Papers - YASUKAWA Naoki
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Disiloxane Synthesis Based on Silicon–Hydrogen Bond Activation using Gold and Platinum on Carbon in Water or Heavy Water International journal
Yoshinari Sawama, Masahiro Masuda, Naoki Yasukawa, Ryosuke Nakatani, Shumma Nishimura, Kyoshiro Shibata, Tsuyoshi Yamada, Yasunari Monguchi, Hiroyasu Suzuka, Yukio Takagi, Hironao Sajiki
The Journal of Organic Chemistry 81 ( 10 ) 4190 - 4195 2016.05
Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society ({ACS})
Disiloxanes possessing a silicon-oxygen linkage are important as frameworks for functional materials and coupling partners for Hiyama-type cross coupling. We found that disiloxanes were effectively constructed of hydrosilanes catalyzed by gold on carbon in water as the solvent and oxidant in association with the emission of hydrogen gas at room temperature. The present oxidation could proceed via various reaction pathways, such as the hydration of hydrosilane into silanol, dehydrogenative coupling of hydrosilane into disilane, and the subsequent corresponding reactions to disiloxane. Additionally, the platinum on carbon catalyzed hydrogen-deuterium exchange reaction of arylhydrosilanes as substrates in heavy water proceeded on the aromatic nuclei at 80 °C with high deuterium efficiency and high regioselectivity at the only meta and para positions of the aromatic-silicon bond to give the deuterium-labeled disiloxanes.
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Additional Nucleophile-Free FeCl<sub>3</sub>-Catalyzed Green Deprotection of 2,4-Dimethoxyphenylmethyl-Protected Alcohols and Carboxylic Acids
Yoshinari Sawama, Masahiro Masuda, Akie Honda, Hiroki Yokoyama, Kwihwan Park, Naoki Yasukawa, Yasunari Monguchi, Hironao Sajiki
Chemical and Pharmaceutical Bulletin 64 ( 7 ) 778 - 784 2016
Language：English Publishing type：Research paper (scientific journal) Publisher：Pharmaceutical Society of Japan
The deprotection of the methoxyphenylmethyl (MPM) ether and ester derivatives can be generally achieved by the combinatorial use of a catalytic Lewis acid and stoichiometric nucleophile. The deprotections of 2,4-dimethoxyphenylmethyl (DMPM)-protected alcohols and carboxylic acids were found to be effectively catalyzed by iron(III) chloride without any additional nucleophile to form the deprotected mother alcohols and carboxylic acids in excellent yields. Since the present deprotection proceeds via the self-assembling mechanism of the 2,4-DMPM protective group itself to give the hardly-soluble resorcinarene derivative as a precipitate, the rigorous purification process by silica-gel column chromatography was unnecessary and the sufficiently-pure alcohols and carboxylic acids were easily obtained in satisfactory yields after simple filtration.
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Biarylmethane and Fused Heterocyclic Arene Synthesis via in Situ Generated o- and/or p-Naphthoquinone Methides International journal
Yoshinari Sawama, Takahiro Kawajiri, Shota Asai, Naoki Yasukawa, Yuko Shishido, Yasunari Monguchi, Hironao Sajiki
The Journal of Organic Chemistry 80 ( 11 ) 5556 - 5565 2015.05
Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society ({ACS})
o- and/or p-naphthoquinone methides (NQMs) can be selectively prepared by the ring opening of 1-(siloxymethyl)-1,4-epoxy-1,4-dihydronaphthalene derivatives based on a substituent effect at the 4 position of the substrates. The 4-alkyl- or silyl-substituted 1-(siloxymethyl)-1,4-epoxy-1,4-dihydronaphthalene was transformed to o-NQM (1-naphthoquinone-2-methide), which underwent Friedel-Crafts 1,4-addition of the α,β-unsaturated carbonyl moiety to provide the 2-benzyl-1-naphthol as the biarylmethane and [4 + 2]-cycloaddition with a dienophile to give the fused heterocyclic arene. Meanwhile, the 4-unsubstituted 1-(siloxymethyl)-1,4-epoxy-1,4-dihydronaphthalene could be converted to the corresponding 4-benzyl-1-naphthol by the Friedel-Crafts 1,6-addition of p-NQM (1-naphthoquinone-4-methide) generated by the site-selective ring opening of the 1,4-epoxy moiety. Furthermore, the 4-(siloxymethyl)-(1,4-bis(siloxymethyl))-1,4-epoxy-1,4-dihydronaphthalene was transformed into a 2,4-bisbenzyl-1-naphthol or pentacyclic derivative via both the o- and p-NQM intermediates.
