1017-09-0Relevant articles and documents
Regioselectivity of 1,3-Dipolar Cycloadditions of Benzonitrile Oxide to Alkenyl Boronic Esters: An Experimental and Computational Study
Jeong, Jo,Zong, Kyukwan,Choe, Joong Chul
, p. 1007 - 1014 (2017)
1,3-Dipolar cycloaddition reactions of benzonitrile oxide to monosubstituted or 1,1-disubstituted alkenyl boronic ester gave only 2-isoxazolines, bearing the boronic ester group at the 5-position of the ring. On the other hand, the cycloaddition reactions of benzonitrile oxide with trans-1,2-disubstituted alkenyl boronic esters produced 2-isoxazolines, bearing the boronic ester group at the 4-position of the ring. We used quantum mechanical calculations to investigate two regioisomeric channels that were associated with the formation of 2-isoxazolines, bearing the boronic ester group at the 4-position or 5-position. The study revealed that the experimental results agreed well with the parameters based on the transition state energies in gas or solvent phase. The study also informed that all the cycloaddition reactions proceed in a spontaneous and exergonic fashion.
A facile method for the preparation of 4-hydroxy-Δ2-isoxazolines via a cycloaddition/oxidation procedure employing nitrile oxides and vinylboronic esters
Wallace, Richard H.,Liu, Jinchu
, p. 7493 - 7496 (1994)
The 1,3-dipolar cycloaddition of aromatic nitrile oxides with trans-1,2-disubstituted vinylboronic esters affords the 4-boronic ester substituted Δ2-isoxazoline as the major regioisomer. If the reaction mixture is treated with t-BuOOH the corre
Asymmetric Hydrogenation of Isoxazolium Triflates with a Chiral Iridium Catalyst
Ikeda, Ryuhei,Kuwano, Ryoichi
supporting information, p. 8610 - 8618 (2016/07/07)
The iridium catalyst [IrCl(cod)]2–phosphine–I2(cod=1,5-cyclooctadiene) selectively reduced isoxazolium triflates to isoxazolines or isoxazolidines in the presence of H2. The iridium-catalyzed hydrogenation proceeded in high-to-good enantioselectivity when an optically active phosphine–oxazoline ligand was used. The 3-substituted 5-arylisoxazolium salts were transformed into 4-isoxazolines with up to 95:5 enantiomeric ratio (e.r.). Chiral cis-isoxazolidines were obtained in up to 89:11 e.r., with no formation of their trans isomers, when the substrates had a primary alkyl substituent at the 5-position. The mechanistic studies indicate that the hydridoiridium(III) species prefers to deliver its hydride to the C5 atom of the isoxazole ring. The hydride attack leads to the formation of the chiral isoxazolidine via a 3-isoxazoline intermediate. Meanwhile, in the selective formation of 4-isoxazolines, hydride attack at the C5 atom may be obstructed by steric hindrance from the 5-aryl substituent.
One-pot synthesis of isoxazolines from aldehydes catalyzed by iodobenzene
Han, Liuquan,Zhang, Bijun,Xiang, Changbin,Yan, Jie
, p. 503 - 509 (2014/03/21)
A convenient one-pot, three-step procedure for the synthesis of isoxazolines starting from aldehydes has been developed involving catalytic cycloaddition between nitrile oxides and alkenes, in which iodobenzene is used as the catalyst for the in situ generation of a hypervalent iodine intermediate. In this approach, the aldehydes are first transformed with hydroxylamine sulfate into aldoximes, which are then oxidized to nitrile oxides by the in situ generated hypervalent iodine intermediate; finally, a 1,3-dipolar cycloaddition between the nitrile oxides and alkenes occurs to provide the isoxazolines in moderate to good yields.
