Aromatic and aliphatic oximes have been deoximated in chloroform-water to the corresponding aldehydes with dilute hydrogen peroxide and triscetylpyridinium tetrakis (oxodiperoxotungsto) phosphate as catalyst. The presence of dipolarophiles in the reaction mixtures allows a competitive reaction that converts oximes into isoxazole and isoxazoline derivatives via the intermediate formation of nitr...

Elucidation of mechanisms and discovery of novel reactions are interconnected, as four research chapters from the Munich laboratory demonstrate. 1) In a new opening of the furan ring, 2-methoxyfuran and tetra-acceptor-substituted ethylenes furnish methyl acrylates, which are cis-3-substituted by a cyclopropyl ring that bears the four acceptor groups. Experiments with trans- and cis-1,2-bis(trif...

The principle of hard and soft acids and bases is applied in the local sense to rationalize the regiochemistry in the cycloaddition reactions of a few typical 1,3-dipoles, in particular those with phosphorus-containing dipolarophiles. Local softnesses are calculated using density functional theory. It is observed that the regioselectivity can be explained using these new reactivity descriptors ...

[reaction: see text] A general strategy for highly enantioselective 1,3-dipolar cycloaddition of diazoesters to beta-substituted, alpha-substituted, and alpha,beta-disubstituted alpha,beta-unsaturated pyrazolidinone imides is described. Cycloadditions utilizing less reactive alpha,beta-disubstituted dipolarophiles require elevated reaction temperatures, but still provide the corresponding pyraz...

The scope of applications of dialkyl dicyanofumarates and maleates as highly functionalized electron-deficient dipolarophiles, dienophiles and Michael acceptors is summarized. The importance for the studies on reaction mechanisms of cycloadditions is demonstrated. Multistep reactions with 1,2-diamines and β-aminoalcohols leading to diverse five- and six-membered heterocycles are discussed. Appl...

1,3-Dipolar cycloaddition of azomethine ylides derived from acenaphthylene-1,2-dione and 5methyl-benzo[b]-thiophene-2,3-dione with L-proline, thiazolidine-4-carboxylic acid and 1,2,3,4tetrahydroisoquinoline-3-carboxylic acid with various electron deficient dipolarophiles leads to the formation of novel spiroheterocycles having two or more chiral centers. Semiempirical studies have been performe...

Indoles substituted by electron-depleted thio groups at positions 1 and 3 react as C2 = C3 dipolarophiles with an electron-rich azomethine ylide dipole under flow conditions. The dearomatizing (3 + 2) cycloadditions readily occur to afford the corresponding fluorinated 3D-pyrrolidinoindolines bearing a tetrasusbtituted carbon centre ring junction.

Preparation of a series of terminally and internally substituted delta-alkenyl and delta-alkynyl esters 6, 7 and 9, potential precursors to oxazin-2-one nitrones, has been attempted. Condensation between pyruvic or benzoylformic acid and the appropriate alcohol proceeded smoothly in some cases whilst allylic transposition was a major feature in other cases--most especially during reactions with...

a series of 1,3-dipolar cycloaddition reactions are carried out using cyclodimers of simple nitrones and various dipolarophiles; substituted isoxazolidines are isolated and identified. it is proved that such cyclodimers, in solution, are in equilibrium with their corresponding nitrones and enamines. it is also concluded that aldocyclodimers are more potent than keto-cyclodimers in establishing ...