Intramolecular addition of carbon radicals to aldehydes: synthesis of enantiopure tetrahydrofuran-3-ols
摘要:
A simple and efficient substrate-controlled asymmetric synthesis of enantiopure tetrahydrofuran-3-ols by a 5-exo-trig radical cyclization is described. This cyclization occurs when a delta-carbon radical adds intramolecularly to the carbonyl group of an aldehyde. The delta-carbon radicals can be efficiently produced from the tin hydride mediated deselenenylation of 5-phenylseleno-3-oxapentanals, which were easily prepared starting from commercially available enantiopure epoxides or chlorohydrins. (c) 2007 Elsevier Ltd. All rights reserved.
Intramolecular addition of carbon radicals to aldehydes: synthesis of enantiopure tetrahydrofuran-3-ols
摘要:
A simple and efficient substrate-controlled asymmetric synthesis of enantiopure tetrahydrofuran-3-ols by a 5-exo-trig radical cyclization is described. This cyclization occurs when a delta-carbon radical adds intramolecularly to the carbonyl group of an aldehyde. The delta-carbon radicals can be efficiently produced from the tin hydride mediated deselenenylation of 5-phenylseleno-3-oxapentanals, which were easily prepared starting from commercially available enantiopure epoxides or chlorohydrins. (c) 2007 Elsevier Ltd. All rights reserved.
Ring-Closure Reactions through Intramolecular Displacement of the Phenylselenonyl Group by Nitrogen Nucleophiles: A New Stereospecific Synthesis ofN-Tosyl andN-Benzoyl-1,3-oxazolidin-2-ones fromβ-Hydroxyalkyl Phenyl Selenides
3-oxazolidin-2-ones from the easily available beta-hydroxyalkyl phenyl selenides is presented. After transformation into the N-tosyl or N-benzoyl carbamates, the selenides were oxidized to the corresponding selenones. The key step of the process is the ring-closure reaction, which occurs by stereospecific intramolecular nucleophilic substitution of the selenonegroup by the nitrogen atom of the carbamate. Enantiomerically
The enantioselective chalcogeno-Baylis-Hillman reaction was investigated by the use of chiral hydroxy chalcogenides in the presence of TiCl4 under atmospheric pressure. The best result was obtained with 10-methylthioisobornenol as a chiral hydroxy chalcogenide.
pure epoxides, enantiomerically pure substituted tetrahydrofurans were prepared using simple conversions promoted by organoseleniumreagents. The first step consisted in the opening of the epoxides with phenylselenolate anions to afford hydroxyalkyl phenyl selenides. The PhSe group was then substituted by an allyl group by treatment with allyltributyltin and AIBN. The reaction of these allylic derivatives
Lipase-catalyzed resolution of β-hydroxy selenides
作者:Michelangelo Gruttadauria、Paolo Lo Meo、Serena Riela、Francesca D’Anna、Renato Noto
DOI:10.1016/j.tetasy.2006.10.010
日期:2006.10
Eleven beta-hydroxy selenides were kinetically resolved using an immobilized lipase (Amano PS-C II) in toluene in the presence of vinyl acetate at 30 degrees C. This approach provided, in several cases, both enantiomers in high enantiomeric excess. The role of the size of substituents and the behaviour of cyclic beta-hydroxy selenides is also discussed. Enantiopure beta-hydroxy selenides are useful building blocks. As an application of this chemistry, enantiopure (1S,2R)-indene oxide was obtained in one step from the proper enantiopure beta-hydroxy selenide. (c) 2006 Published by Elsevier Ltd.