An environmentally benign synthesis of isoxazolines and isoxazoles mediated by potassium chloride in water
Han, Liuquan,Zhang, Bijun,Zhu, Min,Yan, Jie
supporting information, p. 2308 - 2311 (2014/04/17)
An effective and environmentally benign procedure for the synthesis of isoxazolines and isoxazoles has been developed by a cycloaddition of nitrile oxides with alkenes or alkynes in water. In this approach, potassium chloride is first oxidized into chlorine in water by the environmentally friendly oxidant Oxone, then aldoximes are oxidized into nitrile oxides by the in situ generated hypochlorous acid, finally a 1,3-dipolar cycloaddition between nitrile oxides and alkenes or alkynes occurs to provide the corresponding isoxazolines and isoxazoles in good yields.
Hypervalent iodine-catalyzed cycloaddition of nitrile oxides to alkenes
Xiang, Changbin,Li, Tingting,Yan, Jie
, p. 682 - 688 (2014/01/17)
A new and convenient method for preparation of isoxazolines was developed by a catalytic cycloaddition of nitrile oxides generated in situ from aldoximes to alkenes in the presence of a catalytic amount of iodobenzene. In this protocol, iodobenzene was fi
Flash vacuum pyrolysis of 1,2,5-oxadiazole 2-oxides and 1,2,3-triazole 1-oxides
Mitchell, William R.,Paton, R. Michael
experimental part, p. 34 - 54 (2011/02/21)
The flash vacuum pyrolysis (FVP, 450-600 °C/10-3 mmHg) of 3,4-diaryl- and 3,4-dialkyl-1,2,5-oxadiazole 2-oxides (furoxans) has been investigated. In all cases the 1,2,5-oxadiazole ring cleaved cleanly at O(1)-N(2) and C(3)-C(4) to afford two nitrile oxide fragments, which were trapped in high yield (75-97%) as their isoxazoline cycloadducts by reaction with alk-1-enes. At higher temperatures (700-800 °C) isocyanates were formed as by-products. The dimerisation of acetonitrile oxide to dimethylfuroxan was followed by 1H NMR spectroscopy, and the rate constant for the 2 nd order reaction determined. The furoxans were converted into isocyanates in good yield (61-95%) by FVP, followed by sulfur dioxide-mediated isomerisation of the resulting nitrile oxides. 2,4,5-Trisubstituted-1,2,3- triazole 1-oxides showed greater thermal stability, but at 700-800 °C decomposition of the 4,5-dimethyl compound 25b lead to 1,2-di(5-methyl-2-phenyl- 1,2,3-triazol-2-yl)ethane as the major product; attempts to trap acetonitrile oxide were unsuccessful. ARKAT USA, Inc.
Regio- and stereochemistry of [2 + 2] photocycloadditions of imines to alkenes: A computational and experimental study
Sampedro, Diego,Soldevilla, Alberto,Campos, Pedro J.,Ruiz, Roberto,Rodriguez, Miguel A.
scheme or table, p. 8331 - 8336 (2009/04/11)
(Chemical Equation Presented) The [2 + 2] photocycloaddition of isoxazolines to alkenes has been studied by means of CASPT2/6-31G*// CASSCF/6-31G*. The reaction outcome is influenced by the relative ratio of imine deactivation and photocycloaddition. Anal
An improved synthesis of isoxazolines based on Tprssell's procedure
Nagarajan, A.,Pillay, M. Krishna
, p. 471 - 474 (2007/10/02)
Isoxazolines (1-29) have been prepared in 65-75percent yield by cycloaddition of alkenes to benzonitrile oxide, 4-chlorobenzonitrile oxide and 3-nitrobenzonitrile oxide generated in situ from the respective araldoximes.A number of new isoxazolines such as
Reaction of Hydroximic Chlorides with Hexabutylditin. A Mild Method for Generation and Cycloaddition of Nitrile Oxides.
Kim, Byeang Hyean
, p. 1199 - 1206 (2007/10/02)
A new method for the in situ generation of nitrile oxides is reported.The reaction conditions are mild and neutral.
