I. Three-Component Coupling Reactions of Methyl Thiophenecarboxylate with Heterocyclic Methyl Ketones II. A Study of Enantioselective Aldol-Tishchenko Reactions
碩士 === 國立臺灣大學 === 化學研究所 === 87 === The first part of this thesis reports the SmI2/HMPA promoted coupling reactions of methyl thiophene2-carboxylate with heterocyclic methyl ketones. Methyl thiophene2-carboxylate underwent such reductive double electrophilic reactions with 2 equivalents of...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
1999
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| Online Access: | http://ndltd.ncl.edu.tw/handle/31709022855176283500 |
| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 87 === The first part of this thesis reports the SmI2/HMPA promoted coupling reactions of methyl thiophene2-carboxylate with heterocyclic methyl ketones. Methyl thiophene2-carboxylate underwent such reductive double electrophilic reactions with 2 equivalents of carbonyl compounds to give disubstituted 4,5-dihydrothoiphene-2-carboxylates in high regio- and diastereoselectivity. The coupling products were then converted to a series of thiophene-fused benzo[b]thiophenes containing additional heterocycles, via acid-catalyzed dehydration and sequential oxidation-electrocyclization-oxidation on treatment with DDQ. These heterocyclic compounds with long p-conjugated system showed the UV absorptions near 300nm and the fluorescence near 400nm.
The second part of this thesis describes the catalytic asymmetric tadem aldol-Tishchenko reactions between ketons and aldehydes. We used Sm2+ or Sm3+ ions as the Lewis acids and various chiral ligands as chiral auxillaries to promote such reactions. We examined the reactions in many reaction conditions to enhance the yields and enantioselectivities. So far, the aldol-Tishchenko reaction of acetophenone and benzaldehyde was realized by using SmI2/n-BuLi/(R)-BINOL as the catalyst to give 10 in 12% yield and 69%ee.
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