- Hydroheteroarylation of Unactivated Alkenes Using N-Methoxyheteroarenium Salts
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We report the first reductive coupling of unactivated alkenes with N-methoxy pyridazinium, imidazolium, quinolinium, and isoquinolinium salts under hydrogen atom transfer (HAT) conditions, and an expanded scope for the coupling of alkenes with N-methoxy pyridinium salts. N-Methoxy pyridazinium, imidazolium, quinolinium, and isoquinolinium salts are accessible in 1-2 steps from the commercial arenes or arene N-oxides (25-99%). N-Methoxy imidazolium salts are accessible in three steps from commercial amines (50-85%). In total 36 discrete methoxyheteroarenium salts bearing electron-donating, electron-withdrawing, alkyl, aryl, halogen, and haloalkyl substituents were prepared (several in multigram quantities) and coupled with 38 different alkenes. The transformations proceed under neutral conditions at ambient temperature, provide monoalkylation products exclusively, and form a single alkene addition regioisomer. Preparatively useful and complementary site selectivities in the addition of secondary and tertiary radicals to pyidinium salts are documented: harder secondary radicals favor C-2 addition (2->10:1), while softer tertiary radicals favor bond formation to C-4 (4.7->29:1). A diene possessing a 1,2-disubstituted and 2,2-disubstituted alkene undergoes hydropyridylation at the latter exclusively (61%) suggesting useful site selectivities can be obtained in polyene substrates. The methoxypyridinium salts can also be employed in dehydrogenative arylation, borono-Minisci, and tandem arylation processes. Mechanistic studies support the involvement of a radical process.
- Ma, Xiaoshen,Dang, Hester,Rose, John A.,Rablen, Paul,Herzon, Seth B.
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supporting information
p. 5998 - 6007
(2017/05/04)
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- Insights into the mechanistic and synthetic aspects of the Mo/P-catalyzed oxidation of N-heterocycles
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A Mo/P catalytic system for an efficient gram-scale oxidation of a variety of nitrogen heterocycles to N-oxides with hydrogen peroxide as terminal oxidant has been investigated. Combined spectroscopic and crystallographic studies point to the tetranuclear Mo4P peroxo complex as one of the active catalytic species present in the solution. Based on this finding an optimized catalytic system has been developed. The utility and chemoselectivity of the catalytic system has been demonstrated by the synthesis of over 20 heterocyclic N-oxides.
- Larionov, Oleg V.,Stephens, David,Mfuh, Adelphe M.,Arman, Hadi D.,Naumova, Anastasia S.,Chavez, Gabriel,Skenderi, Behije
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p. 3026 - 3036
(2014/05/06)
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- Experimental and theoretical molecular and electronic structures of the N-oxides of pyridazine, pyrimidine and pyrazine
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The structures of pyridazine N-oxide, pyrimidine N-oxide and pyrazine N-oxide have been determined by X-ray diffraction for the first time. Comparison with theoretical predictions of the equilibrium structures using the B3LYP method together with a cc-pVTZ basis set, show close agreement with the structural parameters observed, and experimental dipole moments, which suggests that the charge distribution is realistic. An 'atoms in molecules' (AIM) analysis of the computed wave-functions shows total electron densities rather different from the classical picture of a dative bond, whereas the same wave-functions subjected to Mulliken analysis show a more conventional view of the electron distribution. This latter procedure allows a bond dipole analysis of the N-oxide charge distribution.
- Aitken, R. Alan,Fodi, Bernd,Palmer, Michael H.,Slawin, Alexandra M.Z.,Yang, Jing
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experimental part
p. 5845 - 5851
(2012/09/08)
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- Use of N-oxide compounds in coupling reactions
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Metal-catalyzed coupling process comprising reacting a compound of general formula 1 with a compound A-X, to obtain a compound of general formula 2, which may further be converted to a compound of general formula 3
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Page/Page column 18
(2008/12/05)
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- One step conversion of heteroaromatic-N-oxides to imidazolo-heteroarenes
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(Chemical Equation Presented) Various pyridine-, quinoline-, isoquinoline-, and pyrimidine-N-oxides were converted to their corresponding α-imidazoloheteroarenes in good yield by treatment with sulfuryl diimidazole in nonpolar solvents at elevated tempera
- Keith, John M.
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p. 327 - 330
(2008/04/12)
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- Palladium-catalyzed cross-coupling reactions of diazine N-oxides with aryl chlorides, bromides, and iodides
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New aspects of N-oxides: Pyrazine, pyridazine, and pyrimidine N-oxides are regioselectively arylated with aryl iodides, bromides, and chlorides in the presence of a palladium catalyst (see scheme). The resulting products can be deoxygenated in high yield
- Leclerc, Jean-Philippe,Fagnou, Keith
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p. 7781 - 7786
(2007/10/03)
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- OXIDATION OF 2,4-DISUBSTITUTED PYRIMIDINES WITH ORGANIC PERACIDS
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While 4,6-disubstituted (alkyl, aryl, alkoxyl) pyrimidines easily afforded the corresponding mono-N-oxides with hydrogen peroxide in glacial acetic acid, pyrimidine derivatives whose 6-position is free, are partly oxidatively degradated during N-oxidation reaction.The oxidation of the latter compounds under the above conditions gave 2,4-disubstituted imidazoles together with their mono-N-oxides.A likely mechanism of this ring-contraction and the improved conditions for the synthesis of the N-oxides are also described.
- Yamanaka, Hiroshi,Ogawa, Shigeru,Sakamoto, Takao
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p. 573 - 576
(2007/10/02)
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- Process for the production of 2-alkyl or 2-cycloalkyl-4-methyl-6-hydroxypyrimidines
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Production of 2-alkyl or 2-cycloalkyl-4-methyl-6-hydroxy pyrimidines by first reacting diketene and lower alkanoic or cycloalkanoic acid amides in the presence of catalytic amounts of Lewis bases or Lewis or Bronsted acids, followed by treating the N-acetoacetyl (lower) alkanoic or cycloalkanoic acid amide intermediates with ammonia in the presence of acid catalysts.
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- Pyrimidyl thio- and dithio-phosphoric acid esters
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Pyrimidyl-thio and dithio-phosphoric acid esters of the formula STR1 wherein R1 represents a C3 to C6 cycloalkyl group, R2 and R3 each represent a C1 to C5 alkyl group and X and Y each represent oxygen or sulfur, Processes for their manufacture, and their use in pest control.
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