A Hofmann Rearrangement-Ring Expansion Cascade for the Synthesis of 1-Pyrrolines: Application to the Synthesis of 2,3-Dihydro-1H-pyrrolo[2,1-a]isoquinolinium Salts

Hypervalent Iodine Promoted Selective [2 + 2 + 1] Cycloaddition of Aromatic Ketones and Methylamines: A One-Pot Access to 1-Pyrrolines

Herein, a versatile highly regioselective three-component annulation of simple aromatic ketones and methylamines using a hypervalent iodine reagent for polyarylated 1-pyrrolines has been described in good to excellent yields. Meanwhile, unsymmetrical 1-pyrroline isomers could be realized and synthesized. Such an intriguing one-pot two-step tandem assembly strategy with green conditions and high regioselectivity shows predictable inspiration in related annulation reactions.

Synthesis of Pyrrolo[2,1-a]isoquinolinium Salts from 1-Pyrrolines and Alkynes via Rhodium-Catalyzed C-H Functionalization/N-Annulation Tandem Reaction

A convenient synthesis of pyrrolo[2,1-a]isoquinolinium salts from 1-pyrrolines and alkynes through rhodium-catalyzed C-H functionalization/N-annulation tandem reaction is described. The protocol features a good substrate tolerance, mild reaction conditions, and high yields of target products. Exploration of the alkyne scope unexpectedly revealed a novel labile functional group-promoted rhodium-catalyzed C-H functionalization/C-annulation/elimination cascade reaction of 1-pyrrolines with electron-deficient alkynes.

Iron-Catalyzed Ring Expansion of Cyclobutanols for the Synthesis of 1-Pyrrolines by Using MsONH3OTf

The synthesis of 1-pyrrolines from cyclobutanol derivatives and an aminating reagent (MsONH₃OTf) has been developed. This one-pot procedure achieves C-N bond/C═N bond formation via ring expansion. A series of 1-pyrroline derivatives are synthesized in moderate to good yields under mild conditions.

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

β-Hydroxyalkylphosphine sulfides undergo [1,3]- or [1,4]-sulfur atom phosphorus-to-carbon migration in the presence of Lewis or Brønsted acids. The direction of sulfur atom migration depends on the type of acid used for the reaction. In the presence of a Brønsted acid, mainly [1,3]-rearrangement is observed, whereas a Lewis acid catalyzes the [1,4]-sulfur migration. To gain insight into the mechanism of these transformations, the stereochemistry of these rearrangements have been tested, along with the conduction of some control experiments and DFT calculations.

Recent Advances in the Applications of the Intramolecular Suzuki Cross-coupling Reaction in Cyclization and Heterocyclization: An Update

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The palladium-catalyzed reaction of aryl halide and boronic acid for the formation of C–C bonds so-called Suzuki–Miyaura cross-coupling reaction has many applications in Modern Synthetic Organic Chemistry. In 2013, we emphasized the applications of the intramolecular Suzuki cross-coupling reaction in cyclization and heterocyclization. Due to a plethora relevant papers appeared in the chemical literature, herein, we wish to cover by updating our previous review, the applications of the intramolecular Suzuki cross-coupling reaction in cyclization and heterocyclization leading to various homocyclic and heterocyclic compounds reported during a period of 2013 to 2018.