Stereoselective synthesis of pyrazolidinones via dipolar cycloaddition of azomethine imines with active esters under Lewis base catalysis is presented. The active esters are readily generated in situ from the corresponding acids. Products, which are obtained with excellent diastereocontrol and high enantioselectivity, contain along with the pyrazolidinone core also the tetrahydroisoquinoline st...

7-Aryl-1,3,5-cycloheptatrienes react intermolecularly with methylenecyclopropanes in a triple gold(I)-catalyzed reaction to form cyclopentenes. The same formal (4+1) cycloaddition occurs with cyclobutenes. Other precursors of gold(I) carbenes can also be used as the C1 component of the cycloaddition.

The [3+2] cycloaddition between various nitriles and sodium azide proceeds smoothly in the presence of zeolite and sulfated Zircona as effective catalyst and in the water and DMF/MeOH, to give the corresponding arylaminotetrazoles in good to high yields. The reaction most probably precedes through the in situ formation of a catalyst azide species, followed by a successive [3+2] cycloaddition wi...

For the first time [3 + 2] 1,3-cycloaddition of an ionized carbonyl ylide has been observed in gas phase ion-molecule reactions of CH2OCH2 (1) with several carbonyl compounds. The reaction, which competes with electrophilic addition that leads to net CH2 transfer, occurs across the CdO double bond of acetaldehyde and several acyclic ketones yielding ionized 4,4-dialkyl-1,3-dioxolanes as unstabl...

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 potential energy surfaces of the cycloaddition reactions MO(4)(NC(5)H(5))(2) + C(60)→ MO(4)(NC(5)H(5))(2)(C(60)) (M = Fe, Ru, and Os) have been studied at the B3LYP/LANL2DZ level of theory. It has been found that there should be two competing pathways in these reactions, which can be classified as a [6,5]-attack (path A) and a [6,6]-attack (path B). Our theoretical calculations indicate tha...

A catalytic amount of tin(IV) chloride catalyzed formal [4+2] cycloaddition reaction of di-tert-butyl 2-ethoxycyclobutane-1,1-carboxylate with ketones or aldehydes to give diethyl 6-ethoxydihydro-2H-pyran-3,3(4H)-dicarboxylates, whereas two equivalents of trimethylsilyl triflate promoted tandem [4+2] cycloaddition and lactonization to afford 3-oxo-2,6-dioxabicyclo[2.2.2]octane-4-carboxylate est...

The aza-Diels-Alder cycloaddition of 1,2,4-triazines with alkynes offers a rapid and convenient method for the synthesis of highly substituted pyridines, but often requires harsh conditions and long reaction times. The present study offers a solution to these limitations by use of a temporary tether established by a Lewis acid-base complexation of in situ generated alkynylboranes and triazines ...