1745-31-9Relevant academic research and scientific papers
DBU-mediated Ireland-Claisen rearrangement of allyl alk-3-enoates: an efficient synthesis of 2-ethylidene-γ,δ-unsaturated carboxylic acids
Li, Yunxia,Goeke, Andreas,Wang, Ruiyao,Wang, Quanrui,Fráter, Georg
, p. 9605 - 9613 (2007)
Ireland-Claisen rearrangement, triggered by silyl enolization of allylic but-3-enoates 2, has been developed using DBU as the base in the presence of an excess amount of TMSCl under reflux in acetonitrile for a couple of hours. The procedure allows the synthesis of a range of 2-ethylidene-γ,δ-unsaturated carboxylic acids 5 in moderate to high yields. It is further revealed that the rearrangement proceeds equally well with allylic (E)-hexa-3,5-dienoates 10 derived from sorbic acid under similar conditions to provide 2-allyl substituted hexa-2,4-dienoic acids 13.
Synthesis of 2,6-dideoxysugars via ring-closing olefinic metathesis.
Andreana, Peter R,McLellan, Jason S,Chen, Yongchen,Wang, Peng George
, p. 3875 - 3878 (2007/10/03)
[formula: see text] Grubbs' RuCl2 (=CHPh)(PCy3)2 (catalyst 1) and RuCl2(=CHPh)(PCy3)(IMess) (catalyst 2) complexes have been successfully utilized in the construction of beta,gamma-unsaturated delta-lactones containing various substitution patterns of methyl groups. Asymmetric dihydroxylation followed by reduction leads to 3,4-cis-dihydroxy-2,6-dideoxypyranoses, which have proven to play very important biological roles as key components of natural products.
An access to (Z)-ethylenic pseudodipeptides based on ring-closing metathesis
Boucard, Valérie,Sauriat-Dorizon, Hélène,Guibé, Fran?ois
, p. 7275 - 7290 (2007/10/03)
A new access to enantiopure (Z)-ethylenic pseudopeptides, starting from the chiral pool of amino acids and enantiopure 2-substituted-but-3-enoic acids is proposed and illustrated by the syntheses of the (Z)-ethylenic pseudopeptidic analogs of L-Phe-L-Phe, L-Phe-D-Phe, L-Phe-L-Val, L-Phe-D-Val and racemic (LL,DD) and (LD,DL) (phenyl)Gly-Phe. The key-steps of these syntheses are a ring-closing metathesis, catalysed by Grubbs' ruthenium alkykidene complexes, on diethylenic amides and the hydrolytic cleavage of the resulting dihydropyridones under mild conditions through intermediate formation of cyclic imidates.
Total syntheses of (-)-grandinolide and (-)-sapranthin by the sharpless asymmetric dihydroxylation of methyl trans-3-pentenoate: Elucidation of the stereostructure of (-)-sapranthin
Harcken, Christian,Brueckner, Reinhard,Rank, Elisabeth
, p. 2342 - 2352 (2007/10/03)
Methyl trans-3-pentenoate (7) was converted into the cis-substituted γ- lactone 8 in a single step with 78% ee. The derived enolate dilithio-8 was alkylated trans-selectively with primary iodoalkanes with 1-iodobutane dilithio-8 afforded, after esterification with isovaleroyl chloride, the epi- blastmycinone 9. Dilithio-8 gave (-)-grandinolide (II) with 1-iodo-19- phenylnonadecane (20). A third trans-selective alkylation of dilithio-8 was undertaken with 16-iodo-1,5-hexadecadiene-7,9-diyne (21). This gave the γ- 1actone 12, which had the published relative configuration of (-)-sapranthin but different spectroscopic data. When the OH group of lactone 8 was inverted (to hydroxylactone 40) and the derived enolate dilithio-40 alkylated with iodide 21, lactone 41 resulted. Its 1H and 13C NMR spectra and the sign and value of optical rotation coincide with the data of natural sapranthin. These findings establish that (-)-sapranthin possesses the relative and absolute configuration of stereoformula 41. The synthesis of iodide 21 was performed via the dienoic carboxylic ester trans-23 which stemmed from the Claisen-Ireland rearrangement (27 → 28/29)/esterification (28/29 → 26)/Cope rearrangement (26 → 23) sequence shown in Scheme 5.
The carbonylation of allylic halides and prop-2-en-1-ol catalysed by triethylphosphine complexes of rhodium
Payne, Marc J.,Cole-Hamilton, David J.
