Improved and expanded one-pot, two-component Boulton-Katritzky syntheses of N–N bond containing bicyclic heterocycles

Synthesis of Indazoles via N-N Bond-Forming Oxidative Cyclization from 2-Aminomethyl-phenylamines

Herein we report a method for the synthesis of indazoles from readily available 2-aminomethyl-phenylamines via N-N bond-forming oxidative cyclization. Inspired by indazole formation initially observed as a side product by N. Coskun et al. we developed a robust protocol to access indazoles in all three tautomeric forms. The method selectively gives access to various 2-substituted 2H-indazoles which are frequently used in drug design, and we also demonstrated its applicability to less studied 3H-indazoles.

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.

Tandem C-N Coupling/Boulton-Katritzky Rearrangement Reactions of 3-Aminoisoxazoles or 1,2,4-Oxadiazol-3-amines with 2-Pyridyl Trifluoromethanesulfonate: A Rapid Access to [1,2,4]Triazolo[1,5-a]pyridines

An efficient and convenient synthesis of functionalized [1,2,4]triazolo[1,5-a]pyridines derivates is presented. The protocol is through a palladium catalyzed tandem C-N coupling/Boulton-Katritzky rearrangement process from 3-aminoisoxazoles or 1,2,4-oxadiazol-3-amines with 2-pyridyl trifluoromethanesulfonate....

Access and modulation of substituted 1-methyl-1,6-dihydropyrazolo[3,4-c]pyrazoles

Despite the pharmacological potential of the pyrazolo[3,4-c]pyrazoles, only a few methods of preparation and direct functionalization of this moiety have been described. We report herein a convenient design of new pyrazolo[3,4-c]pyrazoles with a high therapeutic impact. The effective chosen strategy consists of hydrazine condensations and C–N Ullmann-type cross-coupling reactions with microwave activation. Moreover, chemoselective bromination of the newly formed bipyrazoles followed by Suzuki–Miyaura cross-coupling reactions allowed the synthesis of a variety of modulated heterobicycles.

A convenient design of pyrazolo[3,4-c]pyrazoles is reported through hydrazine condensations and C–N Ullmann-type cross-coupling reactions. Chemoselective bromination followed by Suzuki–Miyaura cross-coupling reactions access to a variety of modulated heterobicycles.

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

A stereospecific synthesis of ( E)-5-tetrasubstituted-ylidene-3,5-dihydro-4 H-imidazol-4-one derivatives is demonstrated through a cascade process by combination of a Michael addition and Boulton-Katritzky rearrangement. The method provides a simple and efficient approach for the synthesis of ( E)-5-tetrasubstituted-ylidene-3,5-dihydro-4 H-imidazol-4-ones from the reactions of N-(isoxazol-3-yl)-propiolamides or N-(1,2,4-oxadiazo-3-yl) propiolamides with N or C nucleophiles.