Convergence of products from Povarov and von Miller reactions: approaches to helquinoline |
| |
Authors: | Paul J. Stevenson Peizhao HeBrian Daly |
| |
Affiliation: | School of Chemistry and Chemical Engineering, Queens University, Belfast, BT9 5AG, N. Ireland, UK |
| |
Abstract: | Yttrium triflate or triflic acid catalysed Povarov reaction of methyl anthranilate with ethyl vinyl ether, both as aldehyde surrogate and as alkene, gave the desired 2-methyl-4-ethoxytetrahydroquinoline diastereoisomers as the major products along with four component coupling von Miller adducts. A proton NMR-study, using yttrium triflate as catalyst, revealed that the cis-diastereoisomers were the initial major products in both the Povarov and von Miller reactions but that these isomerised to the trans-diastereoisomers under the reaction conditions. Two distinct pathways for forming von Miller adducts were uncovered with the initial Povarov products being converted to von Miller adducts under the reaction conditions. Replacement of the 4-ethoxy with a 4-methoxy group under acidic conditions gave predominantly the trans-diastereoisomer, which was subsequently converted to a cis/trans mixture of the tetrahydroquinoline antibiotic helquinoline. It was also possible to convert the von Miller products to Povarov products under acidic conditions. |
| |
Keywords: | Povarov reaction Von Miller reaction Lewis acid catalysis Helquinoline Multi-component coupling Alkaloid |
本文献已被 ScienceDirect 等数据库收录! |
|