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Paper | Regular issue | Vol 78, No. 10, 2009, pp.2467-2475
Published online, 3rd June, 2009
DOI: 10.3987/COM-09-11744
Reactions of Ninhydrin with Benzo[b]thiophenes

Nono Suzue, Rie Ishii, Ryo Kamiya, Hidetsugu Wakabayashi, and Keiji Kobayashi*

*Department of Chemistry, Faculty of Science, Josai University, 1-1 Keyakidai, Sakado, Saitama 350-0295, Japan


The reaction of ninhydrin with benzo[b]thiophene in acetic acid in the presence of a small amount of sulfuric acid afforded a novel fluorenone compound fused to benzo[b]thiophene rings. In the reaction using 2,2’-bibenzo[b]thiophene, phthalide conjoined in a spiro framework was unexpectedly isolated along with an isocoumarin derivative which is fused to benzo[b]thiophene and benzene rings. The product related to the latter was obtained in the reaction of 3,3’-bithiophene with ninhydrin. The structures of these novel heterocycles were supported by spectroscopic studies and X-ray crystallography.