Reaction Of Nitrile Oxides Research Articles

3 + 2] Cycloaddition of nitrile oxides to dichloropropenes and 1,3‐dichlorobut‐2‐ene: A regioselectivity issue

AbstractThe reaction of nitrile oxides with 2,3‐dichloroprop‐1‐ene, 1,3‐dichloroprop‐1‐ene, and 1,3‐dichlorobut‐2‐ene leads to 5‐(chloromethyl)isoxazoles, 4‐(chloromethyl)isoxazoles, or to mixtures of both regioisomers. The direction of cycloaddition and reactivity of substrate is determined by the steric hindrance at the terminal carbon atom of the alkene double bond. It has been found that the isomeric products of cycloaddition of nitrile oxides to 1,3‐dichloropropene have significantly different dehydrochlorination capabilities. The experimental data on the regioselectivity of cycloaddition and the relative reactivity of substrates are in agreement with the results of quantum chemical calculations.

A metal-free approach for in situ regioselective synthesis of isoxazoles via 1,3 dipolar cycloaddition reaction of nitrile oxide with propargyl bromide

A metal-free approach for in situ regioselective synthesis of isoxazoles via 1,3 dipolar cycloaddition reaction of nitrile oxide with propargyl bromide

1,3-Dipolar cycloaddition reactions of acyl phosphonates with nitrile oxides: synthesis of phosphonate-containing dioxazole derivatives

New phosphonate-containing five-membered heterocyclic dioxazole derivatives are synthesized via 1,3-dipolar cycloaddition reactions of nitrile oxides used as dipole with acyl phosphonates under basic conditions. Herein, acyl phosphonates take part in the cyclization process as a dipolarophile to afford the related dioxazole compounds in moderate-to-good yields (49–84%). Substituted aryl nitrile oxides and aroyl phosphonates were employed in the 1,3-dipolar cycloaddition reactions where triethylamine was the effective tertiary base. Alkyl version of acyl phosphonate also afforded the expected cycloadduct, that is, dimethyl 5-isopropyl-3-phenyl-1,4,2-dioxazol-5-yl-5-phosphonate. Diethyl/dimethyl 3,5-aryl-1,4,2-dioxazol-5-yl-5-phosphonate derivatives are fully characterized by using 1H NMR, 13C NMR, 31P-NMR, and FT along with high-resolution mass spectroscopy.

Postsynthetic Modification of Metal-Organic Frameworks through Nitrile Oxide-Alkyne Cycloaddition.

Postsynthetic modification of metal-organic frameworks is an important method to tailor their properties. We report on the nitrile oxide-alkyne cycloaddition (NOAC) as a modification tool, a reaction requiring neither strained alkynes nor a catalyst. This is demonstrated with the reaction of nitrile oxides with PEPEP-PIZOF-15 and -19 at room temperature. PIZOF-15 and -19 are porous Zr-based MOFs (BET surface areas 1740 and 960 m2 g-1, respectively) consisting of two mutually interpenetrating UiO-type frameworks with linkers of the type -O2C[PE-P(R1,R2)-EP]CO2- (P, phenylene; E, ethynylene; R1 and R2, side chains at the central benzene ring with R1 = R2 = OCH2C≡CH or R1 = OCH2C≡CH and R2 = O(CH2CH2O)3Me). Their syntheses, using benzoic acid as a modulator, and their characterization are reported herein. The propargyloxy (OCH2C≡CH) side chains contain the ethyne moieties needed for NOAC. Formation of nitrile oxides through oxidation of oximes in aqueous ethanolic solution in the presence of PEPEP-PIZOF-15 and -19 resulted in the reaction of 96-100% of the ethyne moieties to give isoxazoles. Thereby the framework was preserved. The type of nitrile oxide RCNO was greatly varied with R being isopentyl, tolyl, 2-pyridyl, and pentafluorophenyl. A detailed NMR spectroscopic investigation showed the formation of the 3,5-disubstituted isoxazole to be clearly favored (≥96%) over that of the constitutional isomeric 3,4-disubstituted isoxazole, except for one example.

A theoretical investigation on the regioselectivity of the [3+2] cycloaddition of nitrile oxide and N-vinylpyrrole

Theoretical calculations were performed on the [3+2] cycloaddition (32CA) reaction of nitrile oxide and N-vinylpyrrole. The regiochemistry of the reaction has been studied based on potential energy surface analysis and global and local reactivity indices of the reactants. The global electron density transfer (GEDT) calculations at the possible transition states revealed that this cycloaddition has a nearly non-polar character. The ELF topological analyses of the selected structures involved in the intrinsic reaction coordinate (IRC) of TS1a suggests that this 32CA reaction takes place through a two-stage one-step mechanism.

