Phosphorus-Containing Heterocyclic Compounds Derived from N-Vinylpyrroles

C-phosphorylation of N-vinylpyrroles with phosphorus(III) halides is shown to occur both at position 2 of the pyrrole ring and at the vinyl group. The properties of the resulting phosphorus-containing heterocyclic compounds and bis-phosphorylated N-vinylpyrroles are reported. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 495–499, 1997     

Chemical physics of cellulose nitration

The physical mechanisms responsible for the kinetics of nitration of cellulose raw materials of different origin have been studied. It has been shown that the main nitration rate-limiting factor is the speed of untwisting of supercoiled cellulose fibers. This process limits the penetration of nitrating agents into microcrystalline regions and, thus, the total reaction rate. The constructed physical model provides an adequate explanation of all the experimentally observed features of the cellulose nitration process, particularly as a function of cellulose origin (cotton, flax, wood) and preparation/treatment methods (sulfite, sulfate, bleached, refined with sulfurous or boric acids or acetone). The theoretical results have been tested in practice.     

From 4,5,6,7-tetrahydroindoles to 3- or 5-(4,5,6,7-tetrahydroindol-2-yl)isoxazoles in two steps: a regioselective switch between 3- and 5-isomers

(4,5,6,7-Tetrahydroindol-2-yl)alkynes, synthesized by cross-coupling of 4,5,6,7-tetrahydroindoles with aroyl(hetaroyl)bromoalkynes or ethyl bromopropynoate in the presence of K₂CO₃, regioselectively cyclize with hydroxylamine to either 3- or 5-(4,5,6,7-tetrahydroindol-2-yl)isoxazoles depending on the acidity of the reaction mixture: in the presence of acetic acid 3-isomers are formed (ca. 100% selectivity), while under neutral conditions the reaction is switched to 5-isomers (94–97% selectivity).     

Incomparably easy migration of functionalized enol substituent in pyrrole ring

Functionalized pyrroleьvь? enols, 2-(1-hydroxy-2.2-dicyanoethenyl)-1-methylpyrroles, at heating (75–135°C) unexpectedly readily rearranged in high yield into 3-isomers. Evidently the migration of the enol fragment involves a mesomeric zwitterion formed as a result of an intra- and intermolecular autoprotonation of the pyrrole ring by the acidic enol hydroxy group. Under similar conditions no migration of the ethenyl moiety occurred in 2-(1-hydroxy-2-carbamoyl-2-cyanoethenyl)-1-methylpyrroles. The quantum-chemical calculations (MP2/6-311G**) show a clear-cut distinction in the relative stability of 2- and 3-isomers of 1H- and 1-methylhydroxyethenylpyrroles: in the former case the 2-isomer is more stable, whereas in the 1-methyl-substituted compound, the 3-isomer.     

Unsaturated Phosphorus Compounds on the Basis of O-Vinyloximes

Russian Journal of General Chemistry -     

1,2-Dioximes in the trofimov reaction

3,3′-Dimethyl-1,1′-divinyl-2,2′-dipyrrole was obtained during the reaction of 3,4-hexanedione dioximes with acetylene under pressure in the potassium hydroxide-DMSO system. In the case of 1,2-cyclohexanedione dioxime 2,2′-dipyrrole and 2-pyridyl-and 2-acylpyrroles were isolated. α-Benzil and α-furil dioximes give 3,4-diphenyl-and 3,4-di(2-furyl)-1,2,5-oxadiazoles respectively in addition to their mono-and divinyl derivatives. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 39–46, January, 2006.     

Ethynylation of indoles with 1-benzoyl-2-bromoacetylene on Al2O3

Indoles are cross-coupled with 1-benzoyl-2-bromoacetylene on Al₂O₃ at room temperature under base and solvent-free conditions to afford 3-(2-benzoylethynyl)indoles in 22-76% yields, thus representing the first examples of direct ethynylation of the indole nucleus.