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The wide abundance of γ-lactones in natural products and bioactive targets calls for suitable building blocks for their enantioselective synthesis. β,γ-Unsaturated γ-butenolides, commonly known as deconjugated butenolides, owing to their easy accessibility and highly reactive nature, have emerged as the synthon of choice during the past decade for the enantioselective synthesis of γ-lactones. Their compatibility under organocatalytic, metal-catalyzed as well as cooperative catalytic conditions has resulted in numerous enantioselective transformations involving deconjugated butenolides. These reactions not only led to enantioenriched γ-lactones, but also various other heterocycles and acyclic compounds through ring-opening and fragmentation of the parent butenolide ring. The purpose of this review is to provide a comprehensive treatise on the catalytic asymmetric reactions of deconjugated butenolides reported so far. This aspect is presented alongside the preparation and reactivity comparison of deconjugated butenolides with other competing synthons of γ-lactones. Limitations of the existing protocols and the possible scope for future development are also discussed. [ABSTRACT FROM AUTHOR]

The synthesis of pure fine chemicals for industrial purposes is one of the most attractive challenges of chemical research. The use of catalytic pathways mediated by palladium nanoparticles (PdNPs) for C–C bond formation is a useful way to obtain these kinds of compounds. To achieve this objective, the PdNPs can be efficiently loaded on a functionalized natural nanostructured support such as halloysite nanotubes (HNTs). Hybrid materials based on thiol functionalized halloysite nanotubes and highly cross-linked imidazolium salts were successfully developed and used for the stabilization of PdNPs. The HNT/Pd hybrids were thoroughly characterized from a physico-chemical point of view and tested as a catalyst in the Suzuki and Heck C–C coupling reactions under microwave irradiation to obtain innovative materials for fine chemicals synthesis. Catalytic tests highlighted the fact that the HNT/Pd hybrids show high performance and full recyclability (up to ten cycles) in both reactions. Regarding the Suzuki reaction, under the best experimental conditions, the remarkable values of a turnover number of 194 000 and a turnover frequency of 3 880 000 h−1 were achieved without metal contamination in the final products. [ABSTRACT FROM AUTHOR]

Highly efficient asymmetric vinylogous 1,6-Michael addition of α,β-unsaturated γ-butyrolactam to 3-methyl-4-nitro-5-alkenyl-isoxazoles and Michael addition to trichloromethyl ketones by using a chiral quinine-derived squaramide organocatalyst were described, giving products with high diastereo- and enantioselectivities (up to ＞25 : 1 dr and 96% ee). [ABSTRACT FROM AUTHOR]