Prediction of the regioselectivity of 1,3-dipolar cycloaddition reactions of nitrile oxides with 2(5H)-furanones using recent theoretical reactivity indices

Prediction of the regioselectivity of 1,3-dipolar cycloaddition reactions of nitrile oxides with 2(5H)-furanones using recent theoretical reactivity indices

A DFT study of the mechanism and the regioselectivity of [3 + 2] cycloaddition reactions of nitrile oxides with α,β-acetylenic aldehyde

ABSTRACTA DFT study of the (32CA) reaction of a series of some nitrile oxides with electron-deficient alkyne (3-phenylpropionlaldehyde) in gas phase and in toluene has been carried out using B3LYP functional with 6-31G(d) basis set. Two reactive channels 4- and 5-associated with the two regioisomeric modes have been located and characterised. These 32CA reactions are characterised by a low asynchronous one-step mechanism with a low-polar character. Analysis of the DFT reactivity indices indicates that the nucleophilic centre of the different nitrile oxides accounts for the 4-regioselectivity. Our calculations are in a good agreement with the experimental findings.

ChemInform Abstract: Recent Advances in Isoxazole Chemistry

AbstractReview: 460 refs.

Correction: Application of chiral ligands: carbohydrates, nucleoside-lanthanides and other Lewis acid complexes to control regio- and stereoselectivity of the dipolar cycloaddition reactions of nitrile oxides and esters

Correction for ‘Application of chiral ligands: carbohydrates, nucleoside-lanthanides and other Lewis acid complexes to control regio- and stereoselectivity of the dipolar cycloaddition reactions of nitrile oxides and esters’ by Mirosław Gucma et al., RSC Adv., 2015, 5, 13112–13124.

ChemInform Abstract: Reaction of Nitrile Oxides with Masked o‐Benzoquinones; Synthesis of Highly Functionalized Isoxazolines.

AbstractThe reaction of the masked o‐benzoquinones with nitrile oxides, generated in situ from hydraxamoyl chlorides provides the expected [3 + 2]‐cycloaddition isoxazoline products of the type (V) or the rearranged isoxazolines of the type (III).

Reaction of Nitrile Oxides with Masked o‐Benzoquinones; Synthesis of Highly Functionalized Isoxazolines

AbstractMasked o‐benzoquinones, on reaction with nitrile oxides generated in situ from the corresponding hydroxamoyl chlorides, provide [3+2] cycloaddition products or novel isoxazoline derivatives through an unprecedented rearrangement. The isolated [3+2] cycloadducts could be transformed into the corresponding isoxazoline derivatives in the presence of Et3N and highly functionalized benzisoxazoles in the presence of 4 N HCl.

KF/Al2O3: Solid-Supported Reagent Used in 1,3-Dipolar Cycloaddition Reaction of Nitrile Oxide

The stereoselective synthesis of 2-isoxazolidine through 1,3-dipolar cycloaddition reaction of nitrile oxide, which is in situ generation from aldoxime in the presence of N-bromosuccinamide and solid-supported reagent KF/Al2O3 at room temperature, is reported. KF/Al2O3 is sufficiently basic such that it can replace organic bases such as Et3N used in typical procedures and it catalyses the reaction to enhance the rate of the reaction.

ChemInform Abstract: Synthesis of [1,2,4]Oxadiazolo[4,5‐a]thiazolo[2,3‐b]pyrimidin‐9(10H)‐ones via 1,3‐Dipolar Cycloaddition of Nitrile Oxide to Thiazolo[3,2‐a]pyrimidin‐3‐one Derivatives.

A new class of [1,2,4]oxadiazolo[4,5-a]thiazolo[2,3-b]pyrimidin-9(10H)-one was prepared in moderate yields by the reaction of nitrile oxide with 2-arylmethylidene-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidin-3-one. The reaction site of dipolarphile is the CN of thiazolo[3,2-a]pyrimidin-3-one rather than the expected CC of arylmethylidene. The structures of the products were characterized thoroughly by IR, elemental analysis, MS, and NMR analysis.

