- Intramolecular Cyclization of Vinyldiazoacetates as a Versatile Route to Substituted Pyrazoles
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Vinyldiazo compounds undergo a thermal electrocyclization to form pyrazoles in yields of up to 95percent. The reactions are operationally simple, use readily available starting materials, require no intervention of a catalyst, and enable the synthesis of mono-, di- A nd tri-substituted pyrazoles. With the ability to produce highly substituted pyrazoles and the flexibility in installing various types of substituents, this method constitutes a new entry to this valuable heterocyclic scaffold and may be of interest to all branches of the chemical industry.
- Drikermann, Denis,G?rls, Helmar,Kerndl, Valerie,Vilotijevic, Ivan
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p. 1158 - 1162
(2020/07/20)
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- Synthesis of Allylboranes via Cu(I)-Catalyzed B-H Insertion of Vinyldiazoacetates into Phosphine-Borane Adducts
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Cu(I) catalysts enable C-B bond formation via direct insertion of vinyldiazoacetates into B-H bonds of borane-phosphine Lewis adducts to form phosphine-protected allylboranes under mild conditions. The resulting allylborane-phosphine Lewis adducts can be used in the diastereoselective allylation of aldehydes directly without the need for removal of the phosphine. The allylation reaction proceeds with high diastereoselectivity and yields 5,6-disubstituted dihydropyranones after treatment with an appropriate acid.
- Drikermann, Denis,M??el, Robert S.,Al-Jammal, Walid K.,Vilotijevic, Ivan
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supporting information
p. 1091 - 1095
(2020/02/15)
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- Synthesis of Optically Active Butenolides and γ-Lactones by the Sharpless Asymmetric Dihydroxylation of β,γ-Unsaturated Carboxylic Esters
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Keywords: asymmetric synthesis; butenolides; dihydroxylations; furanones; lactones
- Harcken, Christian,Brueckner, Reinhard
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p. 2750 - 2752
(2007/10/03)
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- Formation of Unsaturated Esters in the Single Electron Transfer Reaction of Cyclopropanone Acetals with Quinones under Non-irradiated Conditions
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Unsaturated esters were formed from cyclopropanone aceytals in the reaction with DDQ or chloranil, where ring-opened C-C and C-O bonded adducts were the intermediates formed via a SET mechanism resulting in the ester formation.
- Abe, Manabu,Oku, Akira
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p. 3551 - 3554
(2007/10/02)
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- A convenient route for the homologation of saturated esters to α,β-unsaturated esters
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Methyl hexanoate (1a) is transformed to methyl 2-hydroxyheptanoate (5a) employing the following sequence of reactions (Scheme 1); (i) reaction with sodium hydride-dimethyl sulfoxide, (ii) Pummerer rearrangement with acetic anhydride-sodium acetate, (iii) alkaline hydrolysis and (iv) esterification with diazomethane.The α-hydroxy ester (5a) is converted into methyl 2E-heptenoate (7a) employing the following reactions (Scheme 2); (i) reaction with phosphorous tribromide and (ii) elimination using DBU.Thus, the sequence of reactions given in Schemes 1 and 2 provide aconvenient route for the one carbon homologation of saturated esters to α,β-unsaturated esters.
- Mohan, H Rama,Rao, A S
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p. 698 - 700
(2007/10/02)
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- PHEROMONES OF INSECTS AND THEIR ANALOGS XXXIII. SYNTHESIS OF HEXADEC-7Z,11E-DIEN-1-YL ACETATE - THE SEX PHEROMONE OF Sitotroga cerealella AND A COMPONENT OF THE SEX PHEROMONE OF Pectinophora gossypiella
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From cyclohexene and caproaldehyde, using ozonolysis and the Knoevenagel reaction, we have synthesized hexadeca-7Z,11E-dien-1-yl acetate - the sex pheromone of Sitotroga cerealella and a component of the sex pheromone of Pectinophora gossypiella.
- Odinokov, V. N.,Ishmuratov, G. Yu.,Ladenkova, I. M.,Botsman, L. P.,Kargapol'tseva, T. A.,Tolstikov, G. A.
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p. 621 - 623
(2007/10/02)
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- Prostaglandins and Prostaglandin Intermediates. 22 - Synthesis of a Stable Prostacyclin Analogue
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An industrially available prostaglandin intermediate is converted into a new prostacyclin analogue with a cyclic ether instead of the unstable enol ether system.For the construction of the modified alkyl side chain two subsequent Horner olefinations are used.This reaction sequence includes a new methodology for the conversion of an aldehyde into a β,γ-unsaturated carboxylic acid by a three-carbon elongation.
- Theil, F.,Costisella, B.,Hauser, A.,Schick, H.,Schwarz, S.
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p. 766 - 774
(2007/10/02)
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- SYNTHESIS OF CARBOXYLIC ESTERS USING FORMALDEHYDE DIMETHYL DITHIOACETAL S,S-DIOXIDE
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Formaldehyde dimethyl dithioacetal S,S-dioxide (1) reacted with an alkyl bromide or a 2-alkenyl bromide (8) under phase-transfer conditions using 50percent aq.NaOH to give an alkyl or 2-alkenyl derivative of 1, whereas, in the reaction with 8 in the presence of K2CO3-KI in HMPA, 1 formed a 1-alken-3-yl derivative.Transformation of these products into the corresponding carboxylic esters was also described.
- Ogura, Katsuyuki,Watanabe, Jun-ichi,Iida, Hirotada
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p. 4499 - 4502
(2007/10/02)
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