- Organocatalytic asymmetric formal [3 + 2] cycloaddition with in situ-generated N-carbamoyl nitrones
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(Chemical Equation Presented) A novel organocatalytic formal [3 + 2] cycloaddition reaction with in situ generation of N-carbamoyl nitrones is presented. For the first time, N-Boc- and N-Cbz-protected isoxazolidines have been directly obtained as single diastereoisomers in generally high yields and enantiomeric excesses using mild reaction conditions and inexpensive, readily available Cinchona alkaloid quaternary ammonium salts as catalysts. Synthetic manipulations of the products provided highly valuable building blocks such as free isoxazolidines, a N-Boc-1,3-aminoalcohol, and a free δ-lactam. This report represents a pioneering work in the use of N-carbamoyl nitrones as electron-poor 1,3-dipoles and glutaconates as new dipolarophiles in asymmetric catalysis.
- Gioia, Claudio,Fini, Francesco,Mazzanti, Andrea,Bernardi, Luca,Ricci, Alfredo
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supporting information; experimental part
p. 9614 - 9615
(2011/02/23)
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- The Structure of Glutaconic Anhydride and the Synthetic Utility of its Diels-Alder Adduct with Cyclopentadiene
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In non-polar solvents glutaconic anhydride exists predominantly as its dioxo-tautomer (1).Diels-Alder reaction with cyclopentadiene affords 3-endo-carboxynorborn-5-en-2-endo-ylacetic acid anhydride (5) having considerable synthetic potential, and which on hydrolysis gives the corresponding bis-endo-dicarboxylic acid (6a).The dimethyl ester of (6a) may be epimerised and hydrolysed to the trans-dicarboxylic acid, 3-exo-carboxynorborn-5-en-2-endo-ylacetic acid (9a).The acids (6a) and (9a) have been characterised as a γ-iodolactone (7a) and a δ-iodolactone (13), respectively.
- Briggs, Stuart P.,Davies, David I.,Newton, Roger F.,Reynolds, Derek P.
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p. 146 - 149
(2007/10/02)
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