Bromination of bromosubstituted indanones

Key Words: photobromination, bromoindanones, bromoindenones A rapid growth on the synthetic work of indenones has taken place in the last three decades. Indenones are useful intermediates in the synthesis of a variety of molecules. Bromoindenones are also valuable precursor for preparation of ninhydrin analogs, used determination of finger prints. Despite the considerable biological and synthetic interest in indenones and indenols, very few general and flexible synthetic routes to these compounds have been reported. A logical synthetic precursor is the corresponding indanone, but poor yields, irreproducibility, or decomposition of the starting material have made this route unattractive. In this study, the low and high temperature bromination reactions of 4- bromoindanone (2.2), 5-bromoindanone (2.3) ve 6-bromoindanone (2.4) molecules were investigated with molecular bromine and N-bromosuccinimide. Spesific and selective routes were developed for derivatives of bromosubsituted indanones. First, we studied the electrophilic bromination of 4-bromoindanone (2.2). The 2,2,4- tribromoindanone (4.1) was obtained as the sole product in high yield. Photolytic bromination of 4-B? (2.2) both bromine and NBS gave 2,4-dibromoindenone (4.2) as the sole product. Second, we investigated the low temperature bromination of 5- bromoindanone (2.3) in methylene chloride and we isolated 2,2,5-tribromoindanone (4.6) in a yield of 90% yield as the sole product after flash column chromatography. The radicalic bromination of bilesik 2.3 using excess amount of NBS and bromine followed by elimination with triethylamine gave 2,3,5-tribromindanon (4.7) in 58% yield. We also have studied both ionic and radicalic bromination of 6- bromoindanone (2.4) using NBS and bromine, and we obtained 2,2,6 tribromondanone (4.14) and 2,3,6-tribromoindenone (4.15) as sole product respectively.