Efficient Access to Substituted Silafluorenes by Nickel‐Catalyzed Reactions of Biphenylenes with Et2SiH2. Issue 11 (9th September 2014)

• Record Type: Journal Article
• Authors: Breunig, Jens Michael; Gupta, Puneet; Das, Animesh; Tussupbayev, Samat; Diefenbach, Martin; Bolte, Michael; Wagner, Matthias; Holthausen, Max C.; Lerner, Hans‐Wolfram
• Is Part Of: Chemistry, an Asian journal. Volume 9:Issue 11(2014:Nov.)
• Page Start: 3163
• Page End: 3173
• Publication Date: 2014-09-09
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.201402599
• Languages: English
• ISSNs: 1861-4728

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The reaction of biphenylene (<bold>1</bold>) with Et<sub>2</sub>SiH<sub>2</sub> in the presence of [Ni(PPhMe<sub>2</sub>)<sub>4</sub>] results in the formation of a mixture of 2‐diethylhydrosilylbiphenyl [<bold>2</bold>(Et<sub>2</sub>HSi)] and 9, 9, ‐diethyl‐9‐silafluorene (<bold>3</bold>). Silafluorene <bold>3</bold> was isolated in 37.5 % and <bold>2</bold>(Et<sub>2</sub>HSi) in 36.9 % yield. The underlying reaction mechanism was elucidated by DFT calculations. 4‐Methyl‐9, 9‐diethyl‐9‐silafluorene (<bold>7</bold>) was obtained selectively from the [Ni(PPhMe<sub>2</sub>)<sub>4</sub>]‐catalyzed reaction of Et<sub>2</sub>SiH<sub>2</sub> and 1‐methylbiphenylene. By contrast, no selectivity could be found in the Ni‐catalyzed reaction between Et<sub>2</sub>SiH<sub>2</sub> and the biphenylene derivative that bears <italic>t</italic>Bu substituents in the 2‐ and 7‐positions. Therefore, two pairs of isomers of <italic>t</italic>Bu‐substituted silafluorenes and of the related diethylhydrosilylbiphenyls were formed in this reaction. However, a subsequent dehydrogenation of the diethylhydrosilylbiphenyls with Wilkinson's catalyst yielded a mixture of 2, 7‐di‐<italic>tert</italic>‐butyl‐9, 9‐diethyl‐9‐silafluorene (<bold>8</bold>) and 3, 6‐di‐<italic>tert</italic>‐butyl‐9, 9‐diethyl‐9‐silafluorene (<bold>9</bold>). Silafluorenes <bold>8</bold> and <bold>9</bold> were separated by column chromatography.</p> </abstract>