N-Thiocyanatosaccharin (R) was readily prepared from the sweet additive Saccharin in two steps with a 71% overall yield. By applying this new reagent to diverse nucleophiles such as benzothiophenes, indoles, oxindoles, aromatic amines, phenols, β-keto carbonyl compounds, and aromatic ketones, a novel electrophilic thiocyanation reaction was achieved with high yields (up to 99%). The potential recycling of Saccharin, the wide scope of substrates, and the mild reaction conditions made this protocol much more practical.
A new electrophilic thiocyanation reagent, N-thiocyanatophthalimide, was synthesized and applied to the first example of catalytic asymmetric electrophilic α-thiocyanation of various cyclic β-ketoesters by the bifunctional cinchona alkaloid catalysis. Thus, a variety of chiral α-thiocyanato β-ketoesters with a quaternary carbon center have been achieved in excellent yields (up to 99%) and high enantioselectivities (up to 94% ee) in a convenient manner.
The direct electrophilic α-cyanation of β-keto esters and amides has been developed using a hypervalent iodine benziodoxole-derived cyano reagent. The procedure is accomplished within 10 min and without the use of any catalyst in DMF, at room temperature. Thus, the highly functionalized quaternary carbon-centered nitriles were produced in high to excellent yields.
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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