(S)-4-Isopropyl-5,5-dimethyl-1,3-oxazolidinethione as chiral auxiliary for the intramolecular sulfur transfer in α,β-unsaturated N-acylimides, promoted by NbCl5

Synthetic Applications of Sulfur-based Chiral Auxiliaries in Asymmetric Syntheses

“…N-Enoyl oxazolidinethiones and thiazolidinethiones can undergo an intramolecular conjugate addition of the sulfur atom in the presence of Lewis or Bronsted acid. [43][44][45][46] Although, the preferred conformation of this type of compounds is the anti-s-cis in solid state, the anti-s-trans conformation 28 is required for the intramolecular conjugate addition. Based on this precedent, we designed a cascade reaction by the addition of an aldehyde in the presence of TiCl4 or BF3•OEt2.…”

Facile and Regioselective Dealkylation of Alkyl Aryl Ethers Using Niobium(V) Pentachloride

“…The resulting residue was purified by flash column chromatography on silica gel (hexane/AcOEt, 1:12) to give a 1:1 mixture of 8f and 9f (82. 8 …”

“…For example, they are known to react with carbon-nitrogen, [1,2] carbon-oxygen [3,4] and carboncarbon multiple bonds [5,6] to give 1,2-dianion or radical species. On the other hand, recent studies of Nb V have focused on organic transformations in carbon-carbon bond formation which are typical Lewis acid-mediated reactions, [7][8][9] except for unique reactions such as cyclopropane formation [10] and dealkylative acylation. [11] We were interested in the strong Lewis acidity of Nb V , and started to investigate its unique reactivity.…”

Recent Applications of Niobium Catalysts in Organic Synthesis

“…Ortiz and co-workers have demonstrated that niobium pentachloride is an efficient catalyst in the asymmetric sulfur addition reaction of N-enoyl oxazolidinethiones yielding βmercapto products (Scheme 2) [8]. The N-enoyl oxazolidinethione 4 was prepared in several steps from S-valine and 6 directly from (1R,2S) norephedrine, followed by acylation with either crotonyl or cinnamoyl chloride.…”