Annulation

About: Annulation is a research topic. Over the lifetime, 10152 publications have been published within this topic receiving 189701 citations.

Highly Enantioselective [3+2] Annulation of Morita–Baylis–Hillman Adducts Mediated by L‐Threonine‐Derived Phosphines: Synthesis of 3‐Spirocyclopentene‐2‐oxindoles having Two Contiguous Quaternary Centers

Abstract: The Morita—Baylis—Hillman (MBH) carbonates (II), (IV), and (VII) serve as C3 synthons in asymmetric [3 + 2] annulation reactions to give a series of 3-spirocyclopentene-2-oxindoles with two contiguous quaternary centers such as (III), (V), or (VIII) as present in various alkaloids.

Mild Rh(III)-catalyzed C-H activation and annulation with alkyne MIDA boronates: short, efficient synthesis of heterocyclic boronic acid derivatives.

Abstract: Taking advantage of Rh(III)-catalyzed C–H activation reactions, we have developed a mild, short, and efficient method for the synthesis of bench-stable 3-isoquinolone MIDA boronates. The reaction is practical and scalable. The product formed has been applied in the Suzuki–Miyaura reaction with high efficiency. This strategy has also been successfully expanded to the synthesis of MIDA boronate functionalized heterocycles such as isoquinoline, pyrrole, and indole.

Catalytic C−H Bond Functionalization with Palladium(II): Aerobic Oxidative Annulations of Indoles

Abstract: A palladium-catalyzed aerobic oxidative annulation of indoles is described. We have demonstrated that a variety of factors influence these cyclizations, and in particular the electronic nature of the pyridine ligand is crucial. It is also remarkable that these oxidative cyclizations can proceed in good yield despite background oxidative decomposition pathways, testament to the facile nature with which molecular oxygen can serve as the direct oxidant for Pd(0). We have also shown that the mechanism most likely involves initial indole palladation (formal C−H bond activation) followed by migratory insertion and β-hydrogen elimination.

Mild aerobic oxidative palladium (II) catalyzed C-H bond functionalization: regioselective and switchable C-H alkenylation and annulation of pyrroles.

Abstract: A palladium catalyzed C−H bond functionalization system that operates under ambient and aerobic conditions can be used to alkenylate pyrroles with control of regioselectivty. A steric and electronic control strategy can be used to influence positional control in the C−H bond functionalization process that results in either the C2 or C3 alkenylated products. Air, molecular oxygen, or tBuOOBz can be used as reoxidant in this mild process, and the reaction works on a range of substrates. Finally a catalytic aerobic annulation strategy is described that can be controlled to produce cyclization at either the C2 or C3 positions, thus forming diverse pyrrole products.

Direct synthesis of pyridine derivatives.

Abstract: We describe a single-step conversion of various N-vinyl and N-aryl amides to the corresponding pyridine and quinoline derivatives, respectively. The process involves amide activation with trifluoromethanesulfonic anhydride in the presence of 2-chloropyridine followed by π-nucleophile addition to the activated intermediate and annulation. Compatibility of this chemistry with sensitive N-vinyl amides, epimerizable substrates, and a variety of functional groups is noteworthy.