Results 21 to 30 of about 7,931 (260)

Synthesis of novel pyrazoles via [2+3]-dipolar cycloaddition using alkyne surrogates [PDF]

Tetrahedron Letters, 2010
The syntheses of an important class of hitherto unreported novel pyrazoles are described. The regioselective synthesis of 1,3,4,5-tetrasubstituted pyrazoles was achieved by the Huisgen cyclization of nitrile imines with a trisubstituted bromoalkene. The substituted bromoalkene functions as an alkyne synthon which was used to construct 5,5-disubstituted
Sureshbabu, Dadiboyena, Edward J, Valente, Ashton T, Hamme   +2 more
openaire   +2 more sources

Facile generation of bridged medium-sized polycyclic systems by rhodium-catalysed intramolecular (3+2) dipolar cycloadditions

Nature Communications, 2021
The bridged medium-sized ring bicyclo[m.n.2] family of natural products are commonly found but difficult to synthesize efficiently. Here the authors present a cascade reaction to form the carbon skeleton, via a [3+2] cycloaddition of a captured azavinyl ...
Bao-Long Hou, Jonathan J. Wong, Na Lv, Yong-Qiang Wang, K. N. Houk, Chuang-Chuang Li   +5 more
doaj   +1 more source

1,3-Dipolar cycloadditions of 2-thio-3-chloroacrylamides with diazoalkanes [PDF]

, 2010
2-Thio-3-chloroacrylamides undergo 1,3-dipolar cycloadditions with diazoalkanes leading to a series of novel pyrazolines and pyrazoles. The mechanistic and synthetic features of the cycloadditions to the 2-thio-3-chloroacrylamides at both the sulfide and
Kissane, Marie, Lawrence, Simon E., Maguire, Anita R.   +2 more
core   +1 more source

Arylthio-substituierte Nitrilylide aus der Thermolyse von 4-Arylthio-3-oxazolin-5-onen

CHIMIA, 1984
Thermolysis of 4-arylthio- and 4-benzylthio-3-oxazolin-5-ones leads to arylthio- and benzylthio-substituted nitrile ylides, which undergo 1,3-dipolar cycloadditions with reactive dipolarophiles to give 5-membered aza-heterocycles (Schemes 1 and 2).
Peter Wipf, Heinz Heimgartner
doaj   +1 more source

Huisgen [3 + 2] Dipolar Cycloadditions of Phthalazinium Ylides to Activated Symmetric and Non-Symmetric Alkynes

Molecules, 2020
We present herein a straightforward and efficient pathway for the synthesis of pyrrolophthalazine cycloadducts via Huisgen [3 + 2] dipolar cycloaddition reactions of phthalazinium ylides to methyl propiolate or dimethyl acetylenedicarboxylate (DMAD).
Vasilichia Antoci, Costel Moldoveanu, Ramona Danac, Violeta Mangalagiu, Gheorghita Zbancioc   +4 more
doaj   +1 more source

Copper- and Silver-Catalyzed Reactions of Active Methylene Isocyanides: Facile Access to Highly Substituted Five- and Six-Membered Heterocycles. [PDF]

Chemistry
This review summarizes recent advances in copper‐ and silver‐catalyzed reactions of active methylene isocyanides for the synthesis of highly substituted five‐ and six‐membered heterocycles. Emphasis is placed on [3+n] cycloadditions, annulations, and asymmetric strategies, highlighting current limitations and future opportunities in heterocycle ...
George J, Oh K.
europepmc   +2 more sources

Intramolecular Azide to Alkene Cycloadditions for the Construction of Pyrrolobenzodiazepines and Azetidino-Benzodiazepines [PDF]

, 2014
The coupling of proline- and azetidinone-substituted alkenes to 2-azidobenzoic and 2-azidobenzenesulfonic acid gives precursors that undergo intramolecular azide to alkene 1,3-dipolar cycloadditions to give imine-, triazoline- or aziridine-containing ...
Antonow, Broggini, Christopher Chambers, Faisal Jamshaid, Karl Hemming, Mitra, Patel, Paul O'Gorman, Rahman, Thurston   +9 more
core   +2 more sources

Orthogonal, metal-free surface modification by strain-promoted azide–alkyne and nitrile oxide–alkene/alkyne cycloadditions [PDF]

, 2012
In this article we present a fast and efficient methodology for biochemical surface patterning under extremely mild conditions. Micropatterned azide/benzaldoxime-surfaces were prepared by microcontact printing of a heterobifunctional cyclooctyne oxime ...
Arlinghaus, Heinrich F, Burley, Glenn A, Ravoo, Bart Jan, Rinnen, Stefan, Schulz, Christian, Singh, Ishwar, Wendeln, Christian   +6 more
core   +1 more source

1, 3-Dipolar Cycloadditions. LXXVI. Cycloadditions of Diazomethane to Substituted Butadienes

Chemical and Pharmaceutical Bulletin, 1975
1-Substituted butadienes (R=CH2, CH3, O, C3H5, CO2CH3, CN) and 2-phenylbutadiene accept diazomethane at the 3, 4-bond yielding 3-vinylpyrazoline derivatives. Tautomerization of the 1-to 2-pyrazolines takes place either at room temperature (R=CO2CH3, CN), on heating (R=C6H5) or on acid catalysis (R=H, CH3, OCH3) ; the 2-pyrazolines are characterized as ...
ROLF HUISGEN, AKIHIRO OHTA, JOCHEN GEITTNER   +2 more
openaire   +2 more sources

1,3-Dipolar cycloadditions of 2-thio-3-chloroacrylamides with nitrile oxides and nitrones [PDF]

, 2010
1,3-Dipolar cycloadditions of 2-thio-3-chloroacrylamides with nitrile oxides and nitrones is described. A series of novel isoxazolines are isolated from the nitrile oxide cycloadditions, whilst the isoxazolines generated from the nitrone cycloadditions ...
Kissane, Marie, Lawrence, Simon E., Maguire, Anita R.   +2 more
core   +1 more source