Diastereoselective sulfur oxidation of 2-thio-3-chloroacrylamides

Synthesis and stereoselective oxidation of α-thio-β-chloropropenyloxazolidin-2-ones

“…We have recently shown that with simple chiral amide auxiliaries, some, albeit modest, diastereocontrol is possible. 11 Reaction of E-4 with 2 equivalents of Oxone® led to a diastereomeric ratio of 1 : 0.9 of the resulting sulfoxides 15a and 15b, indicating that efficient asymmetric induction from the more remote oxazolidinone auxiliary was not feasible (in contrast to Evans' work where the oxazolidinone was bonded directly to the sulfide). 10 The diastereomers 15a and 15b were easily separated by chromatography on silica gel.…”

“…We have recently shown that with simple chiral amide auxiliaries, some, albeit modest, diastereocontrol is possible. 11 The diastereoselective sulfur oxidation of chiral N-arylthio and N-(alkylthio)oxazolidinones has been investigated by Evans using a range of achiral oxidising reagents. 10 Although the diastereoselectivity was poor, the diastereomers were easily separated by fractional crystallisation or chromatography and reacted readily with a variety of Grignard reagents to afford chiral sulfoxides.…”

Selective β-oxidation of α-sulfanyl amides

“…10,11 We recently reported a highly efficient and stereoselective transformation of -sulfanyl amides to the corresponding -sulfanyl--chloroacrylamide derivatives on treatment with NCS. 12 Chemoselective and stereoselective oxidations of the -chloroacrylamides to the sulfoxide and sulfone levels of oxidation has extended the scope of this methodology, 13,14 and the dipolarophilic and dienophilic behaviour of the -chloroacrylamides has also been described. [15][16][17] The synthetic potential of the -chloroacrylamides as Michael acceptors in nucleophilic addition/substitution reactions has also been investigated, including addition of morpholine to yield -enaminoamides.…”

The influence of reaction conditions on the Diels–Alder cycloadditions of 2-thio-3-chloroacrylamides; investigation of thermal, catalytic and microwave conditions

“…The relative stereochemistry of the precursor sulfoxide was determined by X-ray crystallographic analysis of the diastereomeric (R,Rs)-3r. 19 Thus, asymmetric induction from the sulfoxide chiral auxiliary is very effective in the cycloaddition process, with complete diastereofacial control, albeit yielding endo and exo isomers.…”

“…We have described asymmetric and diastereoselective sulfur oxidation in these series, leading to enantioenriched sulfinyl derivatives of the -chloroacrylamides. 15,19 Based on earlier work by Garcia Ruano, excellent asymmetric induction is envisaged in cycloadditions due to the chiral sulfoxide moiety. 8,12,13 The intramolecular Diels-Alder cycloaddition of the -chloroacrylamide derivative 1 was reported by Jung and Street in 1984.…”