TEMPO-catalyzed synthesis of 5-substituted isoxazoles from propargylic ketones and TMSN<sub>3</sub>
作者:Yan He、Yu-yang Xie、Ying-chun Wang、Xiao-min Bin、Da-chao Hu、Heng-shan Wang、Ying-ming Pan
DOI:10.1039/c6ra11099a
日期:——
A novel and efficient TEMPO-catalyzed synthesis of 5-substituted isoxazoles from propargylic ketones and TMSN3 via a radical mechanism process is described. This methodology provides an easy access to a variety of useful 5-substituted isoxazoles from simple and readily available propargylic ketones and TMSN3 in good to excellent yields. A plausible reaction mechanism for this process is proposed.
Reactivity in the gas phase. Behaviour of isoxazoles under negative ion chemical ionization conditions
作者:Antonio Guarna、Gloriano Moneti
DOI:10.1002/oms.1210240709
日期:1989.7
Abstract[M H+]− ions of isoxazole (la), 3‐methylisoxazole (1b), 5‐methylisoxazole (1c), 5‐phenylisoxazole (1d) and benzoylacetonitrile (2a) are generated using NICI/OH− or NICI/NH2− techniques. Their fragmentation pathways are rationalized on the basis of collision‐induced dissociation and mass‐analysed ion kinetic energy spectra and by deuterium labelling studies. 5‐Substituted isoxazoles 1c and 1d, after selective deprotonation at position 3, mainly undergo N O bond cleavage to the stable α‐cyanoenolate NC CH CR O− (R = Me, Ph) that fragments by loss of RCN, or RH, or H2O. The same α‐cyanoenolate anion (R = Ph) is obtained from 2a with OH−, or NH2−, confirming the structure assigned to the [M H+]− ion of 1d, On the contrary, 1b is deprotonated mainly at position 5 leading, via NO and C(3)C(4) bond cleavages, to HC ≡ C O − and CH3CN. Isoxazole (1a) undergoes deprotonation at either position and subsequent fragmentations. Deuterium labelling revealed an extensive exchange between the hydrogen atoms in the ortho position of the phenyl group and the deuterium atom in the α‐cyanenolate NC CD = CPh O−.
Photochemistry of 4- and 5- phenyl substituted isoxazoles
作者:James W. Pavlik、Heather S T. Martin、Karen A. Lambert、Jennifer A. Lowell、Vikki M. Tsefrikas、Cheryl K. Eddins、Naod Kebede
DOI:10.1002/jhet.5570420215
日期:2005.3
zole (25) respectively. In addition to phototransposition, isoxazoles 4, 10, and 23 also underwent photo-ring cleavage to yield benzoylacetonitrile (9), α-benzoylpropionitrile (15), and aceto-α-phenylacetonitrile (26) respectively. Irradiation of 5-phenyl-3-(trifluoromethyl)isoxazole (16) in acetonitrile led to 5-phenyl-2-(trifluoromethyl)oxazole (17), the P4 phototransposition product. Irradiation