Search results for "Cycloaddition"

Pyrene-benzoylthiophene exciplexes as selective catalysts for the [2+2] cycloaddition between cyclohexadiene and styrenes.

2007

Efficient intramolecular fluorescence quenching in pyrene−benzoylthiophene systems leads to formation of exciplexes. These species interact with 1,3-cyclohexadiene (or styrenes), leading to reactive excited triplexes. The overall process affords [2+2] cross-cycloadducts with an average yield of 57%.

A DFT study of the [3 + 2] versus [4 + 2] cycloaddition reactions of 1,5,6-trimethylpyrazinium-3-olate with methyl methacrylate.

2013

The reaction between 1,5,6-trimethylpyrazinium-3-olate and methyl methacrylate (MMA) yielding a lactone-lactam has been studied using the DFT method at the B3LYP/6-31G(d) level. It is concluded that formation of the lactone-lactam is a domino process involving three consecutive reactions: (i) a 1,3-dipolar cycloaddition (13DC) reaction between the pyrazinium-3-olate and MMA yielding a [3 + 2] cycloadduct (CA); (ii) a skeletal rearrangement, which converts the [3 + 2] CA into a formal [4 + 2] CA, possessing a diazabicyclo[2.2.2]octane structure; and finally, (iii) an S(N)2 reaction, promoted by halide anion, with concomitant nucleophilic attack of the created carboxylate anion on an iminium …

ChemInform Abstract: Modular One-Pot Synthesis of Tetrasubstituted Pyrroles from α-(Alkylideneamino)nitriles.

2008

2,3,4,5-Tetrasubstituted pyrroles have been prepared with high regioselectivity by a formal cycloaddition of α-(alkylideneamino)nitriles and nitroolefins followed by elimination of HCN and HNO2. The reaction allows the convergent construction of the pyrrole ring in four steps from a nitroalkane and three aldehydes.

Photochemical generation of benzene–naphthalene biplanemers

2005

Abstract A direct biplanemer synthesis could be achieved by a quantitative [4π+4π]photocycloaddition of benzyloxy substituted benzene and naphthalene rings ( 3d , e  ⇄  4d , e ). Since the products do not show a thermal Cope rearrangement—in contrast to the related longicyclic conjugated 9,10-benzotricyclo[4.2.2.2 2,5 ]dodeca-3,7,9-trienes—but a quantitative reverse reaction, they are interesting systems for an optical switching.

Cycloaddition Reactions in Organic Synthesis. VonW. Carruthers. Pergamon Press, Oxford 1990. VIII, 373 S., Paperback $ 30.00. - ISBN 0-08-034712-6

1991

Highly Enantio- and Diastereoselective Inverse Electron Demand Hetero-Diels-Alder Reaction using 2-Alkenoylpyridine N-Oxides as Oxo-Heterodienes

2008

A general catalytic inverse electron demand hetero-Diels Alder reaction for 2-alkenoylpyridine N-oxides is presented. 2-Alkenoylpyridine N-oxides react very efficiently with alkenes in the presence of bisoxazolidine-copper(II) [BOX-Cu(II)] complexes to give chiral dihydropyrans bearing a pyridine ring at the 6-position with very high yields and excellent diastereo- and enantioselectivity. These heterodienes exhibited higher reactivity and enantioselectivity than the corresponding non-oxidized 2-alkenoylpyridines.

E-Ring extended estrone derivatives: introduction of 2-phenylcyclopentenone to the estrone D-ring via an intermolecular Pauson–Khand reaction

2006

Abstract An expedient synthetic route to E-ring extended estrone derivatives is reported. Estrone-derived cyclopentenones were accessed by an intermolecular Pauson–Khand (PK) cycloaddition. It was found that electron donating and withdrawing substituents in the arylalkyne increased and decreased the yields of PK products, respectively. The stereochemistry of the products was elucidated by X-ray and NMR studies.

ChemInform Abstract: Total Synthesis of (.+-.)-Scopolamine: Challenges of the Tropane Ring.

2016

Scopolamine was synthesized using 6,7-dehydrotropine as a key intermediate. Rhodium-catalyzed [4 + 3] cycloaddition chemistry and a modified Robinson–Schopf reaction were each independently evaluated for their utility in constructing the tropane core. Both synthetic approaches gave comparable overall yields.

An Overview on the Performance of 1,2,3-Triazole Derivatives as Corrosion Inhibitors for Metal Surfaces

2021

This review accounts for the most recent and significant research results from the literature on the design and synthesis of 1,2,3-triazole compounds and their usefulness as molecular well-defined corrosion inhibitors for steels, copper, iron, aluminum, and their alloys in several aggressive media. Of particular interest are the 1,4-disubstituted 1,2,3-triazole derivatives prepared in a regioselective manner under copper-catalyzed azide-alkyne cycloaddition (CuAAC) click reactions. They are easily and straightforwardly prepared compounds, non-toxic, environmentally friendly, and stable products to the hydrolysis under acidic conditions. Moreover, they have shown a good efficiency as corrosi…

Crystal structure of 5-(4-tert-butoxyphenyl)-3-(4-n-octyloxyphenyl)-4,5-dihydroisoxazole

2019

The molecule of the title compound, C27H37NO3, was prepared by [3 + 2] 1,3-dipolar cycloaddition of 4-n-octylphenylnitrile oxide and 4-tert-butoxystyrene, the latter compound being a very useful intermediate to the synthesis of liquid-crystalline materials. In the molecule, the benzene rings of the n-octyloxyphenyl and tert-butoxyphenyl groups form dihedral angles of 2.83 (7) and 85.49 (3)°, respectively, with the mean plane of the isoxazoline ring. In the crystal, molecules are linked by weak C—H...O hydrogen interactions into chains running parallel to the b axis.