- Nickel-catalyzed cyclization of ortho-iodoketoximes and ortho-iodoketimines with alkynes: Synthesis of highly substituted isoquinolines and isoquinolinium salts
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A convenient method for the synthesis of highly substituted isoquinolines and isoquinolinium salts by the nickel-catalyzed cyclization of ortho-haloketoximes and -ketimines, respectively, with alkynes is described. The reaction of ortho-haloketoximes and various alkynes in the presence of [Ni(PPh3)2Br2] and zinc powder in a mixture of acetonitrile and tetrahydrofuran at 80 °C for 15 hours gave 1,3,4-trisubstituted isoquinoline products in moderate to excellent yields and high regioselectivity. The corresponding isoquinoline N-oxide was found to be the intermediate in the cyclization reaction pathway. In contrast, the reaction of ortho-haloketimines and alkynes under similar catalytic conditions in tetrahydrofuran at 70 °C for two hours gave 1,2,3,4-tetrasubstituted isoquinolinium salts in good to excellent yields. In the nickel of time: ortho-Haloketoximes and -ketimines undergo [4+2] cyclization reactions with alkynes, catalyzed by nickel complexes to give highly substituted isoquinolines and isoquinolinium salts, respectively, in good to excellent yields (see scheme).
- Shih, Wei-Chun,Teng, Chu-Chun,Parthasarathy, Kanniyappan,Cheng, Chien-Hong
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supporting information; experimental part
p. 306 - 313
(2012/05/05)
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- OXIDATIVE CYCLIZATION OF HALOBENZOPHENONE OXIMES TO 4,2'-IODONIA-3-PHENYL-1,2-BENZISOXAZOLE SALTS
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It is shown that the syn oximes of o-iodo- and o-, m-, and p-bromobenzophenones, under the influence of K2S2O8 in concentrated H2SO4, form the corresponding 3-aryl-1,2-benzisoxazoles as a result of oxidative cyclization. 3-(2-Iodophenyl)-1,2-benzisoxazole is oxidized by peracetic acid to the iodoso derivative which, upon heating in concentrated H2SO4, undergoes cyclization to the 4,2'-iodonia-3-phenyl-1,2-benzisoxazole cation.The iodide, bromide, and tetrafluoroborate of this cation were isolated.
- Tolstaya, T. P.,Egorova, L. D.,Lisichkina, I. N.
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p. 392 - 396
(2007/10/02)
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