514-50-1Relevant articles and documents
Electrochemical bromination of cholest-5-enes
Milisavljevic, Smiljka S.,Wurst, Klaus,Laus, Gerhard,Vukicevic, Mirjana D.,Vukicevic, Rastko D.
, p. 867 - 872 (2005)
Four 5,6-unsaturated steroids - 3β-chlorocholest-5-ene (1a), cholesterol (1b) and its acetate (1c) and benzoate (1d) - were subjected to constant current electrolysis (50 mA, 2 F mol-1) in an electrolytic cell divided by a ceramic membrane, using a platinum foil as the anode and a graphite stick as the cathode. When electrolysis was carried out in a solution of tetraethylammonium bromide in aprotic solvents (dichloromethane, acetonitrile or acetic anhydride), the addition of electrochemically-generated elemental bromine onto the double bond of the cholesterol derivatives gave their corresponding 5α,6β-dibromosteroids - 3β-chloro-5α, 6β-dibromocholestane (2a), 5α,6β-dibromocholestan-3β-ol (2b), 5α,6β-dibromocholestan-3β-yl acetate (2c) and 5α,6β-dibromocholestan-3β-yl benzoate (2d) - as the sole products, and in good yields (58-91%). However, the electrolysis of steroids 1a-c in a solution of tetraethylammonium bromide with methanol as the solvent proceeded to give, in addition to dibromides 2a-c, the corresponding diastereomeric pairs of 5-bromo-6-methoxysteroids: 5α-bromo-3β- chloro-6β-methoxycholestane (3a) and 5β-bromo-3β-chloro-6α- methoxycholestane (4a), 5α-bromo-6β-methoxycholestan-3β-ol (3b) and 5β-bromo-6α-methoxycholestan-3β-ol (4b) and 5α-bromo-6β-methoxycholestan-3β-yl acetate (3c) and 5α-bromo-6β-methoxycholestan-3β-yl acetate (4c). The benzoate 1d was not soluble enough in methanol, even with heating. The products were characterized by physical and spectral data (IR, 1H NMR and 13C NMR). Single crystal X-ray structure determinations of compounds 2a and 3a are also reported.
Preparation of oxysterols by c–h oxidation of dibromocholestane with ru(Bpga) catalyst
Doiuchi, Daiki,Fujii, Yui,Hirai, Go,Igawa, Kazunobu,Makino, Kana,Takeda, Daiki,Tomooka, Katsuhiko,Uchida, Tatsuya,Yoritate, Makoto
, (2022/01/04)
Seven mono-and dihydroxycholesterols were prepared by direct C–H oxidation of the cholestane skeleton with a recently developed Ru(Bpga) catalyst (Ru(Bpga) = [RuCl (bpga) (PPh3 )] Cl; bpga = 2-(bis(pyridin-2-ylmethyl)amino)-N-(2,6-dimethylphenyl)acetamide)). Due to the high selectivity of the Ru(Bpga) complex for tertiary C–H, the reaction afforded a mixture of 25-, 20-, 17-, and 14-oxygenated cholesterols that could be easily separated by high-performance liquid chromatography. These results suggest that late-stage C–H oxidation could be a viable strategy for preparing candidate metabolites of biologically important molecules.
Halocarbocyclization versus dihalogenation: Substituent directed iodine(iii) catalyzed halogenations
Stodulski, Maciej,Goetzinger, Alissa,Kohlhepp, Stefanie V.,Gulder, Tanja
supporting information, p. 3435 - 3438 (2014/03/21)
The nucleophilicity of the substituents in iodobenzene pre-catalysts have a huge impact on product selectivity in iodine(iii) triggered halogenations, steering the reactivity from solely carbocyclizations towards dihalogenations. Utilizing this catalyst-dependent reactivity a diastereo- and chemoselective dihalogenation method was established allowing the conversion of structurally and electronically diverse unsaturated compounds in excellent yields.
Rapid debromination of vic-dibromoalkanes with zinc powder in acetic acid under microwave irradiation
Kuang, Chunxiang,Yang, Qing,Senboku, Hisanori,Tokuda, Masao
, p. 282 - 284 (2007/10/03)
Microwave irradiation of vic-dibromoalkanes in acetic acid containing zinc powder for 1-2 min gave the corresponding alkenes in high yields.
Oxidation of Natural Targets by Dioxiranes. 2. Direct Hydroxylation at the Side-Chain C-25 of Cholestane Derivatives and of Vitamin D3 Windaus-Grundmann Ketone
Bovicelli, Paolo,Lupattelli, Paolo,Mincione, Enrico,Prencipe, Teresa,Curci, Ruggero
, p. 5052 - 5054 (2007/10/02)
The direct, high-yield oxyfunctionalization of the side-chain C-25 of 5α-cholestan-3-one, 3β-acetoxy-5α-cholestane, and 5α,6β-Br2-3β-acetoxycholestane as well as of the vitamin D3-derived Windaus-Grundmann ketone has been achieved under mild conditions employing either dimethyldioxirane or its trifluoromethyl analogue.
An Improved Synthesis of 1α-hydroxy Vitamin D3
Nerinckx, W.,Clercq, P. J. De,Couwenhoven, C.,Overbeek, W. R. M.,Halkes, S. J.
, p. 9419 - 9430 (2007/10/02)
The efficient and stereoselective introduction of the 1α-OH function in vitamin D3 is described starting from the known previtamin D3 adduct 6.The sequence involves the stereoselective allylic bromination to 9, followed by substituti
