- Chemoselective Biohydrogenation of Alkenes in the Presence of Alkynes for the Homologation of 2-Alkynals/3-Alkyn-2-ones into 4-Alkynals/Alkynols
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The chemoselective hydrogenation of alkenes in the presence of alkynes is a very challenging transformation to achieve with traditional chemical methods. The development of an effective procedure to perform this transformation would enrich the tool-kit available to organic chemists for the development of useful synthetic routes, and the creation of novel structural motifs. The reduction of activated alkene bonds by ene-reductases (ERs) is completely chemoselective, because of the mechanism of the reaction. Thus, we investigated the use of ERs belonging to the Old Yellow Enzyme family for the reduction of α,β-unsaturated aldehydes with a conjugated C≡C triple bond at the γ position. This reaction was exploited as the key step for the development of an effective homologation route to convert aryl and alkyl substituted propynals and butynones into 4-alkynals and 4-alkynols, avoiding some troublesome or hazardous steps of known synthetic routes. (Figure presented.).
- Colombo, Danilo,Brenna, Elisabetta,Gatti, Francesco G.,Ghezzi, Maria Chiara,Monti, Daniela,Parmeggiani, Fabio,Tentori, Francesca
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p. 2638 - 2648
(2019/05/16)
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- A new Co2(CO)8-mediated tandem [5 + 1]/[2 + 2 + 1]-cycloaddition reaction: A one-pot synthesis of tricyclic δ-lactones from cis-epoxy ene-ynes
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In the presence of Co2(CO)8 and CO, cis-epoxyalkynes bearing a tether olefin undergo a tandem [5 + 1]/[2 + 2 + 1]-cycloaddition to give tricyclic δ-lactones efficiently in a one-pot operation. The reaction mechanism is proposed to in
- Odedra, Arjan,Wu, Chang-Jung,Madhushaw, Reniguntala J.,Wang, Su-Lein,Liu, Rai-Shung
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p. 9610 - 9611
(2007/10/03)
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- A general and facile synthesis of substituted furans by palladium- catalyzed cycloisomerization of (Z)-2-en-4-yn-1-ols
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A general and facile synthesis of furans, based on Pd(II)-catalyzed cycloisomerization of (Z)-2-en-4-yn-1-ols, is described. Cycloisomerization reactions are carried out at 25-100 °C in the presence of a very simple catalytic system, consisting of K2PdI4, under essentially neutral conditions. This new methodology is very versatile and can be applied to the synthesis of a variety of substituted furans, including particularly fragile, naturally occurring furans such as rosefuran. Efficient synthetic approaches for the regioselective synthesis of suitably substituted (Z)-2-en-4-yn-1-ols have been developed.
- Gabriele,Salerno,Lauria
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p. 7687 - 7692
(2007/10/03)
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- The first 1,7-electrocyclizations of butadienyl pyridinium ylides: Stereoselective formation of 1,2-annulated 2,3-dihydroazepines
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Upon deprotonation of pentadienyl substituted pyridinium bromides 6/13, conjugated azomethine ylide-type dipoles are formed which undergo stereoselective 8π-electrocyclization affording 10,10a-dihydropyrido[1,2-a]-azepines 8a-k and 15a,b, respectively.
- Marx, Karsten,Eberbach, Wolfgang
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p. 14687 - 14700
(2007/10/03)
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- Synthesis of Furans by Cyclization of 2-En-4-yn-1-ols in the Presence of Ruthenium and Palladium Catalysts
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Substituted furans have been synthesized in the presence of ruthenium catalysts under neutral and mild conditions via cyclization of primary and secondary enynols of type (Z)-HCC-C(Me)=CH-CH(R)OH containing a terminal triple bond.The intramolecular addition of the hydroxy group to the triple bond of internal (Z)-enynols is also possible upon palladium catalysis.
- Seiller, Benedicte,Bruneau, Christian,Dixneuf, Pierre H.
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p. 13089 - 13102
(2007/10/02)
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- HIGHLY STEREOSELECTIVE AND GENERAL SYNTHESIS OF (Z)-3-METHYL-2-ALKEN-1-OLS VIA PALLADIUM-CATALYZED CROSS COUPLING OF (Z)-3-IODO-2-BUTEN-1-OL WITH ORGANOZINCS AND OTHER ORGANOMETALS
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The reaction of Zn-protected (Z)-3-iodo-2-buten-1-ol with organozincs in the presence of 1-5 mol percent of a Pd complex, e.g., Pd(PPh3)4 or Cl2Pd(PPh3)2 and n-BuLi (2 equiv), in DMF provides a highly stereoselective (>/= 96 percent), general, and high-yi
- Negishi, Ei-ichi,Ay, Mehmet,Gulevich, Yuri V.,Noda, Yumiki
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p. 1437 - 1440
(2007/10/02)
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