Highly Stereoselective Construction of Acyclic Systems by the Reaction of Allyl and Allenyltitanocenes with Ketones

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  • Takeda Takeshi
    Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology
  • Yatsumonji Yasutaka
    Organic Synthesis Research Laboratory, Sumitomo Chemical Co., Ltd.
  • Tsubouchi Akira
    Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology

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  • アリル·プロパルギルチタノセンとケトンの反応による鎖状化合物の高立体選択的構築
  • アリル ・ プロパルギルチタノセン ト ケトン ノ ハンノウ ニ ヨル サジョウ カゴウブツ ノ コウリッタイ センタクテキ コウチク

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Abstract

Highly diastereoselective preparation of tert-homoallylic alcohols using organotitanium reagents is described. The reaction of allyltitanocenes, generated by the reductive titanation of allylic sulfides with titanocene(II)-1-butene complex, with phenyl and sterically hindered alkyl methyl ketones produced anti-tertiary homoallylic alcohols with complete diastereoselectivity. Even when sterically less congested alkyl methyl ketones such as methyl ethyl ketone and cyclic enones were employed, the homoallylic alcohols were obtained with unprecedented high diastereoselectivity. Using α-silyl allyl sulfides, β,δ-disubstituted tertiary homoallylic alcohols were obtained with high regio- and stereoselectivity. A range of syn-tertiary homoallylic alcohols were also obtained by the reaction of α-silylallenyltitanocenes generated by the reductive titanation of γ-silylpropargylic carbonates with titanocene(II)-triethyl phosphite complex, with ketones and following desilylation and partial hydrogenation. The construction of three consecutive stereogenic centers has been achieved by two approaches, the addition of allyltitanium reagents to α-chiral ketones and the reaction of ketones with chiral allyltitanocenes generated by the desulfurizative titanation of allylic sulfides obtained by the alkylation of allyl sulfide with secondary halides. Acyclic systems bearing adjacent two quaternary centers were also constructed by the use of allyltitanocenes, generated by the desulfurizative titanation of γ,γ-disubstituted allyl sulfides.

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