General Information All purchased solvents and chemicals were of analytical grade and used without further purification. Melting points: Electrothermal-9100 apparatus. IR Spectra: Shimadzu-IR-460 spectrometer; ν max in cm-1. 1 Hand 13 C-NMR Spectra: Bruker DRX-500 Avance instrument using CDCl 3 as applied solvent and TMS as internal standard at 500.1 and 125.7 MHz, respectively.; δ in ppm, J in Hz. Mass spectra were recorded on a Finnigan-MAT-8430EI-MS mass spectrometer; at an ionization potential 70 eV; in m/z (rel. %). Elemental analyses for C, H, and N were performed using a Heraeus CHN-O-Rapid analyzer. General Procedure General procedures for the preparation of indolizine derivatives 5 and 11: A mixture of quinaldine (0.286 g, 2 mmol), pyridine or isoquinoline (4 mmol) and I 2 (0.506 g, 2 mmol) in MeCN (4 mL) was warmed to 60 °C for 2 h. (i-Pr) 2 NEt (0.541 g, 4.2 mmol) and a solution of 1 (2 mmol) in MeCN (1 mL) were then added. The resulting mixture was left at 60 °C overnight. Then, kept in a freezer for 24 h. The precipitate was filtered,

Alkyl 2-(3-alkyl-4-oxo-2-thioxothiazolidin-5-ylidene)acetates react with hydrazonoyl chlorides in the presence of triethylamine to ­afford tetrasubstituted pyrazole derivatives. Formally, this transformation is regarded as a 1,3-dipolar cycloaddition of the exocyclic carbon–carbon double bond of the thioxothiazolidine derivatives with nitrile imines generated in situ. This efficient method provides fast access to a range of structurally diverse pyrazoles. The structure of a typical product is confirmed by X-ray crystallography.

An efficient transition-metal-free approach toward C-H bond activation by using molecular [Formula: see text]-mediated [Formula: see text] C-H bond functionalization for the synthesis of indolizine derivatives via 1,3-dipolar cycloaddition reaction of nitrogen ylides with ynones is described.

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A novel synthesis of spirocyclopropane‐1,4′‐pyrazolin‐5′‐one derivatives via iodine‐mediated C(sp3)–H activation is described. Thus, a diastereoselective synthesis of spirocyclopropane‐linked pyrazolones from 4‐arylidene‐3‐methyl‐1‐phenylpyrazolin‐5‐ones and azomethine ylides, generated in situ from iodine‐catalyzed reaction of 2‐methylquinoline or acetophenones with pyridine in the presence of base, has been developed. These transformations proceeded via a cyclopropanation reaction followed by anti‐elimination of pyridine. Unequivocal evidence for the structures of spirocycles rac‐anti‐5 a and rac‐anti‐12 a were obtained from single‐crystal X‐ray analyses. These methods offer several advantages, such as being inexpensive, moderate to high yield, high atom economy, and ease of product isolation, which make them attractive processes for the synthesis of spirocyclopropane‐linked pyrazolones. The spirans reported in this work may deserve further attention not only from a synthetic but also from a pharmacological point of view.