7-bromo-8-isopropyl-5-methyl-2,3,5,5a,8, octahydro-1H-pyrrolo[2,1-a]isoindole-9-carboxylate (12) were synthesized from 6 and 7 in order to establish the absolute configuration of the ring-opened products. The asymmetric induction at C(2) in the ring-opened products can be explained by the preferential formation of E tautomers over Z tautomers and the preferential formation of the E(2S) (15) and Z(2S) (17) enantiomers over the E(2R) (14) and Z(2R) (16) enantiomers when 5 tautomerizes. The tautomers form complexes with the L-prolinol dimers, and the enantiotopic face that will preferentially be attacked by another L-prolinol equivalent in a Michael addition will be the one anti to the dimer and syn to the isopropyl group. (Less)
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published
subject
in
Acta Chemica Scandinavica
volume
52
issue
5
pages
533 - 540
publisher
Munksgaard International Publishers
external identifiers
  • scopus:0009321573
ISSN
0904-213X
language
English
LU publication?
yes
id
bfa1dc25-aa2d-4cfa-bf77-acf4a2668e81 (old id 33200)
date added to LUP
2007-06-19 14:36:54
date last changed
2017-01-01 07:27:50
@article{bfa1dc25-aa2d-4cfa-bf77-acf4a2668e81,
  abstract     = {The diastereomers (1-(2S)-[(2R) (3E,5Z)-5-bromo-7-methyl-3,5-octadien-2-yl]-tetrahydro-1H-pyrrol-2yl) methanol (6) and (1-(2S)-[(2S)(3E,5Z)-5-bromo-7-methyl-3, 5-octadien-2-yl] tetrahydro-1H-pyrrol-2-yl) methanol 7) were formed in a 65:35 ratio from 3-bromo-5-ethyl-2-isopropylthiophene, 1,1-dioxide (5) and L-prolinol. (5R,5aS,8R,9R,9aS,9bS)-Ethyl 7-bromo-8-isopropyl-5-methyl-2,3 ,5,5a,8,9,9a,9b-octahydro-1H-pyrrolo[2,1-a] isoindole-9-carboxylate (10) and (5S,5aS,8R,9R,9aS,9bS)-ethyl 7-bromo-8-isopropyl-5-methyl-2,3,5,5a,8, octahydro-1H-pyrrolo[2,1-a]isoindole-9-carboxylate (12) were synthesized from 6 and 7 in order to establish the absolute configuration of the ring-opened products. The asymmetric induction at C(2) in the ring-opened products can be explained by the preferential formation of E tautomers over Z tautomers and the preferential formation of the E(2S) (15) and Z(2S) (17) enantiomers over the E(2R) (14) and Z(2R) (16) enantiomers when 5 tautomerizes. The tautomers form complexes with the L-prolinol dimers, and the enantiotopic face that will preferentially be attacked by another L-prolinol equivalent in a Michael addition will be the one anti to the dimer and syn to the isopropyl group.},
  author       = {Tsirk, Anders and Gronowitz, Salo and Hörnfeldt, Anna-Britta},
  issn         = {0904-213X},
  language     = {eng},
  number       = {5},
  pages        = {533--540},
  publisher    = {Munksgaard International Publishers},
  series       = {Acta Chemica Scandinavica},
  title        = {Asymmetric Induction in the Amine Induced Ring-Opening of 3-Bromo-5-ethyl-2-isopropylthiophene-1,1-dioxide Using L-Prolinol},
  volume       = {52},
  year         = {1998},
}