Access to 5,5'-diaryl substituted 4,5,4',5'-tetrahydro[3,3']bi-isoxazolyl 2,2'-dioxides, 4,5,4',5'-tetrahydro[3,3']bi-isoxazolyls and [3,3']bi-isoxazolyls via an initial ring-opening of 3,4-dinitrothiophene

Abstract

By means of an iodide-catalyzed nitrocyclopropane to 4,5-dihydroisoxazoline 2-oxide isomerization, the 1,1′-dinitro-[1,1′]bi(cyclopropyl)s 5, deriving from an initial ring-opening of 3,4-dinitrothiophene 1, can be stereospecifically converted into the bisnitronates 6. From these, successive N-oxide reduction [P(OMe) 3 /dioxane] and aromatization (DDQ/toluene) provide convenient access to the interesting 4,5,4′5′-tetrahydro[3,3′]bi-isoxazolyls 7, and [3,3′]biisoxazolyls 8, respectively.

A Click Chemistry Approach to 5,5′-Disubstituted-3,3′-Bisisoxazoles from Dichloroglyoxime and Alkynes: Luminescent Organometallic Iridium and Rhenium Bisisoxazole Complexes

“…The brown−yellow solids were analyzed by electrospray mass spectrometry and signals for the monocations were the major peaks in the observed in the spectrum each with the expected isotope patterns: m/z 789. 1844 13 C and 1 H NMR spectra of these diamagnetic low-spin d 6 complexes were as expected. In complex 11 coordination to Ir(III) results in a downfield shift in the resonance attributed to the proton of the isoxazole ring when compared to the "free" ligand 5 (this resonance is at δ 7.09 ppm in 5 and shifts to δ 8.26 ppm in complex 11).…”

“…32 mp 198−199. 1 H NMR (500 MHz, d 6 -DMSO) δ 13.1 (s, 2H); 13 C NMR (125 MHz, (CD 3 ) 2 SO) δ 130.7.…”

“…3,3′-Bisisoxazoles have been assembled in a complex multistep sequence from bis-nitrocyclopropanes, 13 or in two steps by dipolar cycloaddition of the bis-nitrile oxide dicyanide-N-oxide and silylenol ethers, followed by aromatization. 14 The most direct route to 3,3′-bisisoxazoles is by 1,3-dipolar cycloaddition of dicyanide-N-oxide with 2 molecules of alkyne.…”

Boronate Urea Activation of Nitrocyclopropane Carboxylates

“…Under these optimized conditions we were unable to observe any successful ring-opening of nitrocyclopropanes with primary amines, such as benzyl amine. It is noteworthy to mention that the rearrangement of 4 to the corresponding isoxazoline N -oxide, a problem encountered under many types of Lewis acidic conditions (BF 3 OEt 2 , AlCl 3 , and others), was not observed in any reaction catalyzed by a urea. , …”

A Mild Procedure for the Lewis Acid-Catalyzed Ring-Opening of Activated Cyclopropanes with Amine Nucleophiles

“…However, the generation of acyclic products via strictly nucleophilic processes almost invariably requires elevated temperatures and/or basic conditions, with the exception of organometallic reagents . Such vigorous reaction conditions can lead to various undesired side reactions, such as an intramolecular rearrangement of the cyclopropane. ,– , …”