A highly diastereo- and chemoselective intramolecular nickel-catalyzed cycloaddition of alkene- and alkyne-tethered alkynylidenecyclopropanes is reported. The method constitutes the first fully intramolecular [3 + 2 + 2] alkylidenecyclopropropane cycloaddition occurring via a proximal cleavage of the cyclopropane and makes it possible to build relevant 6,7,5-tricyclic frameworks in a single-pot...

Pyridoxine reaction with (1)O(2) in aqueous solution at neutral pH resulted in oxidation at the 2- and 6-positions of the pyridine ring and unprecedented ring contraction. Kinetic and low temperature studies provided observable intermediates by NMR spectroscopy. In addition, novel cycloaddition between pyridoxine and N-methylmaleimide, without N-alkylation and in water, suggest a common [3 + 2]...

Cycloaddition reactions involving tetrazines have proven to be powerful bioorthogonal tools for various applications. Conceivably, sequential and selective labeling using tetrazine-based reactions can be achieved by tuning the reaction rate. By varying the substituents on tetrazines, cycloaddition rate variations of over 200 fold have been achieved with the same dienophile. Upon coupling with d...

Key words iridium catalysis - chiral phosphoric acid photocatalyst 2+2 cycloaddition

Isoxazolino[4,5:1,2][60]- and -[70]fullerenes undergo an efficient retro-cycloaddition reaction to pristine fullerene by thermal treatment in the presence of an excess of a dienophile and Cu(II) catalysis, which can be selectively used in the presence of malonate or pyrrolidine cycloadducts. Trapping experiments using N-phenylmaleimide as dipolarophile have shown that the reaction mechanism occ...

Articles you may be interested in Adsorption mechanisms of isoxazole and oxazole on Si(100)-2 × 1 surface: Si–N dative bond addition vs. [4+2] cycloaddition J. The adsorption configuration of furan on Si͑100͒-2ϫ1 at 125 K has been investigated using x-ray photoelectron spectroscopy ͑XPS͒, ultraviolet photoelectron spectroscopy ͑UPS͒, high resolution electron energy loss spectroscopy ͑HREELS͒, and semie...

The reaction pathways for the photochemical formation of cyclobutane thymine dimers in DNA are explored using hybrid density functional theory techniques. It is concluded that the thymine-thymine [2 + 2] cycloaddition displays favorable energy barriers and reaction energies in both the triplet and the singlet excited states. The stepwise cycloaddition in the triplet excited state involves the i...

The [3 + 2] cycloaddition reaction of 2-arylthiocarbamoyl benzimidazolium, -imidazolinium, and -triazolium inner salts (the ambident C-C-N and C-C-S 1,3-dipoles derived from carbenes) with ketenes proceeded efficiently in a highly site-selective manner to produce the C-C-N cycloaddition products benzimidazoline-, imidazolidine-, or triazoline spiro-pyrrolidones in 58-93% yields. Theoretical cal...

Sceptrins and nakamuric acid are structurally unique antibiotics isolated from marine sponges. Recent studies suggest that the biosynthesis of these dimeric pyrrole-imidazole alkaloids involves a single-electron transfer (SET)-promoted [2+2] cycloaddition to form their cyclobutane core skeletons. We describe herein the biomimetic syntheses of racemic sceptrin and nakamuric acid. We also report ...

An efficient and rapid synthesis of the CDEF ring system of lactonamycinone is reported via a highly chemo- and diastereoselective intermolecular Diels-Alder cycloaddition between trans-1,2-disilyloxybenzocyclobutene and the appropriate γ-alkylidenebutenolide. The feasibility and the total chemoselectivity of the [4 + 2] cycloaddition for the construction of a spirolactone moiety via an intramo...