TY - JOUR
T1 - Rhodium-Catalyzed Silylative and Germylative Cyclization with Dehydrogenation Leading to 9-Sila- and 9-Germafluorenes
T2 - A Combined Experimental and Computational Mechanistic Study
AU - Murai, Masahito
AU - Okada, Ryo
AU - Asako, Sobi
AU - Takai, Kazuhiko
N1 - Funding Information:
This work was financially supported by a Grant-in-Aid for Scientific Research (A) (No. 26248030 to K.T.) and Scientific Research (C) (No. 16K05778 to M.M.) from MEXT, Japan, and the Mitsubishi Foundation (Research Grants in the Natural Sciences). The generous amount of computational time from the Research Center for Computational Science, Okazaki National Research Institute, is gratefully acknowledged.
Publisher Copyright:
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2017/8/10
Y1 - 2017/8/10
N2 - Stoichiometric amounts of oxidants are widely used as promoters (hydrogen acceptors) in dehydrogenative silylation of C−H bonds. However, the present study demonstrates that silylative and germylative cyclization with dehydrogenation can proceed efficiently, even without hydrogen acceptors. The combination of [RhCl(cod)]2 and PPh3 was effective for both transformations, and allowed a reduction in reaction temperature compared with our previous report. Monitoring of the reactions revealed that both transformations had an induction period for the early stage, and that the rate constant of dehydrogenative germylation was greater than that of dehydrogenative silylation. Competitive reactions in the presence of 3,3-dimethyl-1-butene indicated that the ratio of dehydrogenative metalation and hydrometalation was affected by reaction temperature when a hydrosilane or hydrogermane precursor was used. Further mechanistic insights of oxidant-free dehydrogenative silylation, including the origin of these unique reactivities, were obtained by density functional theory studies.
AB - Stoichiometric amounts of oxidants are widely used as promoters (hydrogen acceptors) in dehydrogenative silylation of C−H bonds. However, the present study demonstrates that silylative and germylative cyclization with dehydrogenation can proceed efficiently, even without hydrogen acceptors. The combination of [RhCl(cod)]2 and PPh3 was effective for both transformations, and allowed a reduction in reaction temperature compared with our previous report. Monitoring of the reactions revealed that both transformations had an induction period for the early stage, and that the rate constant of dehydrogenative germylation was greater than that of dehydrogenative silylation. Competitive reactions in the presence of 3,3-dimethyl-1-butene indicated that the ratio of dehydrogenative metalation and hydrometalation was affected by reaction temperature when a hydrosilane or hydrogermane precursor was used. Further mechanistic insights of oxidant-free dehydrogenative silylation, including the origin of these unique reactivities, were obtained by density functional theory studies.
KW - C−H activation
KW - dehydrogenation
KW - germylation
KW - rhodium
KW - silylation
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U2 - 10.1002/chem.201701579
DO - 10.1002/chem.201701579
M3 - Article
C2 - 28557136
AN - SCOPUS:85027363827
VL - 23
SP - 10861
EP - 10870
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
IS - 45
ER -