An enantioselective thiocyanation
of oxindoles has been developed
for the first time using a bifunctional cinchona-derived organo-catalyst
and N-thiocyanatophthalimide as the electrophilic
thiocyanation source in the presence of 2-naphthol as the additive.
Various enantioenriched 3,3′-disubstituted oxindoles with SCN-containing
quaternary carbon stereocenters were synthesized under mild conditions
in high yields (up to 99%) and good enantioselectivities (up to 6:94
er).
The first electrophilic asymmetric selenocyanation has been achieved in the presence of Ni(OTf) 2 and (R,R)-DBFOX/Ph using N-selenocyanatosaccharin as the new selenocyanation reagent. Thus, a series of α-selenocyanato-βketo esters were synthesized with high yields (up to 99%) and good ee values (up to 92% ee). The readily preparation of the reagent and high enantioselectivity make this methodology much practical for the synthesis of chiral selenocyanates.
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