Stereoselectivity in the reduction of chiral indoles to indolines
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The reduction of 2-alkylindoles containing a chiral substituent at the nitrogen atom by sodium cyanoborohydride in an acidic medium at -80°C is accompanied by the formation of indolines with S-configuration of the new chiral site at C(2). An AMI quantum chemical calculation showed that the major diastereomer has greater thermodynamic stability. However, the high diastereoselectivity of this reduction may be attributed only to the relative stability of the different conformations of the intermediate indoleninium cations leading to different diastereomers.
KeywordsNitrogen Sodium Organic Chemistry Nitrogen Atom Indole
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