Iron(III) Chloride/Diorganyl Diselenides: A Tool for Intramolecular Cyclization of Alkynone O-Methyloximes

Abstract

This report describes the synthesis of 4-organoselenylisoxazoles via FeCl(3)/RSeSeR-mediated intramolecular cyclization of alkynone O-methyloximes. The optimized conditions allowed the cyclization to proceed at room temperature under ambient atmosphere, and the reaction requires a short time to be completed. The reaction conditions tolerated neutral, electron-donating and electron-withdrawing groups present in both substrates, alkynone O-methyloximes and diorganyl diselenides. Treatment of 4-organoselenylisoxazoles with n-butyllithium, followed by trapping with electrophiles, furnished the functionalized isoxazoles in good yields. The obtained products also proved to be suitable substrates for the preparation of 4-bromoisoxazoles via Br/Se exchange reaction.

Synthesis of Seleno‐Heterocycles via Electrophilic/Radical Cyclization of Alkyne Containing Heteroatoms

“…The optimized conditions allowed the cyclization to proceed at room temperature under ambient atmos- phere, and the reaction requires a short time to be completed (Scheme 17). [45]…”

Three-Component Reactions of Alkynone o-Methyloximes, Element Selenium, and Boronic Acids Leading to 4-Organoselenylisoxazoles

“…A representative and conventional synthetic method 12 for 4-organoselenylisoxazoles relied on the FeCl 3 -promoted reactions of alkynone o -methyloximes and diorganyl diselenides, but it suffered from low-to-moderate yields (no more than 70%) and required the use of stoichiometric FeCl 3 ( Scheme 1 c).…”

Iron(III) Chloride/Diorganyl Diselenides Promoted Regio‐ and Stereoselective Cyclization of ortho‐Alkynylanilides: Synthesis of (Z)‐4‐(chalcogen)methylenebenzoxazines

“…Recently, a mixture of FeCl 3 /PhSeSePh was found to be an alternative system to promote the cyclization of unsaturated substrates 11. More recently, we have also demonstrated FeCl 3 /PhSeSePh as an efficient system for the preparation of vinyl selenides,12 organoselenoisoxazoles,13 organoselenoisochromenones14 and organoselenochromenones 15. The cyclization of ortho ‐alkynylanilides is an appropriate way to produce nitrogen heterocycles, such as indoles and benzoxazines 16.…”