5502-72-7Relevant articles and documents
Hydroheteroarylation of Unactivated Alkenes Using N-Methoxyheteroarenium Salts
Ma, Xiaoshen,Dang, Hester,Rose, John A.,Rablen, Paul,Herzon, Seth B.
supporting information, p. 5998 - 6007 (2017/05/04)
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.
Bismuth-substituted "sandwich" type polyoxometalate catalyst for activation of peroxide: Umpolung of the peroxo intermediate and change of chemoselectivity
Amanchi, Srinivasa Rao,Khenkin, Alexander M.,Diskin-Posner, Yael,Neumann, Ronny
, p. 3336 - 3341 (2015/06/16)
The epoxidation of alkenes with peroxides by WVI, MoVI, VV, and TiIV compounds is well established, and it is well accepted that the active intermediate peroxo species are electrophilic toward nucleophilic substrates. Polyoxotungstates, for example, those of the "sandwich" structure, [WZn(TM-L)2(ZnW9O34)2]q- in which TM = transition metal and L = H2O, have in the past been found to be excellent epoxidation catalysts. It has now been found that substituting the Lewis basic BiIII into the terminal position of the "sandwich" polyoxometalate structure to yield [Zn2BiIII2(ZnW9O34)2]14- leads to an apparent umpolung of the peroxo species and formation of a nucleophilic peroxo intermediate. There are two lines of evidence that support the formation of a reactive nucleophilic peroxo intermediate: (1) More electrophilic sulfoxides are more reactive than more nucleophilic sulfides, and (2) nonfunctionalized aliphatic alkenes and dienes showed ene type reactivity rather than epoxidation pointing toward "dark" formation of singlet oxygen from the nucleophilic intermediate peroxo species. Allylic alcohols reacted much faster than alkenes but showed chemoselectivity toward C-H bond activation of the alcohol and formation of aldehydes or ketones rather than epoxidation. This explained via alkoxide formation at the BiIII center followed by oxidative β-elimination.
Radical reduction of epoxides using a titanocene(III)/water system: Synthesis of β-deuterated alcohols and their use as internal standards in food analysis
Jimenez, Tania,Campana, Araceli G.,Bazdi, Btissam,Paradas, Miguel,Arraez-Roman, David,Segura-Carretero, Antonio,Fernandez-Gutierrez, Alberto,Oltra, J. Enrique,Robles, Rafael,Justicia, Jose,Cuerva, Juan M.
experimental part, p. 4288 - 4295 (2010/10/21)
We describe a comprehensive study into the Cp2TiCl-mediated reductive epoxide ring opening using either water as a hydrogen source or deuterium oxide as a deuterium source. The remarkable chemical profile of this reaction allows access to alcohols with anti-Markovnikov regiochemistry from different epoxides. The use of D2O as a deuterium source leads to an efficient synthesis of β-deuterated alcohols, including a deuterated sample of tyrosol, a bioactive compound contained in the leaves of the olive, which was successfully applied as an internal standard in food analysis.
