- Intramolecular sulfur-assisted NaBH4 reduction of esters synthesis of 5-oxo-ETE and 5-oxo-12-HETE
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Ester groups are reduced very efficiently in sulfur-containing molecules situated at close proximity to the ester group. We have used this procedure to regioselectively, efficiently and in high yield reduce an ester group in the presence of another ester group further removed from the sulfur atom. (C) 2000 Elsevier Science Ltd.
- Khanapure, Subhash P.,Saha, Goutam,Sivendran, Sashikala,Powell, William S.,Rokach, Joshua
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p. 5653 - 5657
(2007/10/03)
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- (1R,3R)-2-Methylene-1,3-dithiolane 1,3-dioxide: A highly reactive and highly selective chiral ketene equivalent in cycloaddition reactions with a broad range of dienes
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The chiral ketene equivalent trans-2-methylene-1,3-dithiolane 1,3-dioxide has been prepared in racemic and enantiomerically pure form in four steps. The key step in the asymmetric synthesis utilised a Modena asymmetric oxidation of 2-benzyloxymethyl-1,3-dithiolane which gave the trans bis-sulfoxide with high diastereocontrol (91:9 in favour of trans) and high enantiocontrol (>97% ee). The ketene equivalent shows high selectivity (>97:3) in Diels-Alder reactions with a range of simple dienes (cyclopentadiene, furan, 1-methoxybutadiene, Danishefsky's diene, 1-methoxycyclohexa-1,3-diene) and shows high reactivity as it is able to undergo cycloadditions with notoriously unreactive dienes (cyclohexa-1,3-diene, 90:10 selectivity; 2H-pyran-2-one, 94:6 selectivity). Dihydropyridines also participated in cycloaddition reaction but with only moderate selectivity (73:27). The Diels-Alder adducts can be readily deprotected to return the carbonyl group using a two step sequence involving reduction followed by hydrolysis.
- Aggarwal, Varinder K.,Gueltekin, Zeynep,Grainger, Richard S.,Adams, Harry,Spargo, Peter L.
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p. 2771 - 2781
(2007/10/03)
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- CHIRAL KETENE EQUIVALENTS FOR USE IN ASYMMETRIC SYNTHESIS
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Trans-1,3-dithiolane-1,3-dioxide is a more reactive and more selective chiral ketene equivalent than trans-1,3-dithiane-1,3-dioxide.
- Aggarwal, Varinder K.,Lightowler, Mark
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p. 407 - 408
(2007/10/02)
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- SYNTHESIS AND PROPERTIES OF SOME O--GLYCOLALDEHYDES
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O-glycolaldehydes (1a-e; alkyl = Et, Pr, Pri, But, and -CH2-, respectively) have been prepared from the corresponding O-glycolaldehyde dimethyl acetals (2a-e) by acid hydrolysis.In anhydrous 1,4-dioxane in the presence of BF3*(Et2O)2, 1a-c were partially transformed into glycolaldehyde bis(dialkyl dithioacetals), 1d afforded trans-2,6-bis(tert-butylthio)-1,4-dioxane and 3,5-bis(tert-butylthio)-1,4-oxathiane, and 1e did not react.The acetals 2a-e were prepared from the appropriate glycolaldehyde dialkyl dithioacetal by O-alkylation with bromoacetaldehyde dimethyl acetal.
- Aparicio, F. J. Lopez,Benitez, F. Zorrilla,Gonzalez, F. Santoyo
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p. 287 - 296
(2007/10/02)
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