- Conjugate addition reactions of N -carbamoyl-4-pyridones and 2,3-dihydropyridones with grignard reagents in the absence of Cu(I) Salts
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N-Boc- and N-ethoxycarbonyl-4-pyridones and the resulting 2,3-dihydropyridones undergo 1,4-addition reactions with Grignard reagents in the presence of chlorotrimethylsilane (TMSCl) or BF3·Et 2O in excellent yields. Copper catalysis is not required, and mechanistic considerations suggest that the reaction is proceeding by a conjugate addition pathway rather than by a pathway involving 1,2-addition to an intermediate pyridinium ion. TMSCl-mediated conjugate addition of Grignard reagents to 2-substituted-2,3-dihydropyridones gives the trans-2,6-disubstitued piperidinones stereoselectively, while cuprate reagents give either the trans or cis diastereomers or mixtures.
- Guo, Fenghai,Dhakal, Ramesh C.,Dieter, R. Karl
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p. 8451 - 8464
(2013/09/24)
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- Transannular and intermolecular interactions between chalcogen atoms: Syntheses and properties of dichalcogena dications and trichalcogena hypervalent dications
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Intramolecular (transannular) and intermolecular through-space interactions between chalcogen atoms have been described. This account includes the following three topics. (1) Various types of bis-chalcogenides and their mono-oxides, which have the two chalcogen atoms in close proximity in a molecule, give the dichalcogena dications upon the oxidation with two equivalents of NOBF4 or treatment with one equivalent of triflic anhydride (Tf2O). The stability of the dichalcogena dications increases in the order S N1 type reaction to form chalcogenachalcogenonium salts and alkyl cations. (2) The reaction of 2,6-bis[(phenylthio- or phenylseleno)methyl]phenyl phenyl telluride or the corresponding Te-oxide with NOBF4 or Tf2O affords the positively-charged hypervalent species, dicationic telluranes. Dicationic telluranes can be prepared by the remote oxidation through π-conjugation. The stable sulfenium cation can be isolated by taking advantage of 2,6-bis[(dimethylamino)methyl]phenyl ligand. (3) The remote oxygen migration and Pummerer reactions of p-bis(methylthio)-aromatic mono-oxides are discussed in light of an intermolecular through-space interaction between sulfur atoms, and a cyclic bis(dithia dication) dimer is proposed as an intermediate.
- Furukawa, Naomichi,Kobayashi, Kenji,Sato, Soichi
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p. 116 - 126
(2007/10/03)
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- SYNTHESIS OF TRIFLATE AND CHLORIDE SALTS OF ALKYL N,N-BIS(2,2,2-TRIFLUOROETHYL)AMINES
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Triflate and chloride salts have been prepared in high yield by using the triflate displacement reaction.
- Anderson, Gloria L.,Harruna, Issifu
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p. 111 - 114
(2007/10/02)
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