Photochemical processes of benzyltrimethylsilane at 77 K remarkable solvent effects and reaction mechanism

Hiratsuka, Hiroshi; Kadokura, Yukihiro; Chida, Hiroyuki; Tanaka, Miéko; Kobayashi, Satoshi; Okutsu, Tetsuo; Oba, Makoto; Nishiyama, Kozaburo

doi:10.1039/ft9969203035

Cited by 15 publications

(21 citation statements)

References 13 publications

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“…In view of the reaction sequence proposed above, this is not unreasonable, since the ArÀOZ cleavage has to confront a high barrier in this case (Figure 4) and this opens the path to homolytic desilylation to yield radical 14. [21] In summary, this work greatly enlarges the scope of our initial report on chlorobenzylsilanes and clarifies the range of possibilities for photochemical access to DHTs. Thus, aryl sulfonates and, albeit with a lower efficiency, phosphates can be used in place of halides for the photochemical generation of DHTs via phenyl cation intermediates (path a in Scheme 3).…”

Section: Scheme 2 Products Obtained Upon Irradiation Of Aryl Esters 1-3mentioning

confidence: 57%

Competing Pathways in the Photogeneration of Didehydrotoluenes from (Trimethylsilylmethyl)aryl Sulfonates and Phosphates

Crespi¹,

Ravelli²,

Protti³

et al. 2014

Chemistry A European J

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The scope of the photochemical generation of α,n-didehydrotoluene diradicals from aryl sulfonates and phosphates and their chemistry are explored. The thermally inaccessible α,2- and α,4- intermediates are efficiently obtained by irradiation of ortho- and para-(trimethylsilylmethyl)phenyl triflates through heterolytic splitting of the ester anion from the substrate in the triplet state. Triplet phenyl cations are formed and the loss of trimethylsilyl cation from them affords the desired diradicals ((3) Me3 SiCH2 C6 H4 -OZ→(3) Me3 SiCH2 C6 H4 (+) →(⋅) CH2 C6 H4 (⋅)). Triplet sensitization is required, for which acetone is used throughout. Direct irradiation leads, on the contrary, to photo-Fries fragmentation ((1) Me3 SiCH2 C6 H4 O-Z→Me3 SiCH2 C6 H4 O(⋅) +Z(⋅)). With mesylates, where ester cleavage is less convenient, a further competition from the triplet is direct desilylation. Didehydrotoluenes are also obtained from the corresponding phosphates, although with poor efficiency.

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Section: Scheme 2 Products Obtained Upon Irradiation Of Aryl Esters 1-3mentioning

confidence: 57%

Competing Pathways in the Photogeneration of Didehydrotoluenes from (Trimethylsilylmethyl)aryl Sulfonates and Phosphates

Crespi¹,

Ravelli²,

Protti³

et al. 2014

Chemistry A European J

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“…Benzyltrimethylsilane (3) was first reported to be inert to photolysis in solution (20), but Kira et al (19) later found that extended photolysis of the compound in hydrocarbon solution leads to the inefficient formation of ortho-tolyltrimethylsilane (18a), which they suggested to arise from a minor reaction of benzyl and trimethylsilyl radicals produced by homolysis of the benzyl carbon-silicon bond in the benzylsilane. More recently, spectroscopic evidence for the formation of free benzyl radicals upon photolysis of 3 in an ethanol matrix at 77 K has been reported by Hiratsuka et al (29).…”

Section: Resultsmentioning

confidence: 93%

“…1 H, 13 C, and 29 Si NMR spectra were recorded using Bruker AC200, Bruker AC300, or DRX500 NMR spectrometers. Infrared spectra were recorded on a BioRad FTS-40 FT/IR spectrometer and are reported in wavenumbers (cm -1 ).…”

Section: Methodsmentioning

confidence: 99%

The one- and two-photon photochemistry of benzylsilacyclobutanes, acyclic benzylsilanes, and 1,1,2-triphenylsilacyclobutane

Leigh¹,

Owens²

2000

Can. J. Chem.

