- Iterative stereospecific reagent-controlled homologation using a functionalized α-chloroalkyllithium: Synthesis of cyclic targets related to epibatidine
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Enantioenriched 1-chloro-2-(1,3-dioxolan-2-yl)ethyllithium was generated by PhLi initiated sulfoxide-ligand exchange and deployed in situ for sequential double stereospecific reagent-controlled homologation (StReCH) of B-(2-chloro-pyrid-5-yl) pinacol boronate. This process afforded highly functionalized contiguous stereodiad motifs (typically, % ee ≥ 98%, dr ≥ 85:15) amenable to subsequent annulative transformations as demonstrated by the concise synthesis (5-7 steps) of cyclic adducts related to the analgesic alkaloid epibatidine.
- Emerson, Christopher R.,Zakharov, Lev N.,Blakemore, Paul R.
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supporting information; experimental part
p. 1318 - 1321
(2011/04/26)
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- New cyclic phosphonium salts derived from the reaction of phosphine-aldehydes with acid
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Various cyclic phosphonium structures are formed in high yield by the deprotection of unstable phosphine-aldehydes in acidic solution. When there is a methylene spacer between the phosphine and the aldehyde, a phosphonium ion [PHR2CH2CH(OEt)2]Br2, R=iPrOH, Et is obtained. Reaction of these phosphonium salts with water produces the dimers [-PR2CH2CH(OH)-]2[Br]2?R = iPr, Et. When there is an ethylene spacer as in PPh2CH2CH2CH(OCH2CH2O), a remarkable tetramer with a 16-membered ring [-PPh2CH2CH2CH (OH)-]4[Cl]4 forms as one diastereomer in hydrochloric acid solution. Reaction of HCl with the protected phosphine-aldehyde with a propylene spacer (PPh2CH2CH2CH2CH(OCH2CH2O)) results in the formation of the monomeric phosphonium salt [-PPh2 CH2CH2CH2CH(OH)-]Cl with a 5-membered ring. Solid state structures of different ring types were determined using X-ray diffraction experiment.
- Mikhailine, Alexandre A.,Lagaditis, Paraskevi O.,Sues, Peter E.,Lough, Alan J.,Morris, Robert H.
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scheme or table
p. 1824 - 1830
(2010/08/06)
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- Preparation of [1,2,3,4,5-13C 5]-5-Amino-4-oxopentanoic Acid (ALA) - Design of a Synthetic Scheme to Prepare Any 13C- and 15N-Isotopomer with High Isotopic Enrichment
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5-Amino-4-oxopentanoic acid (5-aminolevulinic acid) is a precursor in the biosynthesis of the biologically active porphyrins such as chlorophyll, bacteriochlorophyll, heme, etc. These systems are central in photosynthesis, oxygen transport, electron transport, etc. In this paper we describe a simple scheme to prepare any isotopomer of 5-aminolevulinic acid in a few steps in high yield. Using a similar scheme, levulinic acid can now also be prepared in any isotopomeric form. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Shrestha-Dawadi, Prativa Bade,Lugtenburg, Johan
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p. 4654 - 4663
(2007/10/03)
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- A Short Synthesis of 2H-1-Benzopyrans
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A two-step process for synthesizing 2H-1-benzopyrans from phenols and β-halopropionaldehyde acetals is detailed.
- Schuda, Paul Francis,Phillips, Jennifer L.
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p. 669 - 672
(2007/10/02)
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- LES ORGANOSILICIQUES COMME AGENTS DE SYNTHESE D'ACETALS β-HALOGENES
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The reactions of unsaturated aldehydes and ketones with diols in presence of halogenosilane lead to the synthesis of halogenoacetals in yields of 60-97percent.
- GIL, Gerard
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p. 3805 - 3808
(2007/10/02)
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