Kinetics and mechanism of formation of polymeric products during the hydroxyalkylation of parabanic acid with oxiranes

The kinetics of the reaction between N‐(2‐hydroxyalkyl) hydroparabanates (HAHP) and N,N′‐bis(2‐hydroxyalkyl) parabanates (HAP) with ethylene and propylene oxides were studied. The addition of oxiranes to imide function of HAHP led to the formation of HAP. Further reaction of HAP with oxiranes resulted in trioxoimidazolidine ring opening and polymeric products. The kinetics of the system was studied in detail. Based on the final kinetic equations, the mechanism of the reactions was postulated. The temperature dependences of kinetic parameters and analytical data provided experimental evidences supporting the mechanism. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 399–406, 2006     

A facile method for the synthesis of 1,3-oxathiolan-2-ones by reaction of oxiranes, sulfur, and carbon monoxide

A new method for the synthesis of 1,3-oxathiolan-2-ones has been developed. When oxiranes were allowed to react with sulfur in the presence of a catalytic amount of sodium hydride under pressurized carbon monoxide, the three-component coupling of oxiranes, sulfur, and carbon monoxide smoothly proceeded to give the 1,3-oxathiolan-2-ones in moderate to good yields. The reaction proceeded with a high regioselectivity and stereospecificity. For the reaction of oxiranes possessing an aromatic ring, the yields of the 1,3-oxathiolan-2-ones were lower than that of the oxiranes possessing no aromatic ring due to the formation of alkenes and thiiranes as byproducts. However, the product yields were improved by the addition of a catalytic amount of selenium.     

Regio- and Stereoselective Formation of 1,3-Oxathiolanes by Reactions of Thiocarbonyl Compounds with Oxiranes

Abstract

Lewis acid-catalyzed reactions of oxiranes with a variety of C═S compounds yield 1,3-oxathiolanes. The ring enlargement of monosubstituted oxiranes occurs regioselectively via cleavage of the O,C(3) bond of alkyl substituted oxiranes and the O,C(2) bond of phenyl oxirane. Furthermore, the reaction proceeds with inversion of the configuration at the center of the nucleophilic attack by the S-atom. The formation of thiocarbonylium ions as intermediates is supported by Wagner–Meerwein-type rearrangements. Enolized thioketones react with oxiranes to give enesulfanyl alcohols, which undergo an acid-catalyzed cyclization to yield 1,3-oxathiolanes.     

Formation of 1,2-dioxolanes using Mn(III)-based reaction of various arylacetylenes with 2,4-pentanedione and related reaction

The manganese(III)-based aerobic oxidation of arylacetylenes with 2,4-pentanedione at ambient temperature unexpectedly gave the 1,2-dioxolane derivatives in moderate yields together with a small amount of the oxiranes. The 1,2-dioxolanes underwent silica gel-assisted contraction to quantitatively give the oxiranes. The reaction pathway for the formation of the 1,2-dioxolanes and the by-product was discussed.     

On the reaction of α-(2-hydroxyphenoxy)alkylketones with dimethylsulphoxonium methylide. A novel route to 2-substituted-2,3-dihydro-2-hydroxymethyl-1,4-benzodioxins

A new route to 2-substituted-2,3-dihydro-2-hydroxymethyl-1,4-benzodioxins 3 based on the reaction of α-(2-hydroxyphenoxy)alkylketones 1 with dimethylsulphoxonium methylide in dimethylsulphoxide is reported. Besides the desired compounds 3 , the isomeric 2H-3,4-dihydro-1,5-benzodioxepines 4 were also isolated, generally as minor products. The concurrent formation of 3 and 4 has been interpreted as occurring through the intermediate oxiranes 2 , which can undergo intramolecular nucleophilic attack at either of the carbon atoms of the epoxy ring.     

Reaction of natural rubber latex with performic acid

Natural rubber in latex form was reacted with performic acid generated in situ. Due to high acidity of formic acid, the oxiranes formed were readily ring-opened to give hydroxyformate and glycol. In most cases, the latex coagulated within 2 hr of reaction and further reaction of the rubber coagulum resulted predominantly in the formation of tetrahydrofuran ring. Cross-linking is believed to occur via the formation of ether linkages. An i.r. technique for the analysis of the insoluble rubber is described. Quantitative analysis of the reaction products was made possible by using the methyl deformation band at 1380 cm^?1 as internal standard.     

