Zirconocene mediated synthesis of nitrogen heterocycles
Zirconocene mediated synthesis of nitrogen heterocycles
4-Aza-1,7-octa-dienes, -enynes, ynenes and -diynes have been cyclised using Cp2Ar-(1-butene). The resultant 3-aza-8-zirconabicyclo[4.3.0]non-anes,-6-enes, -9-enes and -6,9-dienes were quenched with either MeOH, I2 or CO to generate a range of products containing a 3,4-disubstituted piperidine structure. Where the bicyclisation resulted in a mixture of diastereomers, the effects of temperature on the ratio of the two zirconabicycles was studied. The conjugated exocyclic dienes formed from 4-aza-1,7-octadiynes were reacted with activated dienophiles to yield reduced isoquinolines.
New methods have been developed for the bicyclisation of substrates containing hindered alkene and terminal alkyne groups using Cp2Zr(DMAP)2 and Cp2Zr-(C2H4) respectively. The latter reagent was employed in the reductive coupling of but-2-enyl-methyl-(2-methyl-but-3-ynyl)-amine, the key step in our synthesis of (+/-)-tecomanine.
2-Aza-7-zirconabicyclo[3.3.0]oct-anes, -5-enes, -8-enes and -5,8-dienes have been prepared by the unprecedented bicyclisation of substrates containing enamine and ynamine functionalities. The latter three complexes have been isolated and characterised using NMR techniques. 'Work-up' of these zirconabicycles with MeOH, Br2, Co and xylylisocyanide generated a range of 2,3-disubstituted pyrrolidines, with the occasional formation of 2o amine by-products.
The novel Cp2Zr-(1-butene) mediated bicyclisation of 3-oxo-1,6-heptynenes has been exemplified using two substrates. The resultant complexes were protonated to form 2-alkylidene-3-methyl-tetrahydrofurans in good yield.
University of Southampton
1996
Kemp, Mark Ian
(1996)
Zirconocene mediated synthesis of nitrogen heterocycles.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
4-Aza-1,7-octa-dienes, -enynes, ynenes and -diynes have been cyclised using Cp2Ar-(1-butene). The resultant 3-aza-8-zirconabicyclo[4.3.0]non-anes,-6-enes, -9-enes and -6,9-dienes were quenched with either MeOH, I2 or CO to generate a range of products containing a 3,4-disubstituted piperidine structure. Where the bicyclisation resulted in a mixture of diastereomers, the effects of temperature on the ratio of the two zirconabicycles was studied. The conjugated exocyclic dienes formed from 4-aza-1,7-octadiynes were reacted with activated dienophiles to yield reduced isoquinolines.
New methods have been developed for the bicyclisation of substrates containing hindered alkene and terminal alkyne groups using Cp2Zr(DMAP)2 and Cp2Zr-(C2H4) respectively. The latter reagent was employed in the reductive coupling of but-2-enyl-methyl-(2-methyl-but-3-ynyl)-amine, the key step in our synthesis of (+/-)-tecomanine.
2-Aza-7-zirconabicyclo[3.3.0]oct-anes, -5-enes, -8-enes and -5,8-dienes have been prepared by the unprecedented bicyclisation of substrates containing enamine and ynamine functionalities. The latter three complexes have been isolated and characterised using NMR techniques. 'Work-up' of these zirconabicycles with MeOH, Br2, Co and xylylisocyanide generated a range of 2,3-disubstituted pyrrolidines, with the occasional formation of 2o amine by-products.
The novel Cp2Zr-(1-butene) mediated bicyclisation of 3-oxo-1,6-heptynenes has been exemplified using two substrates. The resultant complexes were protonated to form 2-alkylidene-3-methyl-tetrahydrofurans in good yield.
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Published date: 1996
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Local EPrints ID: 459837
URI: http://eprints.soton.ac.uk/id/eprint/459837
PURE UUID: 65f5dd2b-fd54-44fc-8770-ddb663fa317a
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Date deposited: 04 Jul 2022 17:19
Last modified: 04 Jul 2022 17:19
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Author:
Mark Ian Kemp
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