Rapid and selective synthesis of spiropyrazolines and pyrazolylphthalides employing Seyferth–Gilbert reagent

Abstract

An unexpected product-selectivity in the reaction of 2-arylideneindane-1,3-dione with dimethyl diazomethylphosphonate leading to the formation of two different types of products is reported. The reaction carried out in acetone in the presence of catalytic amount of cesium fluoride afforded spiropyrazoline phosphonates via 1,3-dipolar cycloaddition reaction, whereas the reaction in methanol yielded an interesting class of pyrazolylphthalides. This strategy provides an efficient alternative method for the construction of pyrazolylphthalides, and moreover, the process is general, works under mild conditions, and exhibits high functional group compatibility.

The Bestmann‐Ohira Reagent and Related Diazo Compounds for the Synthesis of Azaheterocycles

“…2020, 20, 1394 -1408 pyrazolineindane-1,3-dione 15 was obtained in modest yields using catalytic amount of CsF in acetone. [22] Henceforth, the scope and limitations of the spiropyrazoline synthesis were evaluated (Scheme 9). Interestingly, substrates bearing electron-releasing and electron-withdrawing substituents at the para-position of the phenyl ring, efficiently transformed into the anticipated products (15 a-15 h).…”

“…We realized our hypothesis by reacting 2‐arylideneindane‐1,3‐dione 14 with a stoichiometric amount of Seyferth‐Gilbert reagent 1 , under those previously reported conditions for the synthesis of pyrazoles. Gratifyingly, the corresponding spiropyrazolineindane‐1,3‐dione 15 was obtained in modest yields using catalytic amount of CsF in acetone [22] …”

Indane-1,3-Dione: From Synthetic Strategies to Applications

“…Seyferth-Gilbert reagent 468 is a reagent classically used to transform carbonyl groups into alkynes. Such a reactant was notably used in association with indanedione derivatives 255 to form spiropyrazolineindane-1,3-diones 458 using CsF as the base [307]. When the 2-arylidene-indane-1,3-diones 255 and the Seyferth-Gilbert reagent 468 were mixed with sodium hydroxide, 3-pyrazolylphthalide 470 could be obtained.…”

Stereoselective Synthesis of Tri- and Tetrasubstituted Olefins via 1,6-Additions of Diazo Compounds and Their Precursors to p-Quinone Methides

“…Yet another class of compounds of continued interest are diazo compounds, which are precursors to carbenoids and, therefore, are employed in various reactions such as insertion, cyclopropanation, ring expansion, etc. to construct a multitude of cyclic and acyclic organic frameworks. , The utility of diazo compounds such as α-diazo-β-ketophosphonate (Bestmann–Ohira reagent) and its corresponding sulfone and ester analogues as 1,3-dipole precursors has been demonstrated in base-mediated deacylative [3 + 2] cycloaddition with conjugated electron-deficient alkenes for the synthesis of various functionalized heterocycles. − These reactions are largely based on 1,4-additions of the diazo compounds followed by cyclization in an overall [3 + 2] annulation. However, the corresponding deacylative 1,6-additions remained unexplored.…”