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An unprecedented thermodynamically unfavorable (4+1) deysmmetrizing spiroannulation through a thermodynamic enolate intermediate, enabling a single-step synthesis of ubiquitous scaffolds such as all-carbon chiral spirocycles, is disclosed. In this spiroannulation, we present a vinylogous organocatalytic enantioselective desymmetrizing (4+1) cycloaddition approach involving alkylidene malononitrile and cyclopent-1,3-dienone. This carbospiroannulation method produces functionally enriched spiro[4,4]nonane structures with three stereocenters, has presented good-to-high yields and enantiomeric ratios. Detailed DFT calculations reveal an intriguing reaction mechanism, which validates our observations.
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http://dx.doi.org/10.1002/chem.202500671 | DOI Listing |
Org Lett
May 2025
College of Chemistry and Pharmaceutical Engineering, Nanyang Normal University, Nanyang 473061, China.
Herein, a nickel-catalyzed α-alkenylation reaction of asymmetric cyclic ketones at the sterically hindered α-position with alkenes is disclosed. The high regioselectivity might originate from the acid-catalyzed enolization reaction, selectively generating the thermodynamically favored enol. The nickel catalyst facilitates the preferential alkenylation of polysubstituted enolates rather than monosubstituted enolates, thereby reversing the conventional regioselectivity of alkenylation at the α-position of ketones.
View Article and Find Full Text PDFChemistry
May 2025
Department of Chemistry, Indian Institution of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
An unprecedented thermodynamically unfavorable (4+1) deysmmetrizing spiroannulation through a thermodynamic enolate intermediate, enabling a single-step synthesis of ubiquitous scaffolds such as all-carbon chiral spirocycles, is disclosed. In this spiroannulation, we present a vinylogous organocatalytic enantioselective desymmetrizing (4+1) cycloaddition approach involving alkylidene malononitrile and cyclopent-1,3-dienone. This carbospiroannulation method produces functionally enriched spiro[4,4]nonane structures with three stereocenters, has presented good-to-high yields and enantiomeric ratios.
View Article and Find Full Text PDFFood Chem
June 2025
School of Food Science and Technology, State Key Laboratory of Marine Food Processing & Safety Control, National Engineering Research Center of Seafood, Dalian Polytechnic University, Dalian 116034, China. Electronic address:
Heat, light, and microwave treatments differentially modulate food flavor profiles through lipid oxidation, but the mechanistic distinctions remain unclear. This study monitored and compared lipid molecular species and flavor compounds in salmon oil processed by these methods via multi-omics technology. Thermal treatment yielded the highest concentrations of alkanes, alkenals, enols, and aldehydes (50.
View Article and Find Full Text PDFJ Am Chem Soc
March 2025
Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (R.O.C.).
The enantioselective protonation of prochiral enolates is an ideal and straightforward platform to synthesize stereodefined α-tertiary esters, which are recurring motifs in a myriad of biorelevant molecules and important intermediates thereof. However, this approach remains onerous, particularly when dealing with α-unactivated esters and related acids, as enantioinduction on the nascent nucleophile necessitates peremptory reaction conditions, thus far only achieved via preformed enolates. A complementary and contra-thermodynamic catalytic strategy is herein described, where a transient photoenol, in the form of a ketene hemiacetal, is enantioselectively protonated with a chiral phosphoric acid (CPA).
View Article and Find Full Text PDFLife (Basel)
December 2024
Department of Chemistry & Biochemistry, University of San Diego, San Diego, CA 92110, USA.
Using computational methods, we examine if the presence of HS can tame the unruly formose reaction by generating a free energy map of the reaction thermodynamics and kinetics of sulfur analogs within the core cycle. With mercaptoaldehyde as the linchpin C species, and feeding the cycle with CHO, selected aldol additions and enolizations are kinetically more favorable. Thione formation is thermodynamically less favored compared to aldehydes and ketones, but all these species can be connected by enolization reactions.
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