ChemInform Abstract: Reaction of Nitrile Oxides with Nitrogen Oxides. Part 1. Reaction with Dinitrogen Tetroxide.

ChemInform 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.

ChemInform Abstract: Reaction of Nitrile Oxides with Nitrogen Oxides. Part 2. Reaction with Nitrogen Oxide and Dinitrogen Trioxide.

ChemInform 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.

ChemInform Abstract: 1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides and Nitrile Imines with 2-Methoxyvinyl Phenyl Ketone.

Nitrile oxides react regioselectively with 2-methoxyvinyl phenyl ketone 1 to give 4-benzoylisoxazoles 4 via elimination of methanol from the primary cycloadducts 3. After heating with an excess of nitrile oxide bis-cycloadducts 5 were also formed. Reactions of nitrile imines with 1 are less regioselective yielding both 4-benzoylpyrazoles 9 and 5-benzoytpyrazoles 10, whereas no bis-cycloadducts were isolated.

ChemInform Abstract: Synthesis and Antiviral Activity of 5-Heteroaryl-Substituted 2′- Deoxyuridines.

The synthesis of 5-heteroaryl-substituted 2'-deoxyuridines is described. The heteroaromatics were obtained from three different 5-substituted 2'-deoxyuridines. Cycloaddition reaction of nitrile oxides on the 5-ethynyl derivative 1 gave the isoxazoles 4a-e. The thiazole derivatives 14a-c were obtained from the 5-thiocarboxamide 11, while 5-pyrrol-1-yl-2'-deoxyuridine (17) could be synthesized directly from 5-amino-2'-deoxyuridine. The compounds were evaluated for antiviral activity. Selective activity against herpes simplex virus type 1 (HSV-1) and varicella zoster virus (VZV) was noted for 5-(3-bromoisoxazol-5-yl)-2'-deoxyuridine (4c). The compound was inactive against herpes simplex virus type 2, cytomegalovirus, and thymidine kinase (TK)-deficient mutants of HSV-1 and VZV, which indicates that, most likely, its antiviral activity depends on phosphorylation by the virus-specified TK.

ChemInform Abstract: Spiroheterocycles from Reaction of Nitrile Oxides with Heterocyclic o- Quinodimethanes.

Abstract 1,3-Dipolar cycloaddition to o -quinodimethanes has been observed for the first time in the reaction of pyrazole and isoxazole o -quinodimethanes 4–6 with the stable nitrile oxides 7 and 8. The products, dispiroisoxazolines 9–14 , were isolated in moderate yields. In all cases the “anti” addition stereoisomers 9a–14a were formed, as was established by X-ray crystallographic analysis on 13a and 14a , whereas the “syn” addition stereoisomers were isolated only in the case of 11b and 13b . When the bromosubstituted o -quinodimethane 16 was employed the monosphiroisoxazolines 17 and 18 were obtained.

ChemInform Abstract: Metal Ion Mediated Diastereoface-Selective 1,3-Dipolar Cycloaddition of Nitrile Oxides with Dipolarophiles Bearing an Oxazolidinone Chiral Auxiliary.

Abstract Magnesium ion-mediated cycloaddition reactions of nitrile oxides to chiral 3-acryloyl-2-oxazolidinones lead to highly diastereoselective formation of 2-isoxazolines. The magnesium ion serves to fix the α,β-unsaturated moiety through chelation to effect chiral shielding. These asymmetric reactions provide the first successful examples of Lewis acid-mediated stereocontrol of nitrile oxide cycloaddition reactions to electron-deficient dipolarophiles.

Synthesis of [1,2,4]Oxadiazolo[4,5‐a]thiazolo[2,3‐b]pyrimidin‐9(10H)‐ones via 1,3‐Dipolar Cycloaddition of Nitrile Oxide to Thiazolo[3,2‐a]pyrimidin‐3‐one Derivatives

AbstractA new class of [1,2,4]oxadiazolo[4,5‐a]thiazolo[2,3‐b]pyrimidin‐9(10H)‐one was prepared in moderate yields by the reaction of nitrile oxide with 2‐arylmethylidene‐6,7‐dihydro‐5H‐thiazolo[3,2‐a]pyrimidin‐3‐one. The reaction site of dipolarphile is the CN of thiazolo[3,2‐a]pyrimidin‐3‐one rather than the expected CC of arylmethylidene. The structures of the products were characterized thoroughly by IR, elemental analysis, MS, and NMR analysis.