Laccase-catalyzed oxidation of substituted catechols followed by reaction with 4-hydroxy-pyrone/-benzopyrone afforded substituted benzofuran regioisomers whose structures with only two aromatic protons in total prevent a rapid structural assignment. Based on the evaluation of (1)H-(13)C long-range coupling constants a rule of thumb could be deduced for an easy and unambiguous differentiation between the possible regioisomers formed. DFT frontier orbital calculations of the reactants offer an interesting tool to explain the regioselectivity of the key reaction.

AbstractThe one‐pot synthesis of benzimidazoles (III) involves condensation of o‐phenylenediamine with aldehydes, cyclization of the resulting Schiff bases and subsequent laccase‐promoted aerobic oxidation of the intermediate benzimidazoline derivatives.

The laccase-catalyzed domino reaction of o-phenylenediamine and benzaldehydes with aerial oxygen as the oxidant exclusively yields 2-aryl-1H-benzimidazoles in good to very good yields. It is easy to perform under very mild reaction conditions.

The laccase-catalyzed reaction between catechols and heterocyclic 1,3-dicarbonyls (pyridinones, quinolinones, thiocoumarins) using aerial oxygen as the oxidant delivers benzofuropyridinones, benzofuroquinolinones, and thiocoumestans in a simple fashion, highly regioselectively with yields ranging from 55 to 98%. With barbituric acid derivatives the exclusive formation of dispiropyrimidinone derivatives takes place. The unambiguous and complete structure elucidation of all reaction products has been achieved by means of NMR spectroscopic methods (HSQMBC and band-selective HMBC) as well as by X-ray crystal structure analysis.

The enzymes tyrosinase and laccase from a crude extract of the button mushroom (Agaricus bisporus) can be employed to catalyze the domino reaction between phenol and various cyclic 1,3-dicarbonyls using atmospheric oxygen as the oxidizing agent and yielding annulated benzofuranes in a highly efficient and sustainable manner.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A range of new 7-phenyl-2H,5H-pyrano[4,3-b]pyran-5-ones and related tricyclic heterocycles was prepared in a single step by means of a domino Knoevenagel condensation/6π-electron electrocyclization under different reaction conditions, including thermal and microwave conditions. The influence of several ionic liquids as solvents was also studied

A range of new 7-plieiiyl-2H,5H-pyrano[4,3-b]pyran-5-ones and related tricyclic heterocycles was prepared in a single step by means of a domino Knoevenagel condensation/6 pi-electron electrocyclization under different reaction conditions, including thermal and microwave conditions. The influence of several ionic liquids as solvents was also studied.

New methano[1,5]dioxocines, O-heterocycles with a framework similar to Tröger’s base, were prepared by means of a three-component reaction. The scope of this domino reaction was studied.

The process of the cationic olefin cyclization of 3-sub-stituted 4-hydroxy-2 H-pyran-2-ones 3 that may produce both TRANS- and CIS-pyrano[4,3- B]chromen-1-ones ( 4) and TRANS- and CIS-pyrano[2,3- B]chromen-4-ones ( 5) can be efficiently controlled by properly choosing reagents and reaction conditions. The highly -selective formation of TRANS- 4 can be achieved with Et 2AlCl as a Lewis acid. Preferred formation of CIS- 4 is observed with PTSA -under microwave conditions at high temperatures. PTSA and low temperatures produce CIS- 5 in excess.

Substituted 7-methyl-2H,5H-pyrano[4,3-b]pyran-5-ones and related heterocycles 3 were synthesized through an efficient domino Knoevenagel condensation/6 pi-electron electrocyclization. In vitro antiproliferative/cytotoxic activity evaluation was performed with human SH-SY5Y neuroblastoma cells and revealed IC50 values ranging from 6.7 to > 200 mu M. The compound that was most cytotoxic to the neuroblastoma cells, that is, 2-isobutyl-3-isopropyl-7-methyl-2H,5H-pyrano[4,3-b]pyran-5-one (3a), also exhibited necrotic effects on the human IPC melanoma cells. (c) 2006 Elsevier Ltd. All rights reserved.

Lewis acids like BF 3 ·OEt 2 , TiCl 4 , ZnCl 2 ·OEt 2 , ZnI 2 , and InCl 3 in liquid SO 2 as a solvent at low temperatures have been found to be highly efficient in epoxyolefin cyclizations with pyrones as terminators.

Laccase initiated domino reactions of cyclohexane-1,3-diones with catechols using air as an oxidant afford 3,4-dihydro-7,8-dihydroxy-2H-dibenzofuran-1-ones with yields ranging from 70% to 97%.

Two new cyclic heptapeptides, integerrimides A and B, have been isolated from the latex of Jatropha integerrima. Their structures were elucidated by using extensive 1D and 2D NMR, MS, and chemical degradation. At 50 AM both peptides 1 and 2 significantly inhibited neurite outgrowth in neuronal cell culture. They also partially inhibited proliferation of human IPC-298 melanoma cells as well as migration of human Capan II pancreatic carcinoma cells, but were inactive in HSV-1, antifungal, and antimalarial assays.

Laccase-catalyzed domino reactions of 4-hydroxy-6-methyl-2H-pyran-2-one or substituted 4-hydroxy-2H-chromen-2-ones with catechols using molecular oxygen as an oxidant afford coumestans and related O-heterocycles with yields ranging from 51% to 99%.

Both natural and unnatural compounds with a 2H,5H-pyrano[4,3-b]pyran-5-one skeleton are of interest to medicinal chemistry as they exhibit several different biological activities. This heterocyclic ring systems is accessible by a Domino Knoevenagel coildensation/6pi-electron electrocyclization. A simple and rapid microwave assisted protocol of this Domino process has been developed for the preparation of libraries of substituted 2H,5H-pyrano[4,3-b]pyran-5-ones and related heterocyclic systems in a single preparative step by reaction of an alpha,beta-unsaturated aldehyde with a 6-substituted 4-hydroxy-2H-pyran-2-one.