139192-49-7Relevant articles and documents
Stereoselective radical addition of an acetal to sterically tuned enantiomerically pure N-sulfinyl imines
Akindele, Tito,Yamada, Ken-Ichi,Sejima, Takumi,Maekawa, Masaru,Yamamoto, Yasutomo,Nakano, Mayu,Tomioka, Kiyoshi
experimental part, p. 265 - 269 (2010/07/08)
Enantiomerically enriched sulfonamides were synthesized by the radical addition of an acetal to enantiomerically pure N-sulfinyl imines using dimethylzinc-air and boron trifluoride diethyl etherate. Higher levels of stereocontrol were observed by using a mesitylenesulfinyl group. Furthermore, an amine and an amino alcohol with high enantiomeric purity were obtainable from the sulfonamide product.
Lithiated 4-isopropyl-3-(methylthiomethyl)-5,5-diphenyloxazolidin-2-one: A chiral formyl anion equivalent for enantioselective preparations of 1,2-diols, 2-amino alcohols, 2-hydroxy esters, and 4-hydroxy-2-alkenoates
Gaul,Schaerer,Seebach
, p. 3059 - 3073 (2007/10/03)
The heterocyclic compound specified in the title (and readily prepared from commercial precursors) has a sterically protected C=O group, so that direct lithiation by BuLi at the exocyclic CH2 group is possible (3 → Li-3). The lithiated N,S-acetal derivative (Li-3) adds diastereoselectively to aldehydes (Table 2), unsymmetrical ketones (Table 3), chalcone (1,4-addition, Scheme 2), and N-phosphinoyl-and N-sulfonylimines (Table 4). Protection of the newly formed OH groups (Scheme 3) and/or MeS/OH displacement by Hg(O2CCF3)2 in aqueous THF/acetonitrile converts the N,S-acetals into hemiaminals (→ 20) which, in turn, are readily cleaved to aldehydes, with recovery of the chiral auxiliary (1, Scheme 4). The aldehydes (especially those lacking α-carbonyl hydrogens) may be isolated, or they are trapped in situ by reduction to (selectively protected) diols or amino alcohols, by addition of Grignard or Li reagents, which provides diols with two stereogenic centers, by oxidation to give 2-hydroxy esters, or by olefination to provide 4-hydroxy-2-alkenoates (Scheme 5). The scope and limitations of the new, overall enantioselective transformation are determined, and the readily recovered chiral auxiliary used is compared with oxazolidinones of other substitution patterns (Scheme 7). The configuration of a number of products has been assigned by single-crystal X-ray diffraction (cf. Figure 5). These structures and similarities of NMR data led to configurational assignment of the other products (see formulas in the schemes and tables) by analogy. A simple mechanistic model for the stereochemical course of the addition of Li-3 to aldehydes and ketones is presented (Figure 6).
Diastereoselective synthesis of enantiomerically pure 3-organosulfonyl-2-(2-oxocycloalkyl)-1,3-oxazolidines from 2-formylcycloalkanones and β-aminoalkanols
Hoppe,Hoffmann,Gartner,Krettek,Hoppe
, p. 1157 - 1162 (2007/10/02)
The title compounds (3-arylsulfonyl- or 3-mesyl-2-(2-oxocycloalkyl)-1,3-oxazolidines) belonging to two different diastereomeric series, are prepared selectively by variation of the condensation conditions. By this, the chiral information of the 2-amino-1-