Photoenolization-induced oxirane ring opening in 2,5-dimethylbenzoyl oxiranes to form pharmaceutically promising indanone derivatives

Irradiation of 2,5-dimethylbenzoyl oxiranes results in a relatively efficient and high-yielding formation of β-hydroxy functionalized indanones that structurally resemble biologically active pterosines. Nanosecond laser flash photolysis and quantum-chemical calculations based on density functional theory provided evidence that this photochemical transformation proceeds primarily via a photoenolization mechanism. Our study revealed considerable complexity of the mechanism and that structural modifications can significantly alter the reaction pathway and yield different products. The scope of this photochemical transformation for the synthesis of some pharmaceutically important compounds was investigated.     

Reaction of 2-silylmethylcyclopropyl ketones with in situ oxirane-derived aldehydes and formation of 2-hydroxymethyl tetrahydrofurans

The enolates formed from Lewis acid treatment of (2-trimethylsilylmethyl)cyclopropyl alkyl and aryl ketones reacted with aldehydes formed in situ from alkoxy-, aryl- and vinyl-substituted oxiranes to generate aldol products in good yields. Selected aldol products were conveniently transformed into highly substituted tetrahydrofurans under oxidative conditions.     

Stereospecific cycloaddition of heterocumulenes to oxiranes catalyzed by organotin halide complexes

Stereospecific cycloaddition of 2,3-disubstituted oxiranes to heterocumulenes, including carbodiimides, isocyanates and carbon dioxide, is catalytically promoted by dialkyltin diiodide-hexamethylphosphoric triamide (HMPA) system, producing various five-membered heterocycles, where the configuration of the carbons in the oxirane ring is retained. In particular, the addition of isocyanates to oxiranes gave stereo-specifically two types of products, dioxolan-2-imines and oxazolidin-2-ones independently, while the rearrangement of the former to the latter product has been already proposed.     

Unusual cycloaddition of oxiranes with isocyanates catalyzed by tetraphenylstibonium iodide; selective formation of 3,4-disubstituted oxazolidinones.

Tetraphenylstibonium iodide is a general and versatile catalyst for the selective formation of unusual cycloadducts, 3,4-disubstituted oxazolidinones, in the reaction of oxiranes with isocyanates.     

非对称环氧乙烷的区域选择性亲核开环反应

本文总结了常用亲核试剂对非对称环氧乙烷的亲核开环反应及其区域选择性。强亲核性的亲核试剂通常只受空间效应影响,进攻非对称环氧乙烷位阻小的碳原子,对于烯基取代环氧乙烷还可以进攻烯基的β-碳原子发生S_N2'开环反应,其他亲核试剂同时受空间效应和电子效应的影响,对于烷基环氧乙烷通常进攻其取代少的碳原子, 空间效应起主导作用,而对芳基和烯基取代环氧乙烷开环反应通常发生在环氧乙烷芳甲位和烯丙位的碳原子上, 电子效应起主导作用。在质子酸或强Lewis酸存在下,虽然单烷基环氧乙烷的开环仍然发生在其取代少的碳原子上,但对于芳基、烯基和同碳双取代环氧乙烷,亲核开环反应将主要受电子效应控制,一般亲核试剂倾向于进攻环氧乙烷的芳甲位、烯丙位或多取代的碳原子。分子内的亲核开环反应主要受成环时环大小的控制, 成环时的倾向是五元环> 六元环> 七元环。环氧乙烷亲核开环的区域选择性是环氧乙烷和亲核试剂空间效应和电子效应平衡的结果。     

Réactions de germylènes avec divers oxirannes et le thiiranne. Mise en évidence de germanones et germathiones intermédiaires. Communication préliminaire

Complexed dialkylgermylenes R₂GeNR₃ or R₂GePy react with oxiranes or thiirane and lead to dialkylgermanone and germathione via germaoxetanes or germathiacyclobutane. The formation of germadioxolanes or germadithiolane finally observed arises from condensation of dialkylgermanone (or germathione) on oxiranes (or thiirane).     

