DMF‐Catalyzed Direct and Regioselective C–H Functionalization: Electrophilic/Nucleophilic 4‐Halogenation of 3‐Oxypyr­azoles

Abstract

A novel, straightforward, and highly regioselective 4-chlorination of 3-oxypyrazole derivatives in boiling thionyl chloride (SOCl 2 ) in the presence of catalytic N,N-dimethylformamide (DMF) has been developed. This reaction likely proceeds through a DMF-catalyzed electrophilic/nucleophilic chlorination mechanism and involves electrophilic attack by

N,N‐Dimethylformamide: A Multipurpose Building Block

“…[1] Furthermore, it can also participate in reactions as a dehydrating agent, [2] as a source for a reducing agents, [3] or even as a catalyst. [4] More importantly, because of its structure, DMF can participate in many reactions by serving as a multipurpose building block for various units, such as O, -CO, -NMe 2 , -CONMe 2 , -Me, -CHO, etc. (Scheme 1).…”

Ethyl 2-{[5-(3-chlorophenyl)-1-phenyl-1H-pyrazol-3-yl]oxy}acetate

“…The title compound was prepared by the literature method (Liu et al, 2011). Crystals suitable for X-ray analysis were obtained by dissolving I (0.5 g) in ethyl acetate (25 ml) and evaporating the solvent slowly at room temperature for about 10 d.…”

A Convenient One-Pot Synthesis of 1-Aryl-Substituted 4-Iodopyrazol-3-Ols via Aromatisation and Oxidative Iodination Reactions

“…15 Existing methods (Scheme 1) for the synthesis of 4-iodopyrazol-3-ols have the following one or more drawbacks: (1) many by-products, which results in lower yields and difficult separation of products; (2) use of large quantities of FeCl 3 , leading to large amounts of iron waste; (3) problems of atom economy, which are not ideal for large-scale production. 16,17 Here we report a facile one-pot, metal-free and iodine-atomeconomic synthetic protocol for the preparation of a series of new 4-iodopyrazole-3-ols from inexpensive and easily available pyrazolidin-3-ones using only 2 equiv. of H 2 O 2 , 1 equiv.…”