- Solvent-free organic reactions on silica gel supports. Facile transformation of epoxides to β-halohydrins with lithium halides
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The reaction of epoxides with lithium halides was efficiently promoted on the surface of silica gel in the absence of any solvent to give the corresponding β-halohydrins. The reactivity of lithium halides was shown to follow the order LiI > LiBr >> LiCl, and the reactivity of LiCl was dramatically increased by adding an equivalent amount of water to this system. On the other hand a similar reaction with α,β-epoxyketones produces the α-haloenone derivatives, presumably via halohydrin intermediates. The epoxide-opening reaction of (R)-(+)-styrene oxide was also investigated to clarify the stereochemical features of this reaction.
- Kotsuki, Hiyoshizo,Shimanouchi, Tomoyasu,Ohshima, Reiji,Fujiwara, Shunsuke
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Read Online
- Stereospecific Overman Rearrangement of Substituted Cyclic Vinyl Bromides: Access to Fully Substituted α-Amino Ketones
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A versatile thermal Overman rearrangement of enantioenriched, cyclic allylic alcohols providing tertiary allylic amines has been developed. The vinyl bromide used to control enantioselectivity in a preceding CBS reduction is utilized as a synthetic handle
- Velasco-Rubio, álvaro,Alexy, Eric J.,Yoritate, Makoto,Wright, Austin C.,Stoltz, Brian M.
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supporting information
p. 8962 - 8965
(2019/11/14)
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- Synthetic Study toward the Total Synthesis of Taxezopidines A and B
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A concise synthetic approach to construct the [6,8,6]-tricyclic core of taxezopidines A and B, which contains a synthetically challenging bridged bicyclo[5.3.1]undecane ring system bearing most of the desired functionalized groups and stereocenters, has b
- Fan, Jian-Hong,Hu, Ya-Jian,Li, Chuang-Chuang,Li, Shaoping,Zhao, Jing
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p. 5905 - 5909
(2018/09/21)
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- Efficient Synthesis of Anastrephin via the Allylic Substitution for Quaternary Carbon Construction
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Lactone-moiety-attached 2-cyclohexylideneethyl picolinate was prepared through the OH-directed epoxidation (98% ds) of (R)-3-methylcyclohex-2-en-1-ol (99% ee), Horner-Wadsworth-Emmons olefination, conversion to the allylic moiety, and epoxide ring opening
- Wada, Kyohei,Sakai, Masahiro,Kawashima, Hidehisa,Ogawa, Narihito,Kobayashi, Yuichi
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p. 1428 - 1432
(2016/05/24)
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- Synthesis of 4,6-dimethyldibenzothiophene and 1,2,3,4-tetrahydro-4,6- dimethyldibenzothiophene via Tilak annulation
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1,2,3,4-Tetrahydro-4,6-dimethyldibenzothiophene was prepared by coupling 2-bromo-3-methylcyclohexanone with 2-methylbenzenethiol and annulating the product with the aid of polyphosphoric acid. A mixture of 1,2,3,4-tetrahydro-4, 6-dimethyldibenzothiophene and 4,6-dimethyldibenzothiophene was prepared by coupling 2-bromo-3-methylcyclohex-2-en-1-one with 2-methylbenzenethiol and annulating the product with the aid of polyphosphoric acid. 2-Bromo-3- methylcyclohexanone was synthesized by conjugate addition of Me3Al to 2-bromocyclohex-2-en-1-one with CuBr as catalyst and 2-bromo-3-methylcyclohex- 2-en-1-one by bromination-elimination of 3-methylcyclohex-2-en-1-one. 1,2,3,4,4a,9b-Hexahydro-4,6-dimethyldibenzothiophene was prepared by reduction of 1,2,3,4-tetrahydro-4,6-dimethyldibenzothiophene with Zn and CF 3COOH. Copyright
- Xu, Xiaoying,Li, Xiang,Wang, Anjie,Sun, Yinyong,Schweizer, W. Bernd,Prins, Roel
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experimental part
p. 1754 - 1763
(2011/12/03)
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- Cyclic α-acylvinyl anionic synthons: A novel synthesis of 2-trimethylsilyl-3-methyl-cyclohexenone by the Wurtz-Fittig coupling reaction
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2-Trimethylsilyl-3-methyl-cyclohexen-1-one: a cyclic α-acyl anionic synthon was prepared in good yield by the Wurtz-Fittig coupling reaction of 6-bromo-7-methyl-1,4-dioxaspiro[4,5]-6-decene with metallic sodium and chlorotrimethylsilane in anhydrous ether solvent. Copyright Taylor & Francis Group, LLC.
- Jyothi, Divya,HariPrasad
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body text
p. 875 - 879
(2009/09/05)
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- A remarkably simple one-step procedure for the preparation of α-bromo-α,β-unsaturated carbonyl compounds
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An easy and convenient one-step procedure for the conversion of α,β-unsaturated carbonyl compounds into their corresponding bromo-enones using NBS-Et3N·3HBr in the presence of potassium carbonate in dichloromethane at 0°C to room temperature under very mild conditions in high yields and significantly shorter times, is reported. Georg Thieme Verlag Stuttgart.
