The development of a new class of hydrazide type organocatalyst, (4R,5R)-1,3-bis(isopropylamino)-4,5-dihenylimidazolidin-2-one 2a, for enantioselective Diels-Alder reactions between cyclopentadiene and α,β-unsaturated aldehydes are presented. The new organocatalyst 2a promoted the reaction, affording Diels-Alder adducts in good yields with good levels of enantioselectivity.

The stereochemical course of electrophilic substitutions of α‐nitrile metallocarbanions was investigated through the deprotonation of enantioenriched α‐amino‐ and α‐oxynitriles bearing a carbamoyl or methoxycarbonyl group in the presence of an electrophile. The results suggested that the dipole‐stabilizing substituents not only affected the configurational stability and chemical reactivity of the α‐nitrile metallocarbanions but could also change the steric course of the electrophilic substitution (retention vs. inversion). Whereas the reaction of an α‐aminonitrile bearing a dimethylaminocarbonyl group on the nitrogen atom with lithium hexamethyldisilazane in the presence of PhCOCl resulted in the formation of a retention product (93:7), the reaction of an α‐aminonitrile bearing a methoxycarbonyl group was reversed in favor of the inversion product (37:63). Thus, the methoxycarbonylamino group increased the degree of planarization of the anionic center with maintenance of the planar chirality more than the ureido group, which led to preferential attack of the electrophile from the rear face.

A Novel Hydrazide Type Organocatalyst for Enantioselective Diels-Alder Reactions. -A new class of hydrazide-type organocatalyst is successfully applied in asymmetric Diels-Alder cycloadditions of α,β-unsaturated aldehydes (II) and (V) towards cyclopentadiene. Enantioselectivities of up to 96% e.e. are achieved. The reaction mechanism is discussed in detail. -(SUZUKI*, I.; ANDO, M.; SHIMABARA, R.; HIRATA, A.; TAKEDA, K.; Org. Biomol. Chem. 9 (2011) 8, 3033-3040, http://dx.doi.org/10.1039/c0ob01138j ; Hiroshima Univ., Minami, Hiroshima 734, Japan; Eng.) -Mischke 34-025