Differentiation of keto groups in the Michael adducts of levoglucosenone with cyclohexanone

The keto group in the carbohydrate residue of diastereoisomeric Michael adducts of levoglucosenone and cyclohexanone is more reactive than that in the cyclohexanone fragment. The adducts have been converted to the corresponding ethylene, trimethylene, and dimethyl ketals, tosylhydrazones, oxiranes, and Wittig methylenation products with complete or high regioselectivity.     

氧化铝催化下环氧烷与芳胺的反应——β-氨基醇的合成

在氧化铝催化下, 以芳氧甲基环氧烷和芳胺为原料, 合成了一系列1-芳氧基-3-芳氨基异丙醇衍生物. 产物结构均由IR, MS和¹H NMR进行表征.     

Bis(oxiranes) Containing Cyclooctane Core: Synthesis and Reactivity towards NaN3

Reactions of oxirane ring opening provide a powerful tool for regio- and stereoselective synthesis of polyfunctional and heterocyclic compounds, widely used in organic chemistry and drug design. Cyclooctane, alongside other medium-sized rings, is of interest as a novel molecular platform for the construction of target-oriented leads. Additionally, cyclooctane derivatives are well known to be prone to transannular reactions, which makes them a promising object in the search for novel approaches to polycyclic structures. In the present work, a series of cyclooctanediones was studied in Corey-Chaykovsky reactions, and novel spirocyclic bis(oxiranes) containing cyclooctane core, namely, 1,5-dioxadispiro[2.0.2.6]dodecane and 1,8-dioxadispiro[2.3.2.3]dodecane, were synthesized. Ring opening of the obtained bis(oxiranes) upon treatment with sodium azide was investigated, and it was found that the reaction path is determined by the reciprocal orientation of oxygen atoms in the oxirane moieties. Diastereomers of the bis(oxiranes) with cis-orientation underwent independent ring opening, supplying corresponding diazidodiols, while in the case of stereoisomers with trans-orientation, domino-like reactions occurred, including intramolecular nucleophilic attack and the formation of a novel three- or six-membered O-containing ring. Summarily, a straightforward approach to polyfunctional compounds containing cyclooctane or oxabicyclo[3.3.1]nonane cores, employing bis(oxiranes), was elaborated.     

2-氯甲基苯并恶唑的Darzens反应研究

本文报道用2-氯甲基苯并恶唑作为卤代物,进行Darzens反应。义固体氧化钾作碱,在非质子极性溶剂N,N-甲基酰胺中,将其与相应的羰基化合物反应, 生成了环氧化合物。     

Heterogeneous asymmetric ring-opening reactions of prochiral epoxides included as guest molecules in tri-o-thymotide clathrates.

Enantiomorphous tri-o-thymotide clathrates of prochiral oxiranes were submitted to the action of gaseous hydrogen halides. Ring-opening reactions ensued that differ from those reported in homogeneous phase, showing a considerable modification of the chemical reactivity of the external reagent in the host lattice. Chirality transfer from the host receptors to the guest products was also observed, but with a poor efficiency.     

Synthesis of some sulfonium salts and ylides containing the isoxazole nucleus

Some dimethylisoxazolylmethylsulfonium salts and the corresponding ylides were synthetized and their chemical behaviour studied. Dimethylsullonium-5-isoxazolyl methylides (XIa,b) give 5-isoxazolyloxiranes (XIIa,d) and XIII when allowed to react with carbonyl compounds. Ring opening products from these oxiranes are also reported.     

Synthesis of aryloxyacetaldehydes and <Emphasis Type="Italic">N</Emphasis>-(aryloxyethyl)cyclohexanamine hydrochloroides

Oxidation of 2-(aryloxymethyl)oxiranes with periodic acid gave a series of aryloxyacetaldehydes which reacted with cyclohexylamine in THF, and subsequent reduction of Schiff bases thus obtained with sodium tetrahydridoborate resulted in the formation of the corresponding secondary amines which were isolated and characterized as hydrochlorides.     

On the reactivity of ascomycin at the binding domain. Part 3: Reactivity of the binding domain towards diazomethane

A thorough product analysis of the reaction of ascomycin with diazomethane has been performed. Apart from the expected oxiranes (epimeric at C9), a whole range of novel derivatives bearing various modifications in the binding domain were obtained. Proposed mechanisms for their formation and stereochemical aspects are discussed.