186597-31-9Relevant academic research and scientific papers
Regio- and stereoselective 5-exo radical cyclizations on a chiral perhydro-1,3-benzoxazine moiety. An access to enantiopure 3-alkylpyrrolidines
Andres, Celia,Duque-Soladana, Juan P.,Pedrosa, Rafael
, p. 4273 - 4281 (2007/10/03)
Both enantiomers of chiral, nonracemic 3-alkyl-substituted pyrolidines are prepared by diastereo-selective 5-exo-trig cyclization on (-)-8- aminomenthol-derived perhydro-1,3-benzoxazines used as chiral auxiliaries, followed by elimination of the menthol appendage. The diastereoselective radical cyclization is promoted by tributyltin hydride and occurs on a 3- aza-5-hexenyl-type radical, leading to five-membered rings in high yield. The stereocontrol of the cyclization is strongly influenced by 1,3-allylic strain so that an appropriate substitution pattern on the olefin-acceptor and the presence of a vicinal stereocenter are crucial for achieving good diastereoselectivity. The enantiopure pyrrolidines are obtained in three steps with concomitant recovering of the starting (+)-pulegone auxiliary.
A novel approach to chiral, nonracemic pyrrolidines by 5-exo-trig diastereoselective radical cyclization on acrylamides derived from (-)-8- aminomenthol
Andres, Celia,Duque-Soladana, Juan P.,Pedrosa, Rafael
, p. 4282 - 4288 (2007/10/03)
α,β-Unsaturated amides supported on perhydro-1,3-benzoxazines derived from (-)-8-aminomenthol as chiral auxiliaries undergo regio- and stereoselective 5-exo-trig radical cyclization leading to diastereomeric five-membered lactams. These cyclization products are transformed into enantiopure 3,4-disubstituted pyrrolidines by reduction with aluminum hydride followed by removal of the menthol appendage.
Diastereoselective 5-exo-trig radical cyclisation on N-acryloyl-tetrahydro-1,3-oxazines. A novel approach to enantiopure 3-substituted pyrrolidines
Andres, Celia,Duque-Soladana, J. Pablo,Iglesias, Jesus M.,Pedrosa, Rafael
, p. 9085 - 9086 (2007/10/03)
N-acryloyl-2-(phenylselenomethyl)-tetrahydro-1,3-oxazine 1 generates a carbon-centred radical in the presence of tri-n-butyltin hydride and AIBN. This radical underwent diastereoselective 5-exo-trig cyclisation leading to a mixture of five-membered lactams 2a and 2b (d.e. 68%). Chromatographic separation of the diastereomers and elimination of the chiral auxiliary provided enantiopure (R)-3-methylpyrrolidine in good chemical yield. Copyright (C) 1996 Elsevier Science Ltd.
