The validity of calculated NMR shifts to predict the outcome of electrophilic aromatic substitution reactions on different heterocyclic compounds has been examined. Based on an analysis of >130 literature examples, it was found that the lowest predicted (13)C and/or (1)H chemical shift of a heterocycle correlates qualitatively with the regiochemical outcome of halogenation reactions in >80% of ...

The title compound, C(20)H(23)N(3)O(4)S, is an important biologically active heterocyclic compound. The five-membered ring is oriented with respect to the six-membered rings at dihedral angles of 78.60 (3) (trimethoxyphenyl ring) and 71.57 (3)° (methoxyphenyl ring). In the crystal structure, inter-molecular N-H⋯O hydrogen bonds link the mol-ecules into infinite chains along the c axis.

The importance of unsymmetrical N-heterocyclic carbenes (uNHCs) as ligands in metal-catalyzed reactions is undeniable. While uNHCs show similar properties as compared with symmetrical NHCs, dissymmetrization allows for further fine-tuning. The introduction of chelatization, hemilability, bifunctionality, shielding effects, and chirality-transfer influences the catalyst's stability, reactivity, ...

A highly efficient and straightforward three-component cascade reaction was developed to synthesize benzo[g]imidazo[1,2-a]quinolinedione derivatives from heterocyclic ketene aminals (HKAs), aldehydes, and 2-hydroxy-1,4-naphthoquinone (HNQ) via Et(3)N-catalyzed tandem [3 + 2 + 1] annulation under solvent-free conditions. The reactions were very mild, convenient and highly regioselective to form ...

In the context of research in the broad area of nutrition and cancer, a major new discovery was made during 1976, quite recently, when T. Sugimura (National Cancer Center, Tokyo, Japan) observed the un expected presence of considerable mutagenicity at the surface of grilled or broiled fish or meat, using the usual procedures of cooking such foods. Isolation and identification of the mutagens sh...

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Cross-coupling of aromatic aldehydes or benzoins with unactivated imines catalyzed by an N-heterocyclic carbene (NHC) affords alpha-amino ketones smoothly.

The aromaticity of some bicyclic heterocycles is discussed with the aid of the configuration analysis of the expansion coefficient matrices and the similarity analysis of the density matrices. The iso-it-electronic [9] annulenyl anion is taken as the aromatic reference compound for all the heterocyclic compounds considered. The restflts are compared with · those previously obtained from conside...

Homoenolates generated from enals by nucleophilic heterocyclic carbene (NHC) catalysis undergo a conjugate addition/cyclization sequence with cyclic dienones, culminating in the efficient synthesis of spirocyclopentanones.

Recent investigations have shown the oxone-mediated oxidative methyl esterification of benzaldehyde derivatives using methanol. The reactions were accelerated in the presence of indium(III) triflate, a trivalent indium reagent, in many cases. Based on this method of methyl esterification of benzaldehyde derivatives, we further explored an application to heterocyclic aldehydes. The reactions wer...