One-Pot Cycloisomerization/Hetero-Diels–Alder Reaction of 1,6-Enynes with Aldehydes Catalyzed by Rhodium and a Brønsted Acid

Formal nucleophilic pyrrolylmethylation via palladium-based auto-tandem catalysis: switchable regiodivergent synthesis and remote chirality transfer

Although nucleophilic benzylation-type reaction to introduce various aromatic systems into molecules has been widely explored, the related pyrrolylmethylation version remains to be disclosed. Reported herein is a palladium-catalysed multiple auto-tandem reaction between N-Ts propargylamines, allyl carbonates and aldimines in the presence of an acid, proceeding through sequential allylic amination, cycloisomerisation, vinylogous addition and aromatisation steps. A diversity of formal pyrrolylmethylated amine products were finally furnished efficiently. In addition, switchable regiodivergent 3-pyrrolylmethylation and 4-pyrrolylmethylation were realised by tuning catalytic conditions. Moreover, remote chirality transfer with readily available enantioenriched starting materials was well achieved with an achiral ligand, relying on diastereoselective generation of η2-Pd(0) complexes between Pd(0) and chiral 1,3-diene intermediates in the key vinylogous addition step. A few control experiments were conducted to elucidate the palladium-involved tandem reaction and regiodivergent synthesis.

Rhodium-Catalyzed Aryl Migratory/Decarbonylation of Diaryl Ketones via the Activation of Unstrained C–C Bonds

A Rh-catalyzed aryl migratory/decarbonylation of unstrained ketones has been developed. This viable transformation provides a complementary decarbonylative method using diaryl ketones to afford a variety of alkenylated heterocycles in good yields with moderate to good stereoselectivity and broad substrate scope. The synthetic utility of this protocol is also demonstrated by the conversion of the alkenylated heterocycles to tetrahydrocarbazole derivatives.

Aldehydes: magnificent acyl equivalents for direct acylation

From the viewpoint of meeting the current green chemistry challenges in chemical synthesis, there is a need to disseminate how the cocktail of acylation and activation can play a pivotal role in affording bioactive acylated products comprising substituted ketone motifs in fewer reaction steps, with higher atom-economy and improved selectivity. In recent years, a significant number of articles employing the title compounds "aldehydes" as magnificent acylation surrogates which are less toxic and widely applicable have been published. This review sheds light on the compounds use for selective acylation of arene, heteroarene and alkyl (sp3, sp2 and sp) C-H bonds by proficient utilization of the C-H activation strategy. Critical insights into selective acylation of diverse moieties for the synthesis of bioactive compounds are presented in this review that will enable academic and industrial researchers to understand the mechanistic aspects involved and fruitfully employ these strategies in designing novel molecules.

Diversified Cycloisomerization/Diels-Alder Reactions of 1,6-Enynes through Bimetallic Relay Asymmetric Catalysis

We report the combination of transition-metal-catalyzed diversified cycloisomerization of 1,6-enynes with chiral Lewis acid promoted asymmetric Diels-Alder reaction to realize asymmetric cycloisomerization/Diels-Alder relay reactions of 1,6-enynes with electron-deficient alkenes. A broad spectrum of chiral [5,6]-bicyclic products could be acquired in high yields (up to 99 %) with excellent diastereoselectivy (>19:1 dr) and enantioselectivity (up to 99 % ee).

Palladium(0)-catalyzed [2 + 2 + 1] cyclization of 1,6-enynes with vinyl bromides: a highly diastereoselective synthesis of tetrahydro-1H-cyclopenta[c]furans bearing two quaternary carbon centers

A new cascade process has been accomplished for the synthesis of tetrahydro-1H-cyclopenta[c]furans through palladium-catalyzed [2 + 2 + 1] cyclization of 1,6-enynes with vinyl bromides. Notably, the key feature of this transformation is the use of vinyl bromides as the C1 building block. Various functionalized tetrahydro-1H-cyclopenta[c]furans bearing two quaternary carbon centers could be obtained in good yields with excellent diastereoselectivities.