An enantioselective nickel(0)-catalyzed reductive three-component coupling between aromatic aldehydes, norbornenes, and silanes affords directly silyl-protected indanol derivatives. A new bulky chiral C2-symmetric NHC (NHC = N-heterocyclic carbene) ligand basing on the 1,2-di(napthalen-1-yl)ethylene diamine backbone allows accessing the annulated products as single diastereoisomers in high enantioselectivity.

Cyclopentenones are versatile structural motifs of natural products as well as reactive synthetic intermediates. The nickel-catalyzed reductive [3+2] cycloaddition of α,β-unsaturated aromatic esters and alkynes constitutes an efficient method for their synthesis. Here, nickel(0) catalysts comprising a chiral bulky C1-symmetric N-heterocyclic carbene ligand were shown to enable an efficient asymmetric synthesis of cyclopentenones from mesityl enoates and internal alkynes under mild conditions. The bulky NHC ligand provided the cyclopentenone products in very high enantioselectivity and led to a regioselective incorporation of unsymmetrically substituted alkynes.

While investigating the effect of the Cassyrane (rac-3/4) substitution pattern on the odor of dienones, (3E,5E)-5-tertbutylocta-3,5-dien-2-one (34) was discovered as an orris odorant with the lowest threshold reported so far in the ionone family (0.036 ng/L air). Derivatives 35-37, which allowed some insight into the underlying structure-odor relationships, were synthesized by a sequence consisting of copper(I)-catalyzed Grignard reactions with acyl chlorides, cerium-and lanthanum-assisted Grignard reactions of the resulting products with the Grignard reagent 17, prepared from but-3-yn-2-ol, manganese(IV) oxide oxidation of the secondary hydroxy function, elimination of the tertiary hydroxy function via its mesylate, alanate reduction of the ynone moiety to the corresponding allylic alcohol, and concluding manganese(IV) oxide oxidation. Furthermore, the γ,δ-unsaturated 38-41, and the fully hydrogenated analogues 42-45 were synthesized, and evaluated for their olfactory properties.

The title reaction between norbornene derivatives, aromatic aldehydes, and silanes provides silyl protected indanol scaffolds as single diastereomers with high enantiomeric excess.

Cyclopentenones are versatile structural motifs of natural products as well as reactive synthetic intermediates. The nickel‐catalyzed reductive [3+2] cycloaddition of α,β‐unsaturated aromatic esters and alkynes constitutes an efficient method for their synthesis. Here, nickel(0) catalysts comprising a chiral bulky C1‐symmetric N‐heterocyclic carbene ligand were shown to enable an efficient asymmetric synthesis of cyclopentenones from mesityl enoates and internal alkynes under mild conditions. The bulky NHC ligand provided the cyclopentenone products in very high enantioselectivity and led to a regioselective incorporation of unsymmetrically substituted alkynes.