Origins of stereoselectivity in radical additions: reactions of alkenes and radicals bearing oxazolidine and thiazolidine amide groups

Opposite π-Face Selectivity for the DMD and m-CPBA Epoxidations of Chiral 2,2-Dimethyloxazolidine Derivatives of Tiglic Amides: Control by Steric Interactions versus Hydrogen Bonding

“…To rationalize the opposite sense in the diastereoselectivity observed herein for the epoxidation of the tiglic amides ( S ) -1 by DMD and m -CPBA (no other examples appear to be known for this pair of oxidants), it is necessary to know the preferred conformation of the starting amides. Although the favored conformation of the N -tigloyl fragment is syn with respect to the oxazolidine ring, analogous to the N -acryloyloxazolidines described by Kanemasa and Porter, the double bond is twisted with respect to the carbonyl group to avoid steric interactions with the substituent at the 4 position in the oxazolidine ring (Scheme ). This conformational orientation of the double bond with respect to the carbonyl group is general for methacrylate and tiglate derivatives of imides and amides since the planar rotamers ( s-trans and s-cis cannot be accommodated with the auxiliary for steric reasons .…”

Novel Organotellurium Heterocycles Derived From Bis(2‐Aminophenyl) Ditelluride

“…2‐Bromobutanoyl chloride , 2‐bromo‐2‐phenylacetyl chloride , bis(2‐aminophenyl) ditelluride, and bis(2‐amino‐5‐methylphenyl) ditelluride were prepared as previously reported. All other chemicals were purchased in reagent grade purity and used as received.…”

Diastereoselective C‐arylation of prochiral enolates by the SRN1 reaction

“…(4R,5S)-1,5-dimethyl-4-phenyl-3-(2V-phenylacetyl)-imidazolidin-2-one (1) was obtained quantitatively from the reaction of (4R,5S)-1,5-dimethyl-4-phenyl-imidazolidin-2-one with phenylacetyl chloride in dry CH 2 Cl 2 with Na 2 CO 3 at room temperature under argon. 5 (4R,5S)-1,5-dimethyl-4-phenyl-imidazolidin-2-one was prepared as described in the literature by starting from urea and ( -)-ephedrine hydrochloride. 6 General Procedure for the Reaction of Asymmetric Enolate 1 With Aryl Halides in Liquid Ammonia by the S RN 1 Mechanism First, 0.26 mmol of the corresponding metal (K, Na, Li) was added to 150 ml of distilled liquid ammonia.…”