The conversion of furans into phosphinines

The [4+2] cycloadducts between furan compounds and a methylenechlorophosphane pentacarbonyltungsten complex are converted into the corresponding 2-hydroxy- or 2-bromophosphinine complexes by treatment with BBr(3) and triethylamine. The X-ray crystal structure of the parent 2-phosphaphenol complex shows that the hydroxy substituent is coplanar with the ring and that the conjugation between the π lone pair of electrons on the oxygen atom and the ring leads to lengthening of the P-C(OH) bond. This complex is methylated at the phosphorus atom by methyl iodide with disruption of the ring aromaticity. The complex is further silylated, acylated, and triflated at the oxygen atom with retention of the aromatic structure, and decomplexation by 1,2-bis(diphenylphosphino)propane (DPPE) leads to the free parent 2-phosphaphenol. The comparison of the X-ray crystallographic structural analysis of the 2-bromophosphinine complex with an earlier structure of the analogous 2-chlorophosphinine complex suggests that 2-bromo species is a better ligand than 2-chlorophosphinine. When the [4+2] adducts are treated with BBr(3) and water, a 2-hydroxy-3-bromo-1,2,3,6-tetrahydrophosphinine derivative is obtained, which yields a seven-membered 2,1-phosphaoxepin when treated with an amine.     

Thermal conversion of 2-methylphenylazo-compounds to diareno-1,2-diazepines

Examples are given of the synthesis of bis-annulated 1,2-diazepines $\text{via}$ thermal intramolecular condensation of 2-methylphenylazo-arenes and -heteroarenes carrying an $\text{ortho}$′ nucleofugal group.     

Gold-catalyzed consecutive [1,2] alkyl migration-oxygen transfer reaction of 2-alkynyl-1-tetralones

Gold-catalyzed isomerization of 2-alkynyl-1-tetralones afforded the corresponding 2-naphthylmethyl ketones in good to high yields. For example, the reaction of 2-{4-(methoxyphenyl)methyl}-2-(phenylethynyl)-3,4-dihydronaphthalen-1(2H)-one and 2-benzyl-2-(phenylethynyl)-3,4-dihydronaphthalen-1(2H)-one in the presence of 5 mol % of (Ph₃P)AuCl and 5 mol % of AgOTf in THF at 50 °C gave 2-{1-(4-methoxyphenylmethyl)naphthalen-2-yl}-1-(4-methoxyphenyl)ethanone and 2-(1-benzylnaphthalen-2-yl)-1-phenylethanone in 85% and 96% yields, respectively. The present reaction proceeds through [1,2] alkyl migration followed by oxygen transfer.     

Synthesis of 1-alkynyl-2-dialkylaminocyclopropanes and 1-alkynyl-2-diazolylcyclopropanes by reactions of 1-alkynyl-1-chlorocyclopropanes with amines and their lithium derivatives

Reactions of 1-alkynyl-1-chlorocyclopropanes with lithium dialkylamides gave previously unknown 1-alkynyl-2-dialkylaminocyclopropanes. 1-(Alk-1-ynyl)-2-diazolylcyclopropanes were obtained by reactions of 1-alkynyl-1-chlorocyclopropanes with diazoles in the presence of KOH in DMSO at 100 °C. These reactions passed through the formation of conjugated alky-nylcyclopropenes and reversible addition of amide anions to them. The regioselectivity and stereoselectivity of these transformations depend on the substituents in the starting chlorocyclopropanes and amines.     

Sonogashira cross-coupling of 3-bromo-1,2-diones: an access to 3-alkynyl-1,2-diones

A new general method for the synthesis of enols of cyclic 3-alkynyl-substituted 1,2-diketones is developed. Sonogashira cross-coupling of silyl enolates of cyclic 3-bromo-cyclopentane- and 3-bromo-cyclohexane-1,2-diones with variety of substituted acetylenes afforded enols of cyclic 3-alkynyl-1,2-diones with good yields (up to 93%) in a short reaction time. The starting 3-bromo-1,2-diones are easily obtainable by direct bromination of 1,2-diones with NBS.     

