Stereospecific Synthesis of ( E)-5-Tetrasubstituted-ylidene-3,5-dihydro-4 H-imidazol-4-ones

An Alkyne-Isocyanide Cycloaddition/Boulton-Katritzky Rearrangement/Ring Expansion Reaction: Access to 9-Deazaguanines

An alkyne-isocyanide [3 + 2] cycloaddition followed by a Boulton-Katritzky rearrangement and a ring expansion is demonstrated. Different from the typical Boulton-Katritzky rearrangement, which forms five-membered ring products, the rearrangement-ring expansion method provides a mild, efficient, and atom-economical access to fused 9-deazaguanine structures in high yields.

Base-Promoted Tandem SNAr/Boulton-Katritzky Rearrangement: Access to [1,2,4]Triazolo[1,5-a]pyridines

A base-promoted tandem S_NAr/Boulton-Katritzky rearrangement is developed. It offers a simple and straightforward method for the formation of functionalized [1,2,4]triazolo[1,5-a]pyridines from 1,2,4-oxadiazol-3-amines or 3-aminoisoxazoles with 2-fluoropyridines.

Sc(OTf)3-Catalyzed Iodocyclization/Ritter-Type Amidation of N-Alkoxypropiolamides: A Synthetic Strategy for Isoxazol-3(2H)-ones

A Sc(OTf)₃-catalyzed iodocyclization/Ritter-type amidation of N-alkoxypropiolamides for the synthesis of 4-iodoisoxazol-3(2H)-ones bearing an amide group has been developed. This domino protocol allows the construction of a valuable heterocycle, isoxazol-3(2H)-one, as well as the introduction of two functional groups. The reaction has a broad substrate scope and can be carried out on a large scale. Control experiments suggest that Sc(OTf)₃ acts as a dual activator for both the iodocyclization and amidation steps. In addition, the N-alkoxy group in the substrate suppresses some of the side reactions.

The preparation of (4H)-imidazol-4-ones and their application in the total synthesis of natural products

(4H)-Imidazol-4-ones are an important scaffold for a variety of applications, including natural products, medicine, agriculture, and other applications. Over the years, there have been a number of preparations published for the synthesis of imidazol-4-ones. This review discusses the progress made on the synthesis of imidazol-4-ones, and their application towards the total synthesis of a range of imidazol-4-one containing natural products. Emphasis is made on areas of the field that still need progress.