, p. 3167 - 3175 (2007/10/03)
In ethanol, [RhX(CO)(PEt3)2] added directly or formed in situ from [Rh2(OAc)4]·2MeOH (OAc = O2CMe) and PEt3 or [Rh(OAc)(CO)(PEt3)2] catalysed the carbonylation of CH2=CHCH2X (X = Cl, Br or I) to ethyl but-3-enoate with CH2=CHCH2OEt as a side product. Small amounts of the isomerisation product, ethyl but-2-enoate were produced but no base was required for the reaction. The selectivity of the reaction is in the order Cl > Br > I and prop-2-en-1-ol can be successfully carbonylated to prop-2-enyl but-3-enoate by the same system using 3-chloroprop-1-ene as a promoter. 3-Fluoropropene was not carbonylated, but in the presence of H2 underwent hydroformylation to produce acetals. 3-Chlorobut-1-ene and 1-chlorobut-2-ene both produced ethyl pent-3-enoate and 3-ethoxybut-1-ene. In situ and ex situ NMR and IR spectroscopic studies have been used to show that the first step of the reaction is oxidative addition to give [Rh(CH2CH=CH2)Cl2(CO)(PEt3) 2] for which thermodynamic parameters have been obtained. Both 3-chlorobut-1-ene and 1-chlorobut-2-ene give [Rh(CH2CH=CHMe)Cl2-(CO)(PEt3)2] but with different E:Z ratios. The detailed mechanism of the oxidative addition is discussed. The CO inserts into the Rh-C bond to give [Rh(COCH2CH=CH2)Cl2(CO)(PEt3) 2], from which but-3-enoyl chloride reductively eliminates to react with ethanol to give the observed products. High-pressure IR and high-pressure NMR studies reveal that [RhX(CO)(PEt3)2] (X = Cl or Br) reacts with CO to give [RhX(CO)2(PEt3)2], which exists as two isomeric forms. The compound [Rh(OAc)(CO)(PEt3)2] catalyses the formation of prop-2-enyl ethanoate from 1-chloroprop-2-ene and sodium ethanoate. A mechanism is proposed.
A VERSATILE ROUTE TO MIXED VINYLKETENE ACETALS : USE OF 1-t-BUTYLDIMETHYLSILOXY-1-ETHOXY BUTADIENE IN CYCLOHEXENONE SYNTHESIS
Lombardo, Luciano
, p. 381 - 384 (2007/10/02)
The successful entry to the diverse mixed vinylketene acetals 3 extends the participation of these intermediates in cyclohexenone synthesis.
Palladium-Catalyzed Decarboxylation-Carbonylation of Allylic Carbonates To Form β,γ-Unsaturated Esters
Tsuji, Jiro,Sato, Koji,Okumoto, Hiroshi
, p. 1341 - 1344 (2007/10/02)
Allyl alkyl carbonates undergo a smooth decarboxylation-carbonylation reaction to afford β,γ-unsaturated esters at 50 deg C under atmospheric or low pressure of carbon monoxide and neutral conditions in the presence of palladium-phosphine complexes as catalysts.The reaction offers a very good method for the preparation of β,γ-unsaturated esters from allylic alcohols.
PALLADIUM-CATALYZED DECARBOXYLATION-CARBONYLATION OF ALLYLIC CARBONATES TO GIVE β,Γ-UNSATURATED ESTERS UNDER MILD CONDITIONS
Tsuji, Jiro,Sato, Koji,Okumoto, Hiroshi
, p. 5189 - 5190 (2007/10/02)
Allylic carbonates undergo facile palladium-catalyzed decarboxylation-carbonylation under mild conditions to give β,γ-unsaturated esters in high yields using palladium-phosphine complex as a catalyst.
SYNGAS REACTIONS II. THE HOMOGENEOUS CATALYZED CARBONYLATION AND CYCLIZATION OF ALLYLIC SUBSTRATES
Knifton, John F.
, p. 223 - 236 (2007/10/02)
Carbon monoxide insertion and/or addition to allylic precursors may lead to the formation of both linear and cyclic carbonylation products.In examining these competing reaction paths, rhodium, platinum, palladium and nickel-based homogeneous catalysts have been developed which are particularly useful for the selective synthesis of γ-butyrolactam, N-alkyl-2-pyrrolidones, vinylacetate and phenylacetate esters and diesters from a variety of allylic and benzylic substrates.The extension of this catalysis to the carbonylation of certain vinylic and propargyl congeners hasalso been considered.
Preparation of allyl vinylacetate esters
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, (2008/06/13)
This invention relates to the preparation of allyl vinylacetate esters via the catalytic carbonylation of allylic alcohols. The esters are produced in good yield and selectivity using empirically selected 3-component homogeneous palladium dihalide catalysts consisting essentially of 1) palladium(II) halides stabilized with 2) one or more Group VB donor ligands, and 3) in combination with Group IVB metal halide cocatalysts such as tin(II) halides, tin(IV) halides and germanium(II) halides. An improvement in shorter reaction times, increased yields and selectivity over what has been reported in the literature has been found to be attributable to the use of applicant's catalysts rather than the catalysts used in the art.
