26127-98-0Relevant articles and documents
HIGHLY REACTIVE METALS FROM POTASSIUM-GRAPHITE. PREPARATION AND USE OF TITANIUM-GRAPHITE AND TIN-GRAPHITE
Boldrini, Gian Paolo,Savoia, Diego,Tagliavini, Emilio,Trombini, Claudio,Umani-Ronchi, Achille
, p. 307 - 312 (1985)
The potassium-graphite route to active forms of metals has been extended to the preparation of titanium-graphite (Ti-Gr) and tin-graphite (Sn-Gr).The Ti-Gr is used to achieve the reductive coupling of ketones to give alkenes, and Sn-Gr is used in the preparation of diallyltin dibromide complexes which react with aldehydes to give homoallylic alcohols.
Carboindation of Alkynes. Regio- and Stereoselective Allylation of Carbon-Carbon Triple Bonds of Alkynols by Allylic Indium Reagents
Araki, Shuki,Imai, Akira,Shimizu, Ken,Yamada, Masafumi,Mori, Akihiro,Butsugan, Yasuo
, p. 1841 - 1847 (2007/10/02)
Allylindium sesquihalides undergo smooth allylindation with terminal alkynes bearing a neighboring hydroxyl group at 100-140 deg C to give allylalkenols.The coupling occurred regioselectively at the γ-carbon of the allylindium reagents via syn-addition, whereas the regioselectivity concerning the alkynol depends upon the structures of both allylindium and alkynol.The allylation of nonfunctionalized alkynes is less efficient, requiring higher reaction temperature (150-180 deg C) and giving lower yields.Mechanistic considerations suggest a hydroxyl-assisted concerted process for the allylindation of alkynols, whereas a radical pathway is more likely for nonfunctionalized alkynes.Three monoterpene alcohols, i.e., yomogi alcohol, achillenol, and isomyrcenol, were conveniently prepared via allylindation of appropriate alkynols.
Carboindation of alkynols. A facile synthesis of yomogi alcohol
Araki, Shuki,Imai, Akira,Shimizu, Ken,Butsugan, Yasuo
, p. 2581 - 2582 (2007/10/02)
Carboindation of alkynols by ally lie indium sesquihalides proceeded in DMF at 100 - 140 °C via a synaddition; yomogi alcohol was prepared in onepot by this method.
Zwitterion-accelerated -Sigmatropic Rearrangements and -Sigmatropic Rearrangements of Sulphoxides and Amine Oxides
Hwu, Jih Ru,Anderson, Denise A.
, p. 3199 - 3206 (2007/10/02)
The effect of a zwitterionic moiety on -sigmatropic rearrangements has been studied.The allyl vinyl sulphoxide 5 underwent a -sigmatropic rearrangement at 23 deg C under neutral conditions to give the thione S-oxide 6 (96percent).This rearrangement (k1 = 1.56 +/- 0.04 x 10-1 h-1) was 45 times faster than conversion of the corresponding sulphide 3 into the thione 4 ( k1 = 3.5 +/- 0.1 x 10-3 h-1).At 23 deg C, the sulphoxide 7 also rearranged to give a mixture of (E)- and (Z)-thial S-oxide 8 (90percent).These experiments showed that the accelerating effect of the charges in the sulphoxide, a zwitterionic moiety, did not cancel out.Instead, the sulphoxide moiety significantly facilitated the -sigmatropic rearrangement.In the thermolysis of hexa-1,5-dienes with a zwitterionic moiety attached to the C-3 position ( e.g., 9 and 24), -sigmatropic rearrangements occurred.The conversion of the allyl sulphoxide 21 into the corresponding sulphenate ester 22 by a process was used as the key step in a total synthesis of yomogi alcohol 23, a biologically active monoterpenoid.
Highly Selective Carbon-Carbon Bond Forming Reactions Mediated by Chromium(II) Reagents
Hiyama, Tamejiro,Okude, Yoshitaka,Kimura, Keizo,Nozaki, Hitosi
, p. 561 - 568 (2007/10/02)
A low valent chromium reagent is generated from chromium(III) chloride and a half mol of lithium aluminum hydride in tetrahydrofuran.The reagent behaves similarly to anhydrous chromium(II) chloride, which is commercially available, and reduces allylic halides to produce unisolable allylchromium species which add efficiently to aldehydes or ketones with high degree of stereo- and chemoselectivity.Particularly, high threo selectivity is observed in the reaction of aldehydes and 1-bromo-2-butene and is ascribed to a chair-like six-membered transition state.Simple reduction od allylic and benzylic halides produces biallyls and bibenzyls, while gem-dibromocyclopropanes afford the corresponding allenes in excellent yields.