Electrophilic cyclizations of α,β-alkynic hydrazones by molecular iodine were investigated for the synthesis of 4-iodopyrazoles. α,β-Alkynic hydrazones were readily prepared by the reactions of hydrazines with propargyl aldehydes and ketones. When treated with molecular iodine in the presence of sodium bicarbonate, α,β-alkynic hydrazones underwent electrophilic cyclization to afford 4-iodopyrazoles in good to high yields. Iodocyclization was general for a wide range of α,β-alkynic hydrazones and tolerated the presence of aliphatic, aromatic, heteroaromatic, and ferrocenyl moieties with electron-withdrawing and electron-donating substituents.

An efficient and general method for the synthesis of 1,4‐oxazepines is described. When reacted with ZnCl2 in DCM at 40 °C or CHCl3 at 61 °C, N‐propargylic β‐enaminones undergo 7‐exo‐dig cyclization to afford 2‐methylene‐2,3‐dihydro‐1,4‐oxazepines in good to high yields. This cyclization has been found to be general for a diverse range of N‐propargylic β‐enaminones, and proceeds with high efficiency and with broad functional group tolerance. The reactions in refluxing CHCl3 produced 1,4‐oxazepines in comparatively short reaction times and with better yields that those obtained in refluxing DCM. This operationally easy method may provide rapid access to a library of functionalized 1,4‐oxazepine derivatives of pharmacological interest.

Synthesis of pyrazoles via electrophilic cyclization of α,β-alkynic hydrazones by copper(I) iodide is described. When treated with copper(I) iodide in the presence of triethylamine in refluxing acetonitrile, α,β-alkynic hydrazones, prepared readily from hydrazines and propargyl aldehydes and ketones, undergo electrophilic cyclization to afford pyrazole derivatives in good to excellent yields. The reaction appears to be general for a variety of α,β-alkynic hydrazones and tolerates the presence of aliphatic, aromatic, and ferrocenyl moieties with electron-withdrawing and electron-donating substituents.

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