4378-00-1Relevant articles and documents
Generation of α,β-unsaturated platinum carbenes from homopropargylic alcohols: Rearrangements to polysubstituted furans
Allegretti, Paul A.,Ferreira, Eric M.
, p. 5924 - 5927 (2011/12/16)
A number of diversely substituted furans are synthesized via a cycloisomerization process that goes through a unique metal carbene species. Both ligand structure and the nature of the leaving group are evaluated. The characteristics of the carbene intermediate can be modulated, resulting in highly selective hydrogen or silicon group migrations.
1,2-Silyl-migrative cyclization of vinylsilanes bearing a hydroxy group: Stereoselective synthesis of multisubstituted tetrahydropyrans and tetrahydrofurans
Miura, Katsukiyo,Hondo, Takeshi,Okajima, Shigeo,Nakagawa, Takahiro,Takahashi, Tatsuyuki,Hosomi, Akira
, p. 6082 - 6090 (2007/10/03)
Acid-catalyzed intramolecular addition of a hydroxy group to α-alkylated vinylsilanes has been studied. Treatment of (Z)-5-alkyl-5-silyl-4-penten-1-ols 1 (R = alkyl) with 5 mol % TiCl4 in CHCl3 gave trans-2-alkyl-3-silyltetrahydropyrans 2 exclusively (trans/cis = > 99/1 to 97/3). The cyclization efficiency and rate strongly depended on the geometry of the C-C double bond and the silyl group. The use of (E)-vinylsilanes resulted in lower yields with poor cis-selectivity. In the cyclization of (Z)-1 (R = Bu), the silyl group used, the reaction time, and the yield of 2 were as follows: SiMe2Ph, 9.5 h, 75%; SiMe3, 7.5 h, 66%; SiMePh2, 24 h, 58%; SiMe2-t-Bu, 0.75 h, 85%; SiMe2Bn, 1.5 h, 78%. This 1,2-silyl-migrative cyclization could be applied to stereoselective synthesis of trisubstituted tetrahydropyrans. The acid-catalyzed reaction of 1-, 2-, or 3-substituted (Z)-5-silyl-4-nonen-1-ols 8 gave r-2,t-3,c-6-, r-2,t-3,t-5-, or r-2,t-3,c-4-trisubstituted tetrahydropyrans with high diastereo-selectivity, respectively. (Z)-4-Alkyl-4-silyl-3-buten-1-ols 5 as well as 1 underwent the 1,2-silylmigrative cyclization to give 2-alkyl-3-silyltetrahydrofurans 6 with high trans-selectivity. This silicon-directed cyclization was also available for the stereoselective synthesis of tri- and tetrasubstituted tetrahydrofurans.