Stereocontrolled conjugate additions to dihydroindolizinone systems. Synthesis of enantiopure polysubstituted tetrahydropyrrolo[2,1-a]isoquinolones
摘要:
Conjugate addition reactions of various types of nucleophiles to the gamma-lactam unit of dihydroindolizinone systems have been studied. The addition of cuprates, amines or stabilized carbanions requires the activation of the unsaturated bicyclic lactam with a EWG at C-2, while sulfur-stabilized carbanions are reactive enough to add to the unsubstituted lactam. The stereochemical outcome of the conjugate addition reaction depends on the nature of the substituent at the angular position, and the incoming nucleophile. Thus 1,10b-cis or 1,10b-trans diastereomers could be obtained selectively with dr>95:5. The tandem conjugate addition-alkylation also takes place in good yields. These reactions have been applied to the synthesis of enantiopure tetrahydropyrrolo [2,1-a]isoquinolines. (C) 2009 Elsevier Ltd. All rights reserved.
Stereocontrolled conjugate additions to dihydroindolizinone systems. Synthesis of enantiopure polysubstituted tetrahydropyrrolo[2,1-a]isoquinolones
摘要:
Conjugate addition reactions of various types of nucleophiles to the gamma-lactam unit of dihydroindolizinone systems have been studied. The addition of cuprates, amines or stabilized carbanions requires the activation of the unsaturated bicyclic lactam with a EWG at C-2, while sulfur-stabilized carbanions are reactive enough to add to the unsubstituted lactam. The stereochemical outcome of the conjugate addition reaction depends on the nature of the substituent at the angular position, and the incoming nucleophile. Thus 1,10b-cis or 1,10b-trans diastereomers could be obtained selectively with dr>95:5. The tandem conjugate addition-alkylation also takes place in good yields. These reactions have been applied to the synthesis of enantiopure tetrahydropyrrolo [2,1-a]isoquinolines. (C) 2009 Elsevier Ltd. All rights reserved.
The stereoselectivity of the conjugate addition of carbon nucleophiles to the bicyclic γ-lactam unit of dihydropyrrolo[2,1- a]isoquinolones depends on the nature of the nucleophile and the substituent at the angular position.
Conjugate addition reactions of various types of nucleophiles to the gamma-lactam unit of dihydroindolizinone systems have been studied. The addition of cuprates, amines or stabilized carbanions requires the activation of the unsaturated bicyclic lactam with a EWG at C-2, while sulfur-stabilized carbanions are reactive enough to add to the unsubstituted lactam. The stereochemical outcome of the conjugate addition reaction depends on the nature of the substituent at the angular position, and the incoming nucleophile. Thus 1,10b-cis or 1,10b-trans diastereomers could be obtained selectively with dr>95:5. The tandem conjugate addition-alkylation also takes place in good yields. These reactions have been applied to the synthesis of enantiopure tetrahydropyrrolo [2,1-a]isoquinolines. (C) 2009 Elsevier Ltd. All rights reserved.