Photolysis of a Benzyne Precursor Studied by Time-Resolved FTIR Spectroscopy

Abstract

The 266 nm laser flash photolysis of phtaloyl peroxide (2) in liquid acetonitrile solution at room temperature has been investigated. Upon 266 nm laser irradiation, 2 is effectively photodecarboxylated leading to the formation of o-benzyne (1) and two equivalents of CO2, yet a small fraction of photolyzed 2 follows a different pathway leading to 6-oxocyclohexa-2,4-dienylideneketene (3) and one equivalent of CO2. Compound 3 is kinetically reactive and reacts in the microsecond time scale following a first-order kinetic law. The presence of 1 in the photolysis experiment is confirmed by trapping experiments with methyl 1-methylpyrrole-2-carboxylate (6). The Diels-Alder reaction between 1 and 6 occurs under the selected experimental conditions on a time scale shorter than 100 ms.

Computational NMR Spectra of o‐Benzyne and Stable Guests and Their Hemicarceplexes

“…According to the dimensions of the guest and cavity of the host, the o ‐benzyne has space to move inside the host molecule and a static optimized geometry may not be enough to obtain accurate chemical shift values. Note also that the results can be complicated by the fact that o ‐benzyne can react with an aromatic ring of its hemicarcerand host . For this reason, we examined the addition product of a Diels–Alder (DA) reaction between the o ‐benzyne and hemicarcerand 1 .…”

“…Note also that the resultsc an be complicated by the fact that o-benzyne can react with an aromatic ring of its hemicarcerand host. [45,[57][58][59][60][61] For this reason, we examined the addition product of aD iels-Alder (DA) reaction between the o-benzyne and hemicarcerand 1. o-Benzyne adds to one of the aryl ether units of 1 (diene component) to give the germinal para adduct (see Figure S4 in the Supporting Information). In the 1 HNMR spectrum of the 1@o-benzyne DA adduct, the protons ignals originating from o-benzynew ere identified at 6.14 (H a ), 5.21 (H b ), 4.58 (H c ), and 3.12 ppm (H d ).…”

“…Moreover,t he (de)complexation processes are controlled by ap rocess known as constrictive binding, whichi sr e-lated to the activationb arrierr equiredt ot rap the guest molecule inside the host cavity through as ize-restricting portal. [10] Several hemicarcerands have been synthesized by joining two cavitands with several linkers [3,6] and al arge varietyo fc ompounds have been incarcerated inside hemicarcerands cavities ranging from Xe [10] to large molecules such as ferrocene, adamantine, camphor, [11] or C 60 . [12] Hemicarcerands and otherc lasses of molecular containers can be used for many different applications in molecular recognition, catalysis, drug delivery,and storage.…”

All-SPEEK flexible supercapacitor exploiting laser-induced graphenization

“…An alternative route could be the formation of a carbon-carbon bond, and thus a benzyne, with elimination of sulfur dioxide and water as already demonstrated for aliphatic sulfonated [40]. In literature there are other cases in which irradiation of benzene precursors leads to production of benzyne [41,42]. This intermediate is instable and reacts really fast with nuclephiles such as phenols or directly with another benzyne to produce the bi-radical necessary for the graphenization (figure 3(d)).…”

Advances in the synthesis of nitrogen-containing heterocyclic compounds byin situbenzyne cycloaddition

“…91 Other non-commonly benzyne precursors have been reported in cyclization reaction applications. The photolysis of phtaloyl peroxide by laser flash at 266 nm can rapidly remove two CO 2 molecules to form benzyne, and N -containing compounds generated via the Diels–Alder reaction of the benzyne intermediate with 1-methylpyrrole-2-carboxylate (Scheme 21c) 92 The [4 + 2] cycloaddition reaction of the benzyne precursor (benzenediazonium-2-carboxylate) with azadiene is an effective strategy for the synthesis of aryl-substituted 1,4-dihydroquinolines. These products could be further oxidized to yield 4-arylquinolin-2-ones with biologically active and converted into aryl substituted quinoline compounds (Scheme 21d).…”