Expedient and Diastereodivergent Assembly of Terpenoid Decalin Subunits having Quaternary Stereocenters through Organocatalytic Robinson Annulation of Nazarov Reagent

Abstract

We report an expedient approach to highly functionalized cis- and trans-decalines that could function as key structural subunits toward the synthesis of various classes of terpenoids. Key to the strategy is an organocatalyzed Robinson annulation reaction of the Nazarov reagent that affords chiral enone building blocks with high enantioselectivities. The quaternary carbon stereogenic center can direct the subsequent reactions and allow the rapid and diastereoconvergent assembly of complex decalines with contiguous stereocenters.

Organocatalytic Desymmetrisation of Fittig’s Lactones: Deuterium as a Reporter Tag for Hidden Racemisation

“…Moreover, installation of a binaphthyl element into the quinine squaramide provided the highest enantioselectivity in the series of benzyl-substituted catalysts (entry 9 vs. entries 3, 7, and 8). Importantly, this is in line with our previous findings on squaramide-promoted organocatalytic Robinson type annulation, 14 and suggests a direct role of the π-system in the mechanism of stereoinduction. It is also worth mentioning that quinine-derived catalysts 3c and 3e always afforded higher enantioselectivities than their pseudo-enantiomeric quinidine-derived catalysts 3f and 3g.…”

Study on the Catalytic Behavior of Bifunctional Hydrogen‐Bonding Catalysts Guided by Free Energy Relationship Analysis of Steric Parameters

“…Indeed, Soós et al. recently achieved an asymmetric Robinson annulation reaction with a CHNaph 2 ‐derived bifunctional organocatalyst …”

“…recently achieveda na symmetricR obinson annulation reaction with aC HNaph 2 -derivedb ifunctional organocatalyst. [34] We speculated that the above-mentioned FER relationship may be universal in similar tertiary-amine (thio)urea/squaramide systems. Thus, two set of catalyst systems were next inspected (Tables 3a nd 4, Figures9 and 10).…”

Total Syntheses of (−)‐Minovincine and (−)‐Aspidofractinine through a Sequence of Cascade Reactions

“…Recently, our group developed a strategy for the concise and diastereoselective synthesis of cis ‐ and trans ‐decaline subunits of terpenoids . Key to this strategy was an organocatalyzed Robinson annulation reaction that afforded a chiral enone building block with a quaternary stereogenic center.…”

“…Recently, our group developed a strategy for the concise and diastereoselective synthesis of cis-and trans-decaline subunits of terpenoids. [14] Key to this strategy was an organocatalyzed Robinson annulation reaction that afforded a chiral enone building block with a quaternary stereogenic center. As an outgrowth of these studies, we were intrigued to develop an analogous chiral building block 7, which might confer synthetic practicality in aspidospermane chemistry.…”