- Jyothi, Divya,Hariprasad
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experimental part
p. 2309 - 2311
(2009/12/08)
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- Stereoselective solvent induced 1,3-proton transfer of an allylic alkoxide to a homoallylic alkoxide catalysed by a chiral lithium amide
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Stereoselective rearrangements of e.g. meso-epoxides by chiral lithium amides yield chiral allylic alcohols in high enantiomeric excess. Such products are useful synthetic intermediates. Lithium (S)-2-(pyrrolidin-1-ylmethyl)-pyrrolidide Li-2 has been foun
- Hansson, Maria,Arvidsson, Per I.,Nilsson Lill, Sten O.,Ahlberg, Per
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p. 763 - 767
(2007/10/03)
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- A novel and one step procedure for preparation of α-bromo-α,β-unsaturated carbonyl compounds
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A new one step method is developed for the preparation of α-bromo-α,β-unsaturated carbonyl compounds in moderate to good yields from corresponding α,β-unsaturated carbonyl compounds using DMP [1,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-3(IH)-one] and te
- Ramanarayanan,Shukla, Vidyanand G.,Akamanchi
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p. 2059 - 2061
(2007/10/03)
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- A convenient and useful method of preparation of α-bromo enones from the corresponding enones using organic ammonium tribromide (OATB)
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Various acyclic α-bromo enones 2 as well as cyclic α-bromo enones 4 can be prepared from the corresponding acyclic enones 1 and cyclic enones 3 respectively, in a one-pot procedure by employing organic ammonium tribromide, such as cetyltrimethylammonium t
- Bose, Gopal,Bujar Barua, Pankaj M.,Chaudhuri, Mihir K.,Kalita, Dipak,Khan, Abu T.
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p. 290 - 291
(2007/10/03)
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- A mild preparation of α-halo-α,β-enones from cyclic enones
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A simple one pot procedure flor the selective transformation of cyclic enones into α-halo-α,β-enones is reported using dimethyldioxirane and metal halides/Amberlyst 15. The method appears particularly appealing for the preparation of labelled molecules for use with the CMIA technique.
- Righi, Giuliana,Bovicelli, Paolo,Sperandio, Anna
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p. 5889 - 5892
(2007/10/03)
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- Diastereoselective synthesis of a taxane precursor
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A highly diastereoselective synthesis of the taxane potential precursor 16 is achieved. An unexpected diastereoselectivity was observed upon condensation of the α-trimethylsiloxyaldehydes 9a or 9b with the cyclohexenyllithium 10. The single diol isomers 13A and 14A exhibiting the required 1β,2α relative configuration are obtained in good yields.
- Muller, Benoit,Delaloge, Francette,Den Hartog, Marc,Ferezou, Jean-Pierre,Pancrazi, Ange,Prunet, Joelle,Lallemand, Jean-Yves,Neuman, Alain,Prange, Thierry
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p. 3313 - 3316
(2007/10/03)
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- NOVEL TRANSFORMATIONS WITH BORONTRIFLUORIDE ETHERATE/IODIDE ION : FACILE CONVERSION OF 2-KETOOXIRANES AND 2-BROMO-2-ENONES TO THE α,β-UNSATURATED CARBONYL COMPOUNDS.
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Borontrifluoride etherate/iodide ion rapidly deoxygenates α-ketooxiranes, 3, to the corresponding α,β-unsaturated carbonyl compounds, 4, in near quantitative yields.In contrast, the reaction of 3 with borontrifluoride etherate/bromide ion, 2, yielded the corresponding 2-bromo-2-enone derivatives, 5, in excellent yields.The reagent 1, also dehalogenates a variety of 2-bromo-2-enones, 5, to the corresponding 2-en-1-one derivatives, 4, in high yields.
- Mandal, Arun K.,Mahajan, S. W.
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p. 2293 - 2300
(2007/10/02)
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- Synthetic Studies Aimed at the Dolastanes. An Attempted A + C -> ABC Approach
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The dolastanes are marine diterpenes whose molecular array of fused 6-7-5 alicyclic rings is distinctive.As part of a program directed toward the synthesis of representatives of these bioactive natural products, the possibility of elaborating their framework by intramolecular cyclization to form the central seven-membered ring has been examined.An expedient two-step route to keto ester 8 was developed.This intermediate proved receptive to copper-promoted conjugate addition of allylmagnesium bromide and lithium.The acetal 21 to be subsequently derived from these adducts could be conveniently crafted into the highly functionalized 2-cyclopentenones 27.Central to the synthetic strategy was the need for intramolecular C-C bond formation within 27.Because we were singularly unsuccessful in achieving the desired end result, this particular approach appears unsuited for gaining access to the dolastanes.
- Belmont, Daniel T.,Paquette, Leo A.
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p. 4102 - 4107
(2007/10/02)
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