109588-48-9Relevant academic research and scientific papers
Synthetic use of 1,1,2,2-tetraphenyldisilane for the preparation of biaryls through the intramolecular free radical ipso-substitution of N-(2-bromoaryl)arenesulfonamides
Ryokawa, Atsushi,Togo, Hideo
, p. 5915 - 5921 (2007/10/03)
Treatment of various N-methyl-N-(2-bromoaryl)arenesulfonamides (1a-g, 1i, and 1m) with 1,1,2,2-tetraphenyldisilane and AIBN under heating conditions gave the corresponding biaryl products (2a-g, 2i, and 2m) in moderate yields through the intramolecular radical ipso-substitution. However, N-H free N-(2-bromoaryl)arenesulfonamides 1h and 2-bromoaryl arenesulfonate 1j did not give the corresponding biarys. 1,1,2,2-Tetraphenyldisilane is the most effective reagent for 1,5-ipso-substitution on the sulfonamides among typical radical reagents such as diphenylsilane, tributyltin hydride, tris(trimethylsilyl)silane, and 1,1,2,2-tetraphenyldisilane. Furthermore, 1,1,2,2-tetraphenyldisilane has the advantages of low toxicity, stability, and ease of preparation.
Bu3SnH mediated oxidative radical cyclisations: Synthesis of 6H-benzo[c]chromen-6-ones
Bowman, Russell,Mann, Emma,Parr, Jonathan
, p. 2991 - 2999 (2007/10/03)
Attempts to synthesise 6H-benzo[c]chromen-6-ones by Bu3SnH mediated cyclisation of o-(benzoyl)aryl radicals failed because of the preferred trans conformation of the ester. This problem was overcome by using cyclisation of o-(benzyloxy)aryl and o-[(aryloxy)methyl]aryl radicals to yield 6H-benzo[c]chromenes followed by oxidation to the 6H-benzo[c]chromen-6-ones. 3-Methoxy-6H-benzo[c]chromen-6-one 1, one of the main biologically active constituents of shilajit, a herbal medicine used in countries surrounding the Himalayan mountains, was synthesised using Bu3SnH mediated cyclisation of 1-benzyloxy-2,4-dibromo-5-methoxybenzene 31 to yield 3-methoxy-6H-benzo[c]chromene 25 followed by PCC oxidation of the 6-position. In order to avoid the problems of rearrangement, the aryl radical cyclisation must be designed such that whichever way the spirodienyl intermediate rearranges, the same product is obtained. For instance, the Bu3SnH mediated cyclisation of 1-iodo- and 1-bromo-2-(3-methoxy-phenyloxymethyl)benzenes 22 and 23 respectively gave both the isomers, 1-methoxy-6H-benzo[c]chromenes 24 and 3-methoxy-6H-benzo[c]chromenes 25 via rearrangement of the intermediate spirodienyl radical. The synthesised 6H-benzo[c]chromenes were oxidised in high yield to the corresponding 6H-benzo[c]chromen-6-ones. The mechanism of the 'oxidative' Bu3SnH mediated cyclisation is discussed.
