The biological and medicinal properties of 5-aminopyrazoles have prompted enormous research aimed at developing synthetic routes to these heterocyles. This review focuses on the biological properties associated with this system. Various synthetic methods developed up to 2010 for these compounds are described, particularly those that involve the reactions of β-ketonitriles, malononitrile, alkylidenemalononitriles and their derivatives with hydrazines, as well as some novel miscellaneous methods.

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-7-25.pdf

Approaches towards the synthesis of 5-aminopyrazoles.

New trends in the chemistry of 5‐aminopyrazoles

A new efficient procedure has been proposed for the synthesis of 3-aryl-5-amino-1H-pyrazoles by reaction of α-chloro-β-arylacrylonitriles with hydrazine hydrate.

New synthesis of 3-aryl-5-amino-1H-pyrazoles

A novel and efficient palladium and copper co-catalyzed intermolecular cyclization of acetonitriles with hydrazones has been developed for the synthesis of 5-aminopyrazoles through C-C and C N bond formation. The reaction has the advantages of easily available starting materials, simple manipulation and mild reaction conditions. The reaction involving various substituted acetonitriles and hydrazones proceeds smoothly and 5-aminopyrazoles are synthesized in good yields. In contrast to the aliphatic and heteroaromatic substrates, the aromatic substrates tend to have a higher degree of reactivity.

Palladium and Copper Cocatalyzed Intermolecular Cyclization Reaction: Synthesis of 5‐Aminopyrazole Derivatives

Publisher Summary This chapter provides information on six-membered ring systems with O and/or S atoms. The chapter discusses heterocycles containing one oxygen atom, including pyrans, benzopyrans (chromenes), dihydrobenzopyrans (chromans), pyranones, coumarins, chromones, flavonoids, xanthones, and pyrylium salts. The chapter discusses heterocycles containing one sulfur atom, including thiopyrans and analogues. The chapter also discusses heterocycles containing two or more oxygen atoms, including dioxins, and trioxins. The chapter also discusses heterocycles containing two or more sulfur atoms, including dithianes, and trithianes. Oxathiines are discussed under heterocycles containing both oxygen and sulfur in the same ring. The hetero-Diels-Alder (HDA) reaction involving aldehydes is catalyzed by Pd(II) complexes, such that even non-activated dienes give satisfactory yields of 5,6-dihydro-2Hpyrans. Chiral aluminium complexes are effective in controlling both the chemo- and enantio- selectivity of the reaction of alkyl glyoxylates with dienes containing an allylic C-H bond; high yields of the dihydropyran result with enantiomeric excesses of up to 97%. Stannyl derivatives of 2H-pyran-2-one, accessible from bromopyranones by cross coupling with organotin reagents, themselves take part in Pd(0)-catalyzed cross coupling with enol triflates. This methodology offers a new approach to steroidal pyran-2-ones.

Chapter 6.4 Six-membered ring systems: With O and/or S atoms

The preparation of N‐(1H‐pyrazol‐3‐yl)arylamides and 1H‐pyrazol‐3‐amines from polylithiated C(α),N‐thiosemicarbazones and C(α),N‐semicarbazones

The preparation of 4-oxo-N-aryl-4H-1-benzopyran-2-acetamides by the condensation/cyclization of trilithiated acetoacetanilides with lithiated methyl salicylates

Several acetoacetanilides were trilithiated in excess lithium diisopropylamide, and the resulting polylithiated intermediates were regioselectively condensed with lithiated methyl salicylates followed by acid cyclization to substituted 4-oxo-N-aryl-4H-1-benzopyran-2-acetamides (benzopyranone-2-acetamides).

The Preparation of 4-Oxo-N-aryl-4H-1-benzopyran-2-acetamides by the Condensation/Cyclization of Trilithiated Acetoacetanilides with Lithiated Methyl Salicylates.

Camille M. Kassis

Papers

The preparation of N‐(1H‐pyrazol‐3‐yl)arylamides and 1H‐pyrazol‐3‐amines from polylithiated C(α),N‐thiosemicarbazones and C(α),N‐semicarbazones

The preparation of 4-oxo-N-aryl-4H-1-benzopyran-2-acetamides by the condensation/cyclization of trilithiated acetoacetanilides with lithiated methyl salicylates

The Preparation of 4-Oxo-N-aryl-4H-1-benzopyran-2-acetamides by the Condensation/Cyclization of Trilithiated Acetoacetanilides with Lithiated Methyl Salicylates.