Enantioselective Synthesis of Spirooxindole α‐exo‐Methylene‐γ‐butyrolactones from 3‐OBoc‐Oxindoles

Abstract

Chiral Lewis bases facilitated the synthesis of highly functionalized spirooxindoles containing α‐exo‐methylene‐γ‐butyrolactones in high yields (76–92 %) and excellent enantioselectivities (up to 98 % ee) at ambient temperature.

Zinc‐Mediated Efficient and Selective Reduction of Carbonyl Compounds

“…NaBH 4 is the commonly used reagent for the selective reduction of isatin derivatives at the C3 position; however, 5‐halo‐substituted isatins gave the corresponding 3‐hydroxyindolines in poor yields. Recently, a combination of CeCl 3 and NaBH 4 has been developed for the efficient reduction of 5‐halo‐substituted isatins . In contrary, our reaction conditions (3 equiv.…”

Electrophilic Amide Allylation of 3‐Heterosubstituted Oxindoles: A Route to Spirocyclic 2‐Oxindoles Containing the α‐Methylene‐γ‐butyrolactam Structure

“…At the same time, for other substrates such as N ‐phenyl and unsubstituted variants 4b and 4c , the reactions still occurred efficiently to produce 2f and 2g in very high yields of >99 and 94 %, respectively (Table , entries 7 and 8). Furthermore, it is interesting to note that the catalysis showed adequate levels of reactivity toward a broad range of 3‐heterosubstituted oxindoles, even when catalyst‐poisonous 3‐phenylthio derivatives 4f , h were used, thereby affording 2h – l with high catalyst productivity (Table , entries 9–13).…”

“…Elemental analyses were performed with JSL Model JM 10 instruments. 3‐Heterosubstituted oxindoles 4a , d , e , g , and 4h were prepared according to the literature procedure …”

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

“…Similarly, Kesavan and co-workers reacted 3- O -Boc-oxindoles 23 with MBH carbonates 22 to generate a range of spirocyclic scaffolds containing α- exo -methylene-γ-butyrolactone 24 – again using β-ICPD ( Scheme 6 ) [ 30 ].…”