875877-89-7Relevant academic research and scientific papers
Catalytic deprotonative functionalization of propargyl silyl ethers with imines
Naka, Hiroshi,Koseki, Daiki,Kondo, Yoshinori
supporting information; experimental part, p. 1901 - 1906 (2009/08/07)
A metal-free, catalytic C-H functionalization of propargyl silyl ethers with imines using the phosphazene base (t-Bu-P4 base) provides structurally defined multisubstituted pyrroles in modest to excellent yields under mild conditions. A one-pot, three-component reaction using silylated acetylenes, aldehydes, and imines is also presented.
Siloxyallenes revisited. A useful functional intermediate for the synthesis of (Z)-β-branched Morita-Baylis-Hillman type adducts and (Z)-chalcones
Yoshizawa, Kazuhiro,Shioiri, Takayuki
, p. 6259 - 6286 (2008/02/04)
Siloxyallenes proved to be a useful functional intermediate in the preparation of (Z)-β-branched Morita-Baylis-Hillman type adducts by the reaction of aldehydes with silylacetylenes or siloxypropynes. Various (Z)-chalcones were stereoselectively synthesized from siloxypropynes via siloxyallenes.
Synthesis of β-branched Morita-Baylis-Hillman-type adducts from 1,3-diaryl-2-propynyl trimethylsilyl ethers and aldehydes catalyzed by potassium tert-butoxide
Yoshizawa, Kazuhiro,Shioiri, Takayuki
, p. 757 - 761 (2007/10/03)
1,3-Diaryl-2-propynyl trimethylsilyl ethers were easy to isomerize into the corresponding siloxyallenes using a catalytic amount of potassium tert-butoxide under very mild conditions. The siloxyallenes reacted in situ with various aldehydes to afford Z-selective β-branched Morita-Baylis-Hillman-type adducts in a one-pot reaction after acid treatment.
Nozaki-Hiyama-Kishi reactions catalytic in chromium
Fürstner, Alois,Shi, Nongyuan
, p. 12349 - 12357 (2007/10/03)
A procedure is described which allows for the first time to perform chromium-catalyzed additions of organic halides to aldehydes ("Nozaki-Hiyama-Kishi reactions"). The reactions are mediated by trimethylchlorosilane, and the active Cr2+ species is constantly recycled by means of nontoxic, commercial manganese powder as the stoichiometric reductant. This method nicely applies to different substituted aryl, heteroaryl, alkynyl, alkenyl, and allyl halides as well as to alkenyl inflates as the starting materials and rivals its stoichiometric precedent in terms of efficiency, practicability, and chemo- and diastereoselectivity. Specifically, it has been demonstrated that the addition of crotyl bromide to various aldehydes is highly stereoconvergent, i.e. the respective anti-configurated homoallyl alcohols are obtained with excellent diastereomeric excess independent of whether the starting halide is (E)- or (Z)-configurated. In accordance with the likely catalytic cycle, both CrCl2(cat.) or CrCl3(cat) turned out to efficiently mediate reactions of this type, with the latter being preferred for practical reasons. Finally, attempts were made to optimize the number of turnovers in chromium. In this context the use of either chromocene (Cp2Cr) or CpCrCl2·THF as "pre-catalysts" were found to significantly upgrade the efficiency of such C-C bond formations, with ≤ 1 mol % of chromium being required in these cases for quantitative conversions.
