TY - JOUR
T1 - Syntheses of Substituted 1,4-Disila-2,5-cyclohexadienes from Cyclic Hexasilane Si6Me12 and Alkynes via Successive Si-Si Bond Activation by Pd/Isocyanide Catalysts
AU - Tahara, Atsushi
AU - Nagino, Shunsuke
AU - Sunada, Yusuke
AU - Haige, Ryohei
AU - Nagashima, Hideo
N1 - Funding Information:
This work was supported by Integrated Research Consortium on Chemical Sciences (IRCCS), the Cooperative Research Program of “Network Joint Research Center for Materials and Devices” and Grant in Aid for Young Scientist (B) (No. 17K17944) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. The helpful suggestion by Prof. Hiromi Tobita, Tohoku University, is acknowledged. We also thank Prof. Soichiro Kyushin, Gunma University, for the support of the preparation of Si6Me12.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/8/13
Y1 - 2018/8/13
N2 - Palladium-catalyzed reactions of dodecamethylcyclohexasilane [(SiMe2)6] (1) with alkynes led to efficient preparation of 1,1,4,4-tetramethyl-1,4-disilacyclohexadienes (3). The reactions were best catalyzed by Pd(0) species generated from Pd2(dba)3·CHCl3 and 1-isocyanoadamantane (AdNC). Terminal and internal alkynes bearing aryl and alkyl substituents could be used as substrates, and the reaction allowed gram-scale preparation of 3. A dimethylsilylene (Me2Si:) species, generated by activation of Si-Si bonds in 1 by Pd(0) species, was involved in the reaction mechanism. The DFT calculations suggest that oxidative addition of Si-Si bonds in 1 to Pd(CNAd)2 species is followed by extrusion of a Me2Siâ•Pd(CNAd) intermediate. Reaction of the resulting palladium-coordinated silylene with an alkyne forms a silacyclopropene, which dimerizes to give 3. The extrusion is accompanied by ring contraction of 1 to generate (SiMe2)5, which also contributes to formation of 3 and (SiMe2)4 by the Pd(0)-catalyzed reaction with an alkyne. Extrusion of Me2Siâ•Pd(CNAd) and ring contraction generated more than five Me2Si: species from (SiMe2)6 (1).
AB - Palladium-catalyzed reactions of dodecamethylcyclohexasilane [(SiMe2)6] (1) with alkynes led to efficient preparation of 1,1,4,4-tetramethyl-1,4-disilacyclohexadienes (3). The reactions were best catalyzed by Pd(0) species generated from Pd2(dba)3·CHCl3 and 1-isocyanoadamantane (AdNC). Terminal and internal alkynes bearing aryl and alkyl substituents could be used as substrates, and the reaction allowed gram-scale preparation of 3. A dimethylsilylene (Me2Si:) species, generated by activation of Si-Si bonds in 1 by Pd(0) species, was involved in the reaction mechanism. The DFT calculations suggest that oxidative addition of Si-Si bonds in 1 to Pd(CNAd)2 species is followed by extrusion of a Me2Siâ•Pd(CNAd) intermediate. Reaction of the resulting palladium-coordinated silylene with an alkyne forms a silacyclopropene, which dimerizes to give 3. The extrusion is accompanied by ring contraction of 1 to generate (SiMe2)5, which also contributes to formation of 3 and (SiMe2)4 by the Pd(0)-catalyzed reaction with an alkyne. Extrusion of Me2Siâ•Pd(CNAd) and ring contraction generated more than five Me2Si: species from (SiMe2)6 (1).
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U2 - 10.1021/acs.organomet.8b00302
DO - 10.1021/acs.organomet.8b00302
M3 - Article
AN - SCOPUS:85051434777
SN - 0276-7333
VL - 37
SP - 2531
EP - 2543
JO - Organometallics
JF - Organometallics
IS - 15
ER -