Zinc Salt Promoted Diastereoselective Synthesis of Chiral Propargylamines Using Chiral Piperazines and Their Enantioselective Conversion into Chiral Allenes

Autor:	Bantu Udaykumar, Manasi Dalai, Polimera Obula Reddy, Laxman M. Alakonda, Mariappan Periasamy, Athukuri Edukondalu
Rok vydání:	2014
Předmět:	Allene Organic Chemistry Imine Enantioselective synthesis chemistry.chemical_element Zinc Catalysis Piperazine chemistry.chemical_compound chemistry Organic chemistry Physical and Theoretical Chemistry Chirality (chemistry) Zinc bromide
Zdroj:	European Journal of Organic Chemistry. 2014:6067-6076
ISSN:	1434-193X
Popis:	Zinc chloride catalyzed reactions of chiral piperazine derivatives 4a–d with 1-alkynes and aldehydes give chiral propargylamines in 67–95 % yields with up to 99:1 dr. The chiral propargylamines are converted into chiral allenes by using zinc bromide in short reaction times (1–2 h) in high enantioselectivities (up to 99 % ee) in good yields (up to 89 %). The chiral piperazines are recovered in good yields (79–86 %) by reduction of the imine byproducts in situ by using NaBH4. Unexpectedly, the chiral aryl-substituted allenes undergo facile cyclodimerization under neat conditions at 25 °C, in contrast to an earlier report that cyclodimerization takes place at 80 °C in benzene, which further illustrates the importance of the two-step procedure reported herein because the chiral propargylamine may be converted into chiral allene when required.
Databáze:	OpenAIRE
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