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The photochemistry of several α-silylbenzyl compounds has been investigated in hexane and in methanol solution. Direct photolysis of 1-benzyl-1-methylsilacyclobutane (1) in methanolic hexane solution produces 1-propyl-1-methyl-2,3-benzosilacyclobutene (6) in quantitative yield, by a sequential two-photon process involving the photoactive isotoluene derivative 1-methylene-6-(1-methylsilacyclobutyl)-2,4-cyclohexadiene (13a), which has been identified on the basis of its 1H NMR and UV absorption spectra. In contrast, direct irradiation of 1-benzyl-1-phenylsilacyclobutane (2) under similar conditions results in the formation of a complex mixture of products consistent with the competing formation of 1-benzyl-1-phenylsilene and benzyl- and 1-phenylsilacyclobutyl radicals. The silene is a transient which has been detected directly by laser flash photolysis of 2 (λmax = 315 nm, τ ~ 4.5 µs). Free radical formation is shown to be due to secondary photolysis of a second primary product, 1-methylene-6-(1-phenylsilacyclobutyl)-2,4-cyclohexadiene (13b), which has also been detected and identified by static UV absorption (λmax = 335 nm) and 1H NMR spectroscopy. In a reaction with some analogy to the acid-catalyzed desilylation of allylsilanes, both 13a and 13b can be intercepted in neutral or acidic methanol solution to yield toluene and 1-methyl- or 1-phenyl-1-methoxysilacyclobutane, respectively. Direct photolysis of benzyldimethylphenylsilane (4) also leads to the formation of the corresponding isotoluene derivative, while benzyltrimethylsilane (3) exhibits negligible photoreactivity. The endocyclic benzylsilane 1,1,2-triphenylsilacyclobutane (5) is shown to undergo competing [2 + 2]-cycloreversion and [1,3]-silyl migration to yield a bicyclic isotoluene analogue, which reacts rapidly with methanol to yield the acyclic methoxysilane reported previously to be the main product of photolysis of this silacyclobutane in methanol solution. Relative quantum yields for isotoluene formation from photolysis of 1-4 and absolute rate constants for methanolysis of several of these compounds under neutral and acidic conditions have also been determined.Key words: photochemistry, organosilicon, benzylsilane, silacyclobutane, silene, kinetics, isotoluene.

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“…4 times stronger than that of 1a, which was intramolecularly quenched by the trimethylsilyl group. 5 In addition, the monomer fluorescence intensity of 1a-d at 290 nm decreased with increase of the number of benzyl groups, accompanying an increase of the excimer fluorescence at 345 nm (Figure 1).…”

mentioning

confidence: 95%

“…4 Very recently, Hiratsuka et al have clarified the photophysical and photochemical processes of 1a at 77 K and the molecular structure of its excited state by MNDO-PM3 calculations. 5 However, little is known about the synthesis and photochemical behaviour of 2,2'-silaspirobiindan and its related group 14 element compounds, 6 although spiro conjugated compounds having two perpendicular π-electron systems have been widely investigated. [7][8][9] We now report the synthesis and photochemical behaviour of 2,2'-sila-and germa-spiro compounds and their related compounds.The benzyl-substituted silanes (1a-d) and the spirocompounds 2a-c were prepared by the Grignard method or the literature method (see Scheme 1).…”

mentioning

confidence: 99%

Synthesis and photochemical properties of 2,2′-silaspirobiindan and related compounds

Inoue

Sugimoto

Mizuno

2000

Journal of Chemical Research

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In the last three decades, much attention has been focused on the photochemical reactions of group 14 element compounds because of their characteristic properties and reactivities. [1][2][3] Kira and Sakurai have previously reported the photorearrangement of benzyltrimethylsilane (1a) and (acyloxy)methyl-substituted benzylsilanes via C-Si photo-cleavage. 4 Very recently, Hiratsuka et al. have clarified the photophysical and photochemical processes of 1a at 77 K and the molecular structure of its excited state by MNDO-PM3 calculations. 5 However, little is known about the synthesis and photochemical behaviour of 2,2'-silaspirobiindan and its related group 14 element compounds, 6 although spiro conjugated compounds having two perpendicular π-electron systems have been widely investigated. [7][8][9] We now report the synthesis and photochemical behaviour of 2,2'-sila-and germa-spiro compounds and their related compounds.The benzyl-substituted silanes (1a-d) and the spirocompounds 2a-c were prepared by the Grignard method or the literature method (see Scheme 1). 6,10 For example, 2,2'-silaspirobiindan 2b was obtained by treatment of the Grignard reagent of o-xylylenedichloride with tetrachlorosilane in THF in a 52 % isolated yield. 11 The product was purified by flash column chromatography on silica gel using hexane eluent and repeated recrystallisation from methanol. Similarly the related group 14 element compounds were synthesised in good yields. The results are summarised in Table 1.

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Photochemical processes of benzyltrimethylsilane at 77 K remarkable solvent effects and reaction mechanism

Cited by 15 publications

References 13 publications

Competing Pathways in the Photogeneration of Didehydrotoluenes from (Trimethylsilylmethyl)aryl Sulfonates and Phosphates

Competing Pathways in the Photogeneration of Didehydrotoluenes from (Trimethylsilylmethyl)aryl Sulfonates and Phosphates

The one- and two-photon photochemistry of benzylsilacyclobutanes, acyclic benzylsilanes, and 1,1,2-triphenylsilacyclobutane

Synthesis and photochemical properties of 2,2′-silaspirobiindan and related compounds

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