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Rhodium‐Catalyzed Silylative and Germylative Cyclization with Dehydrogenation Leading to 9‐Sila‐ and 9‐Germafluorenes: A Combined Experimental and Computational Mechanistic Study
Author(s) -
Murai Masahito,
Okada Ryo,
Asako Sobi,
Takai Kazuhiko
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201701579
Subject(s) - dehydrogenation , silylation , chemistry , metalation , catalysis , stoichiometry , reaction rate constant , density functional theory , medicinal chemistry , photochemistry , combinatorial chemistry , organic chemistry , computational chemistry , kinetics , physics , quantum mechanics
Abstract 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 PPh 3 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.