3-carbonyl-3H-indole: Direct observation and tetramerization to a tetrabenzoporphyrin analogue

Abstract

Heterocyclic ketenes with α-nitrogen atoms such as 2-carbonyl-2H-indole (6) dimerize to a pyrazinedione type molecule (7). However, the β-nitrogen analogue, viz. 3-carbonyl-3H-indole (5) oligomerizes to tetramer 4. The direct observation of ketene 5 and the characterization of tetramer 4 are described. © 1995.