The first highly diastereo- and enantioselective synthesis of 2,4-disubstituted imidazolidines has been developed via a formal [3+2] cyclization reaction. Bidentate aminomethyl enones and N-tosyl imines were used as the reaction partners in the reaction. Bifunctional squaramide catalysts were found to be efficient for this reaction and few transformations of the products have been demonstrated.

ortho-Quinone methides are important structures, having a cyclohexadiene core bearing an exocyclic alkylidiene and carbonyl functionality at the ortho-position, and are widely used as essential intermediates in organic synthesis. These reactive intermediates are also used as important building blocks for the construction of a variety of heterocycles by hetero Diels-Alder, electrocyclization reactions. Moreover, ortho-quinone methides are a class of electrophiles, serving as Michael acceptors leading to conjugate additions with various nucleophiles. In general, ortho-Quinone methides have transient existence and are highly reactive in nature. ortho-Quinone methides have been generated in situ from stable precursors using either Brønsted acids or Brønsted bases. In the last few years, ortho-quinone methides have been explored as imperative class of substrates in various bifunctional organocatalysts mediated asymmetric conjugate additions, cycloannulation, acyl-transfer reaction, thiolation and hydrophosphination reactions. This review illustrates recent advancements of asymmetric transformations of ortho-quinone methides with bifunctional H-bonding organocatalysts.[a] S.

The first organocatalytic asymmetric reaction employing 3,4‐dihydro‐2‐quinolone has been developed leading to the synthesis of biologically important 3,3‐disubstituted‐dihydro‐2‐quinolones. Cinchona alkaloid derived bifunctional amino‐thiourea catalysts were found to be the best catalysts. The products were obtained in high enantio‐ and good diastereoselectivities and also few synthetic transformations have been demonstrated.magnified image

An organocatalytic asymmetric cascade reaction has been developed between N-tosyl aminomethyl enones and trans-α-cyano-α,β-unsaturated ketones for the synthesis of highly substituted pyrrolidines having a stereogenic quaternary centre at the 3-position.

An organocatalytic enantioselective Mannich reaction involving dihydro‐3‐carboalkoxy‐2‐quinolone and preformed N‐Boc imines has been developed leading to the formation of biologically important 3,3‐disubstituted‐dihydro‐2‐quinolones. Cinchona alkaloid derived thiourea catalysts were found to be effective for this reaction. The desired products were obtained in good yields with good to high enantioselectivities and moderate diastereoselectivities.