Synthesis of 1,2,3,4‐tetrahydrocarbazole‐9a‐¹³C and carbazole‐9a‐¹³C

Abstract

SUMMARYThe synthesis of 1,2,3,4-tetrahydrocarbamle-9a-13C and carbazole9a-13C via cyclohexanone-l-13C, prepared in turn from carbon dioxide-13C and 1,5-pentanedimagnesium bromide is described.Key Words: 1,2,3,4-tetrahydrocarbazole-9a-13C, carbazole-9a-l3C, ~yclohexanone-l-~3C, 1,5-pentanedimagnesium bromide, carbon dioxide-13C. INTRODUC'IIONIn earlier publicatisns (1) we described the synthesis of several 13C-labeled compounds (2) for use in studies on the effectiveness of hydrogen transfer solvents in coal liquification processes.Since nitrogen heterocyclic compounds are abundant in coal liquids and because their presence can influence the hydrogen transfer process, the study of 13C-labeled heterocyclic compounds is an obvious extension in gaining a better understanding of the coal liquification process (3).In this paper we describe the preparation of the specifically labeled title compounds synthesized from cyclohexanone-l-13C (1) as shown in Scheme I.

Synthetic approaches to regiospecifically mono‐ and dilabelled arenes

“…The subsequent aromatisation was carried out at 320°C and gave an overall 7% yield of [1‐ 14 C]dimethylphenol, which was further elaborated by nitrosation and reductive alkylation 38. Later workers were able to carry out the preparation of [ 13 C]cyclohexanone in 24–38% yield using the same approach but without the need to heat the mixture,39 and a further improvement has been reported, providing [ 14 C]cyclohexanone in 40–60% yield 40. Further development could enable this to become an economical phenol synthesis.…”