trans-1,2-Disiloxybenzocyclobutene, an adequate partner for the auto-oxidation: EPR/spin trapping and theoretical studies

Abstract

The auto-oxidation of trans-1,2-disiloxybenzocyclobutene was found to be very efficient, giving endo-peroxide in quantitative yield. Each step of the mechanism of spin-forbidden addition of triplet oxygen O2((3)Σg) was studied by both EPR/spin trapping and theoretical studies.

Capturing the Organic Species Derived from the C–C Cleavage and in Situ Oxidation of 1,2,3,4-Tetra(pyridin-4-yl)cyclobutane by [CuCN]n-Based MOFs

“…In this transformation, the cyclobutane ring of tpcb underwent only one C−C bond cleavage, which was different from the cleavage of the cyclobutane ring into two olefins. 30 Where did the O atom of tpyf in 2 originate from? Under the N 2 atmosphere, the similar reaction of the same components could not afford 2.…”

“…The [2 + 2] photodimerization of olefins and the cycloreversion of the resulting cyclobutane species via UV/microwave irradiation or UV/heating have been reported and might be applicable in switching devices and rewritable optical data storage. − However, the mechanism of the cyclobutane cycloreversion has remained arguable . Although many techniques like in situ NMR, mass spectroscopy, and electron paramagnetic resonance (EPR) could be available for the mechanism investigation, − it is still a tough job to acquire important information about the in situ formed intermediates, which are key to understanding the mechanism of organic reactions. Recently, metal–organic-frameworks (MOFs) have become one type of powerful structural materials which can be used as straightforward alternative tools for performing some organic reactions and capturing the in situ cleaved species within their frameworks. − We also reported that the hydrothermal reaction of CdCl 2 with 1,3-benzene­dicarbox­ylic acid (1,3-H 2 bdc), 1,3-bis­(4′-pyridyl)­2,4-bis­(phenyl)­cyclobutane (HT-ppcb), and H 2 O 2 afforded one unique 2D MOF, {[Cd­(H 2 O)­(1,3-bdc)­(bpbpf)]·H 2 O} n (bpbpf = 2,4-bis­(4-pyridyl)-3,5-bis­(phenyl)­furan) .…”

On the ring-opening of substituted cyclobutene to benzocyclobutene: analysis of π delocalization, hyperconjugation, and ring strain

“…Thus, we focus on the thermodynamics of the opening reaction, since the reaction barrier of the opening process was crossed under experimental conditions. 18 A spin-catalysis like mechanism could be at work here and lower the opening barrier. 19 Our discussion is based on DH R values, defined as follows:…”

“…Recently, it has been proven that the transdisiloxybenzocyclobutene combines easily with dioxygen in its triplet state. 18 This opens up the perspective of new, stable molecules capable of catching radical systems. In our previous work, it has been shown that the open form combines easily with dioxygen in its triplet state.…”

Theoretical Studies of Autoxidation of 2-Alkylidene-1,3-cyclohexadione Leading to Bicyclic-Hemiketal Endoperoxides

“…3 Previous studies have shown the implication of fundamental oxygen in its triplet state 3 ∑ – g – O 2 and have discarded the alternative of a radical reaction. 4 This spin-forbidden reaction constitutes the key step to prepare endoperoxides with antimalarial properties and an alternative green process. To elucidate the mechanism of this intriguing reaction, a precedent electron paramagnetic resonance (EPR)/spin-trapping study combined with mass spectroscopy has been undertaken, using two spin traps and starting from the precursors labeled with 13 C in different positions.…”