Stereoselective synthesis of 5-alkyliden-6-aminotetrahydro-2-pyranones through an unexpected isomerization of the hydroxytetrahydro-2-pyridinones obtained by the selective reduction of acylated enaminones
摘要:
A convenient methodology for the stereoselective preparation of 5-alkyliden-6-aminotetrahydro-2-pyranone 4 is reported. The synthesis of 2-pyranone 4 occurs through an unknown isomerization mechanism of the hydroxytetrahydro-2-pyridinone 3, an accessible starling material obtained by mild and selective reduction of the 5-acyltetrahydro-2-pyridinone 2. The isomerization mechanism and the stereoselectivity in the synthesis of 2-pyranone 4 was investigated and rationalized. (C) 1997 Elsevier Science Ltd. All rights reserved.
Heterocycle Formation through Aza-Annulation: Stereochemically Controlled Syntheses of (.+-.)-5-Epitashiromine and (.+-.)-Tashiromine
摘要:
N-alkylenamines, stabilized through conjugation with an electron-withdrawing group, undergo aza-annulation with acryloyl chloride to provide a convergent route for the construction of six-membered nitrogen heterocycles. In addition to enhancing the C-alkylation process of annulation relative to the competing N-acylation process, the electron withdrawing substituent controlled the regioselectivity of alkene formation in both the intermediate enamine and in the unsaturated lactam product. A variety of functional groups, which include -COMe, -COPh, -CO(2)R, -CONHPh, -CN, -P(O)(OEt)(2), and -SO(2)Ph, were used to determine the effect of the electron-withdrawing substituents upon both the annulation reaction with acryloyl chloride and the subsequent hydrogenation process. When the enamide annulation product was stabilized through conjugation with ester or amide substituents, catalytic hydrogenation of the ate-annulation product resulted in the formation of vicinal stereocenters with high cis selectivity. The utility of this methodology was demonstrated by application of the condensation/aza-annulation/hydrogenation sequence as the key for construction and stereochemical control of the indolizidine ring system of (+/-)-tashiromine.
“Conformationally restricted β-amino acid isosteres prepared through regioselectively controlled aza-annulation.”
作者:K. Paulvannan、John R. Stille
DOI:10.1016/s0040-4039(00)61389-8
日期:1993.12
A variety of electron withdrawing substituents were used to enhance the aza-annulation of enamines with acryloyl chloride, to direct the regioselectivity of alkene formation, and to facilitate hydrogenation of the unsaturated annulation product. The resulting δ-lactam products were β-amino acid analogs with structural features similar to those of established peptide isosteres.
Heterocycle Formation through Aza-Annulation: Stereochemically Controlled Syntheses of (.+-.)-5-Epitashiromine and (.+-.)-Tashiromine
作者:K. Paulvannan、John R. Stille
DOI:10.1021/jo00086a009
日期:1994.4
N-alkylenamines, stabilized through conjugation with an electron-withdrawing group, undergo aza-annulation with acryloyl chloride to provide a convergent route for the construction of six-membered nitrogen heterocycles. In addition to enhancing the C-alkylation process of annulation relative to the competing N-acylation process, the electron withdrawing substituent controlled the regioselectivity of alkene formation in both the intermediate enamine and in the unsaturated lactam product. A variety of functional groups, which include -COMe, -COPh, -CO(2)R, -CONHPh, -CN, -P(O)(OEt)(2), and -SO(2)Ph, were used to determine the effect of the electron-withdrawing substituents upon both the annulation reaction with acryloyl chloride and the subsequent hydrogenation process. When the enamide annulation product was stabilized through conjugation with ester or amide substituents, catalytic hydrogenation of the ate-annulation product resulted in the formation of vicinal stereocenters with high cis selectivity. The utility of this methodology was demonstrated by application of the condensation/aza-annulation/hydrogenation sequence as the key for construction and stereochemical control of the indolizidine ring system of (+/-)-tashiromine.
Stereoselective synthesis of 5-alkyliden-6-aminotetrahydro-2-pyranones through an unexpected isomerization of the hydroxytetrahydro-2-pyridinones obtained by the selective reduction of acylated enaminones
作者:Cristina Cimarelli、Gianni Palmieri
DOI:10.1016/s0040-4020(97)10333-7
日期:1998.1
A convenient methodology for the stereoselective preparation of 5-alkyliden-6-aminotetrahydro-2-pyranone 4 is reported. The synthesis of 2-pyranone 4 occurs through an unknown isomerization mechanism of the hydroxytetrahydro-2-pyridinone 3, an accessible starling material obtained by mild and selective reduction of the 5-acyltetrahydro-2-pyridinone 2. The isomerization mechanism and the stereoselectivity in the synthesis of 2-pyranone 4 was investigated and rationalized. (C) 1997 Elsevier Science Ltd. All rights reserved.