A Novel Reaction of the “Huisgen Zwitterion” with Chalcones and Dienones: An Efficient Strategy for the Synthesis of Pyrazoline and Pyrazolopyridazine Derivatives

Abstract

Two unexpected transformations: The reaction of the Huisgen zwitterion derived from triphenylphosphane and diisopropyl azodicarboxylate (DIAD) with chalcones affords functionalized pyrazolines. In contrast, the reaction with dienones affords pyrazolopyridazines, presumably by Diels–Alder reaction of the initially formed pyrazoline with excess DIAD (see scheme).

Reactions of Morita-Baylis-Hillman Acetates with Huisgen Zwitterions: A Novel Strategy for the Synthesis of β-Amino Acid Derivatives

“…2 In view of our longstanding interest in zwitterion chemistry, 3 recently we have explored the reactivity of Huisgen zwitterion towards various substrates like aldehydes, ketones, chalcones, diaryl 1,2-diones, quinones, isatins, and allenes. [4][5][6] In this context it was of interest to examine the reactivity of Huisgen zwitterion towards Morita-Baylis-Hillman (MBH) adducts, 7,8 which are unique substrates of great synthetic potential incorporating three manipulatable groups, namely, a hydroxy group, a double bond, and an electron-withdrawing group. In this paper, we describe the results of our investigations on the reaction of Huisgen zwitterion with MBH acetates.…”

Scaffold Diversity Synthesis Delivers Complex, Structurally, and Functionally Distinct Tetracyclic Benzopyrones

“…A reaction of chalcones ( 1 ) with Huisgen's zwitterion ( I ) was reported to form pyrazolines 5 [Eq. (1), Scheme ] . In the reaction, the zwitterionic dipole ( I ) reacted with a ketone functional group to form an intermediary iminium dipole ( 4 ), which cyclizes to form a pyrazoline ring.…”

A regioselective Synthesis of Substituted Pyrazolines via a Cascade Annulation of Huisgen Zwitterion with α‐Cyano‐α,β‐unsaturated Ketones Under Solvent‐free Heating Conditions

“…The Huisgen zwitterion could react with carbonyl compounds to afford various products . For example, Nair and co‐workers used this zwitterion to synthesize N , N ‐dicarboethoxy monohydrazones, dihydro‐1,2,3‐benzoxadiazoles, and functionalized pyrazole, pyrazoline, as well as pyrazolopyridazine derivatives (Scheme , a) . Very recently, we introduced a cascade aza‐Michael/Aldol annulation of Huisgen zwitterions with 2‐arylidene indane‐1,3‐diones for the construction of indeno‐pyrazolines (Scheme , b) .…”