Asymmetric Michael addition of glycine imines via quaternary ammonium ion catalysis

Efficient Synthesis of 11C‐Acrylesters, 11C‐Acrylamides and Their Application in Michael Addition Reactions for PET Tracer Development

“…[15] Generally, lower temperatures are favored in PTC reactions to enhance stereoselectivity. [18,27,28] This is presumably caused by the reaction time, since in carbon-11 radiosynthesis only rapid reactions can be considered because of the short half-life of 20 min, whereas in organic chemistry longer reaction times are feasible. Because of a solid-liquid phase reaction taking place, a sufficient interfacial area between the two phases needs to be created by vigorous stirring.…”

Recent Developments in Enantioselective Phase Transfer Catalysis Using Chiral Ammonium Salts

“…However, a simple modification of the nature of the substrate (a benzhydryl ester instead of a t-butyl ester) afforded much higher selectivity (up to 94%) and, after a simple hydrogenation reaction (H 2 , Pd/C), the synthesis of non-racemic 2,5-disubstituted pyrrolidines was readily achieved [80].…”

“…We have already mentioned that the benzhydryl analogue of ester 1 led, in one instance, to a higher level of selectivity than the t-butyl ester [80]. Other analogous substrates of 1 were prepared by changing the carboxyl functional group or the nitrogen protecting group.…”

Catalytic Asymmetric Synthesis of 3‐Substituted Proline Derivatives by Using Phase‐Transfer‐Catalyzed Conjugate Addition

“…At first, we examined the asymmetric conjugate addition of 2 [10] to cinnamaldehyde catalyzed by chiral phase-transfer…”

“…The absolute configuration of 6 was determined by an X-ray diffraction analysis of a complex of 6 with 4-bromophenylacetic acid. [21] We further attempted the asymmetric conjugate addition of 2 to a,b-unsaturated ketones, [8,10] such as ethyl vinyl ketone and chalcone, catalyzed by (S)-5 b or (S,S)-9 c (Scheme 7). In both cases, (S)-5 b gave better enantioselectivity than (S,S)-9 c.…”