Diastereoselective Lewis acid-catalysed [4+2] cycloadditions of 3-alkyl-, 3-aryl- and 3-carboxyl-2H-azirines: a route to aziridine containing azabicyclo[4.1.0]heptanes and azatricyclo[2.2.1.0]nonanes
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- 作者：Ray ; Colin A. ; Risberg ; Erik ; Somfai ; Peter
- 关键词：azirine ; aziridine ; hetero Diels&ndash ; Alder reaction
- 刊名：Tetrahedron
- 出版年：2002
- 出版时间：July 22, 2002
- 年：2002
- 卷：58
- 期：30
- 页码：5983-5987
- 全文大小：96.0 K
文摘
3-Substituted-2H-azirines have been employed as 2π components in Lewis acid-catalysed hetero Diels–Alder reactions with a variety of diene systems. A series of Lewis acids were screened for catalytic behaviour in the reaction between Danishefsky's diene and 3-phenyl-2H-azirine to give the cycloaddition adduct, and in most cases elevated temperature were required to effect cycloaddition. A noteworthy exception was a BF3·Et2O-catalysed cycloaddition which proceeded in less than 1h between −70°C and −60°C. The cycloadditions were found to proceed with endo selectivity providing a single diastereoisomeric product. Benzyl 2H-azirine-3-carboxylates were found to be activated by Lewis acids and participate in endo selective cycloadditions at −20°C.