Heterocyclic mesomeric betaines

http://pubs.acs.org/doi/pdf/10.1021/ol503338b

N-Aminopyridinium Salts as Precursors for N-Centered Radicals – Direct Amidation of Arenes and Heteroarenes

Azomethine imines are considered 1,3-dipoles of the aza-allyl type which are transient intermediates and should be generated in situ but can also be stable and isolable compounds. They react with electron-rich and electron-poor olefins as well as with acetylenic compounds and allenoates mainly by a [3 + 2] cycloaddition but they can also take part in [3 + 3], [4 + 3], [3 + 2 + 2] and [5 + 3] with different dipolarophiles. These 1,3-dipolar cycloadditions (1,3-DC) can be performed not only under thermal or microwave conditions but also using metallo- and organocatalytic systems. In recent years enantiocatalyzed 1,3-dipolar cycloadditions have been extensively considered and applied to the synthesis of a great variety of dinitrogenated heterocycles with biological activity. Acyclic azomethine imines derived from mono and disubstituted hydrazones could be generated by prototropy under heating or by using Lewis or Bronsted acids to give, after [3 + 2] cycloadditions, pyrazolidines and pyrazolines. Cyclic azomethine imines, incorporating a C–N bond in a ring, such as isoquinolinium imides are the most widely used dipoles in normal and inverse-electron demand 1,3-DC allowing the synthesis of tetrahydro-, dihydro- and unsaturated pyrazolo[1,5-a]isoquinolines in racemic and enantioenriched forms with interesting biological activity. Pyridinium and quinolinium imides give the corresponding pyrazolopyridines and indazolo[3,2-a]isoquinolines, respectively. In the case of cyclic azomethine imines with an N–N bond incorporated into a ring, N-alkylidene-3-oxo-pyrazolidinium ylides are the most popular stable and isolated dipoles able to form dinitrogen-fused saturated and unsaturated pyrazolopyrazolones as racemic or enantiomerically enriched compounds present in many pharmaceuticals, agrochemicals and other useful chemicals.

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1,3-Dipolar cycloadditions of azomethine imines

This invention is directed to an m x n array of different chemical compounds wherein each of said compounds has at least one structural diversity element selected from a group of amines and ketones and wherein the scaffold structure is selected from a group consisting of aminimide, imidazolone, sulfonylaminimide and phosphonylaminimide.

A method of generating a plurality of chemical compounds in a spatially arranged array

Publisher Summary This chapter describes the reactions of acetylenecarboxylic esters with nitrogen-containing heterocycles Some reactions of dimethyl acetylenedicarboxylate (DMAD), the corresponding diethyl ester (DEAD), methyl (MP) and ethyl propiolates (EP), and ethyl phenylpropiolate (EPP) take place with reasonable certainty through each of radical, ionic, and concerted pathways Reactions between nitrogen-containing heterocycles and acetylenic esters often lead to complex mixtures, which may require chromatography and great experimental skill for successful resolution The products sometimes depend on the precise conditions employed, and on the purity of the reactants or solvents The choice of solvent can be important Thus, ether and tetrahydrofuran give different results for the combination of DMAD with 1-methylbenzotriazole The products obtainable from indoles and quinazolines are particularly dependent on the reaction conditions and purity of the solvent The chapter discusses compounds from six-membered ring heterocycles containing only nitrogen as heteroatom, five-membered rings containing only nitrogen as heteroatom, four-membered ring nitrogen-containing heterocycles, and three-membered ring nitrogen-containing heterocycles

Roland Krischke

Papers

1.3-additionen mit pyridin-imin, chinolin-imin, isochinolin-imin und phenanthridin-imin

1,3‐Dipolare Cycloadditionen, 84. Additionen mit Chinolinium‐, Isochinolinium‐ und Phenanthridinium‐N‐imid2)

1,3‐Dipolare Cycloadditionen, 83. Pyridinium‐N‐imid als additionsbereites Azomethinimin