| Title: |
From alpha,beta-unsaturated Fischer carbene complexes to highly substituted 3-ethoxycyclopentadienes, masked cyclopentenones |
| Authors: |
Wu, Y.; Flynn, B.; Schirmer, H.; Funke, Frank; Mueller, S.; Labahn, T.; Notzel, M.; de Meijere, Armin |
| Contributors: |
Wu, Y.; Flynn, B.; Schirmer, H.; Funke, Frank; Mueller, S.; Labahn, T.; Notzel, M.; de Meijere, Armin |
| Publisher Information: |
Wiley-v C H Verlag Gmbh |
| Publication Year: |
2004 |
| Collection: |
Georg-August-Universität Göttingen: GoeScholar |
| Description: |
The beta-amino-substituted mu,beta-unsaturated Fischer carbene complexes 3 are readily available by a four step one-pot procedure from terminal alkynes, chromium hexacarbonyl and secondary amines (24 examples with yields of 68-99% and 7 examples with yields of 26-63%). The formal [3+2] cycloadditions of complexes 3 with different alkynes including diynes and enynes performed in donor solvents such as pyridine or acetonitrile afforded highly substituted 5-(dialkylamino)-3-ethoxycyclopentadienes 7, generally in medium to excellent yields (25 examples with yields of 60-95% and 7 examples with yields of 18-53%). The steric and electronic effects of the substituents on the carbene complexes and the incorporated alkynes on the regio- and stereo selectivity of the ring-forming reaction have been elaborated. An interesting 1,5- or, more likely, 1,2-migration of the dimethylamino group was observed for 5-(dimethylamino)-3-ethoxycyclopentadienes with trimethylsilyl and jPr substituents at C-5. Attempted asymmetric syntheses of cyclopentadienes 7 from complexes 3 with chiral amino groups or substituents were only moderately successful. At a center of chirality in the secondary amino group, complexes of type 3 gave compounds 7 with diastereomeric excesses of, at best, 59% in yields of 54%, and with a stereogenic center in the substituent R-1 attached to the vinyl group of 3, diastereomeric excesses as high as 94% could be achieved, but with poor chemical yields (21%). In general, cyclopentenones 21 could be easily obtained from the cyclopentadienes 7 under acidic conditions in very good yields (4 examples with yields of 81-98%, 1 example with an overall yield of 50% from complex 3). Intramolecular aldol reactions of dicarbonyl compounds generated by hydrolysis of cyclopentadienes 7 with acetal-protected aldehyde or ketone carbonyl groups in either the 5-substituent R-1 or the N-substituent R-2 led to the bicyclic compounds 22 and 23. The dimethylamino group in cyclopentenones 21 could be either eliminated or transformed ... |
| Document Type: |
article in journal/newspaper |
| Language: |
unknown |
| Relation: |
000189310700007 |
| DOI: |
10.1002/ejoc.200300534 |
| Availability: |
https://resolver.sub.uni-goettingen.de/purl?gro-2/48821; https://doi.org/10.1002/ejoc.200300534 |
| Rights: |
info:eu-repo/semantics/openAccess |
| Accession Number: |
edsbas.459D78D3 |
| Database: |
BASE |