A facile synthesis of 1,2-oxaphospholenes and stereoselective conversion into oxaphospholanes

Treatment of α-acylallylphosphonates with m-CPBA in the presence of MgSO₄, afforded 1,2-oxaphosphol-3-enes 2-oxides and the subsequent cuprate addition produced 1,2-oxaphospholanes stereoselectively.     

Palladium-catalyzed cyclization of 1-alkynyl-8-iodonaphthalene and double isocyanides for the synthesis of acenaphtho[1,2-b]pyrroles

A palladium-catalyzed formal [2 + 2 + 1] cyclization of 1-alkynyl-8-iodonaphthalene with double isocyanides is developed herein. The transformation worked well to produce a series of 7H-acenaphtho[1,2-b]pyrrole with a broad reaction scope. Isocyanides play a dual role in the reaction. One is a C1 building block, and another is used as C1N1 component. In the process, the [2 + 2 + 1] cyclization involves imidoylation, regioselective addition of imidoylpalladium species into alkyne, double imidoylation, and another addition of the resulting imidoylpalladium species into imine bonds.     

A new heterocyclic rearrangement: conversion of 2-vinylpyrazolium salts into 1,2-dihydropyrimidines

Treatment of 2-vinylpyrazolium salt $\text{1}$ in basic medium yields the 1,2-dihydropyrimidine $\text{2}$. The structure of $\text{2}$ was established by analytical and spectroscopic methods.     

Thermal catalytic conversion of the used isobutyl isoprene rubber into valuable hydrocarbons

An environment friendly method, thermal catalytic pyrolysis of used isobutyl isoprene rubber was investigated. In this method, the used inner butyl tube rubbers were catalytically pyrolyzed into valuable hydrocarbons and carbon black. In this method, the tube rubber was pyrolyzed both thermally (with out catalyst) and catalytically in a batch reactor under atmospheric pressure. The effect of temperature, the amount of catalyst, and the reaction time on the yields of the pyrolyzed products were investigated. Char yield decreased with increase of pyrolysis temperature while total gas and liquid yields increased. The liquid fraction was obtained with boiling point up to 478 K. At optimum conditions, the liquid product was collected and analyzed for different fuel properties. Typical analysis of the used isobutyl isoprene rubber oil for both the cases of parent and refluxed oil has been performed. Phenols and carbonyls were quantitatively determined by spectrophotometric methods using folin-denis and phenyl hydrazine reagents, respectively. The distillation data showed that ~100% of oil has boiling point <473 K which is the boiling point for 80% of distilled product in commercial kerosene. Its specific gravity, viscosity, freezing point, Cetane number, and diesel index were also within the limits of kerosene.     

Preparation of tritylated 1,2-0-(1-methoxycarbonyl)ethylidene derivatives of carbohydrates and their conversion into tritylated 1,2-0-(1-cyano)ethylidene derivatives

Conclusion Tritylation of 1,2-0-1-(methoxycarbonyl)ethylidene derivative of carbohydrates followed by ammonolysis of the methoxycarbonyl group and dehydration was proposed as an alternative method for the preparation of tritylated 1,2-0-1-(cyano)ethylidene derivatives for use as monomers for polycondensation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1126–1131, May, 1987.     

4-Diazomethylcoumarins and related stable heteroaryldiazomethanes. Thermal conversion into condensed pyrazoles

4-Diazomethyl-substituted coumarins, 1-methyl-2(1H)-quinolinones, 1 -thiocoumarin and their tricyclic analogs were found to be easily cyclized into the corresponding pyrazole isomers condensed with heteroaromatics. Thermodependent feature of these conversions and the remarkably accelerating effect of the alkyl substituent peri to the diazomethyl group were realized. Some other diazomethyl compounds connected with 2-pyridinone, 3-pyrazolone, chromone and 1-thiochromone were prepared, and their stability and thermal properties were compared.     

