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Efficient Access to Substituted Silafluorenes by Nickel‐Catalyzed Reactions of Biphenylenes with Et 2 SiH 2
Author(s) -
Breunig Jens Michael,
Gupta Puneet,
Das Animesh,
Tussupbayev Samat,
Diefenbach Martin,
Bolte Michael,
Wagner Matthias,
Holthausen Max C.,
Lerner HansWolfram
Publication year - 2014
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201402599
Subject(s) - chemistry , catalysis , dehydrogenation , yield (engineering) , nickel , biphenylene , selectivity , medicinal chemistry , derivative (finance) , organic chemistry , materials science , polymer , phenylene , economics , financial economics , metallurgy
The reaction of biphenylene ( 1 ) with Et 2 SiH 2 in the presence of [Ni(PPhMe 2 ) 4 ] results in the formation of a mixture of 2‐diethylhydrosilylbiphenyl [ 2 (Et 2 HSi)] and 9,9,‐diethyl‐9‐silafluorene ( 3 ). Silafluorene 3 was isolated in 37.5 % and 2 (Et 2 HSi) in 36.9 % yield. The underlying reaction mechanism was elucidated by DFT calculations. 4‐Methyl‐9,9‐diethyl‐9‐silafluorene ( 7 ) was obtained selectively from the [Ni(PPhMe 2 ) 4 ]‐catalyzed reaction of Et 2 SiH 2 and 1‐methylbiphenylene. By contrast, no selectivity could be found in the Ni‐catalyzed reaction between Et 2 SiH 2 and the biphenylene derivative that bears t Bu substituents in the 2‐ and 7‐positions. Therefore, two pairs of isomers of t 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‐ tert ‐butyl‐9,9‐diethyl‐9‐silafluorene ( 8 ) and 3,6‐di‐ tert ‐butyl‐9,9‐diethyl‐9‐silafluorene ( 9 ). Silafluorenes 8 and 9 were separated by column chromatography.