Thermal decomposition of 1,2 butadiene

The thermal decomposition of 1,2 butadiene has been studied behind reflected shock waves over the temperature and total pressure ranges of 1300–2000 K and 0.20–0.55 atm using mixtures of 3% and 4.3% 1,2 butadiene in Ne. The major products of the pyrolysis are C₂H₂, C₄H₂, C₂H₄, CH₄ and C₆H₆. Toluene was observed as a minor product in a narrow temperature range of 1500–1700 K. In order to model successfully the product profiles which were obtained by time-of-flight mass spectrometry, it was necessary to include the isomerization reaction of 1,2 to 1,3 butadiene. A reaction mechanism consisting of 74 reaction steps and 28 species was formulated to model the time and temperature dependence of major products obtained during the course of decomposition. The importance of C₃H₃ in the formation of benzene is demonstrated.     

Usual conversion of phenylthioacetylene into 1,2-di(phenylthio)-ethene in the KOH-DMSO-cyclohexanone oxime system

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, p. 1702, July, 1989.     

Borane-induced radical reduction of 1-alkenyl- and 1-alkynyl-λ-iodanes with tetrahydrofuran

Exposure of 1-alkenyl(phenyl)- and 1-alkynyl(phenyl)-λ³-iodanes to THF at room temperature in the presence of a catalytic amount of trialkylborane results in smooth reduction to give 1-iodo-1-alkenes and 1-iodo-1-alkynes as major products, respectively. The key step in the reductions probably involves a single-electron transfer from α-tetrahydrofuryl radical to the λ³-iodanes, which generates the labile [9-I-2] iodanyl radicals.     

Studies on the generation of unnatural C-nucleosides with 1-alkynyl-2-deoxy-D-riboses

1-alkynyl-2-deoxy-D-riboses 7 and 8 were independently synthesized and subsequently used to generate several novel C-nucleosides.     

Recent developments in the chemistry of donor-functionalized phosphinines

This review provides an overview of the most significant strategies developed in recent years for the preparation of donor-functionalized phosphinines and new developments in this field are highlighted. Selected synthetic procedures for the introduction of additional sulfur-, oxygen-, phosphorus-, and nitrogen-donor groups into the heterocyclic framework are presented. Examples of their coordination chemistry and potential applications in homogeneous catalysis and phosphorus containing molecular materials will be given.     

One-pot conversion of glycals to cis-1,2-isopropylidene-alpha-glycosides

Described is a general method for the conversion of glycals to the corresponding 1,2-cis-isopropylidene-alpha-glycosides. Epoxidation of glycals with dimethyldioxirane followed by ZnCl(2)-catalyzed addition of acetone converted a variety of protected glycals into 1,2-cis-isopropylidene-alpha-glycosides in good yield. The reaction is compatible with a range of protecting groups, including esters, benzyl ethers, and silyl ethers, as well as free hydroxyl groups. This method has been applied to develop a synthesis of protected glucuronic acid 1, a key intermediate in the synthesis of glycosaminoglycans. Compound 1 was produced in seven steps and 32% overall yield.     

Facile addition of alkynes to aza-aromatic systems: a new protocol for the preparation of 2-alkynyl-1,2-dihydroquinolines

1-Alkynes undergo smooth addition to activated quinolines, isoquinolines and pyridines in the presence of copper iodide/ⁱPr₂NEt under extremely mild conditions to afford 2-alkynyl-1,2-dihydroquinolines in excellent yields with high selectivity. This method is also useful for functionalization of monocyclic pyridines.     

Synthesis of phosphinines and phosphinanes using zirconium chemistry

Ring expansion of readily available zirconacyclopentadienes or zirconacyclopentanes by insertion of chloro(trimethylsilyl)methyllithium followed by metathesis with phosphorous trichloride provides a novel route to λ³-phosphinines (phosphabenzenes) or phosphinanes.