A novel photosubstitution of dicyanobenzenes by allylic and benzylic silanes

Mizuno, Kazuhiko; Ikeda, M.; Otsuji, Yoshio

doi:10.1016/s0040-4039(00)61911-1

Cited by 90 publications

(10 citation statements)

References 10 publications

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“…In all of the above cases, the generated radical anion (A–Y •− ) is a persistent species easily detected by laser flash photolysis. This approach applies to a variety of donors, including amines [12–13], carboxylic acids or their derivatives [14–15], aliphatic acetals and ketals [16], ethers [17], organostannanes [18–19], organosilanes [20–22], aromatics [10,23–24], and even alkanes [25–27]. BET (path a') could ensue, thus leading to no chemical change.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

Fagnoni¹,

Protti²,

Ravelli³

et al. 2013

Beilstein J. Org. Chem.

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SummarySteady-state irradiation in neat acetonitrile of some aromatic nitriles, imides and esters (10−5–10−3 M solution) in the presence of tertiary amines allowed the accumulation of the corresponding radical anions, up to quantitative yield for polysubstituted benzenes and partially with naphthalene and anthracene derivatives. The condition for such an accumulation was that the donor radical cation underwent further evolution that precluded back electron transfer and any chemical reaction with the radical anion. In fact, no accumulation occurred with 1,4-diazabicyclo[2.2.2]octane (DABCO), for which this condition is not possible. The radical anions were produced from benzene polyesters too, but decomposition began early. Ipso substitution was one of the paths with secondary amines and the only reaction with tetrabutylstannane. The results fully support the previously proposed mechanism for electron transfer (ET) mediated photochemical alkylation of aromatic acceptors via radical ions and radical intermediates.

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Section: Introductionmentioning

confidence: 99%

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

Fagnoni¹,

Protti²,

Ravelli³

et al. 2013

Beilstein J. Org. Chem.

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“…In the absence of authentic samples, the structures of the products were assigned by comparison with reported spectral data as in the cases of 31, 32…”

Section: Structural Assignmentsmentioning

confidence: 99%

Photochemical reactivity of α‐phenyl β,γ‐enones. Singlet 1,3‐acyl shift, triplet aromatic di‐π‐methane (DPM) rearrangement and triplet aryl‐carbonyl bridging

Koppes

Beentjes

Cerfontain

1988

Recl. Trav. Chim. Pays‐Bas

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Abstract. The photochemistry of the series of a-phenyl P,y-enones 6-10 has been studied under conditions of both direct (A 300 nm) and triplet-sensitized irradiation with the aim of determining the reactivity patterns of these "mu1ti"-chromophoric systems. Upon direct irradiation, the reactants exhibit the typical photoreactions of P,y-enones, viz. the 1,3-acyl shift, affording the corresponding (E)-and (Z)-5-phenyl-4-hexen-3-ones, decarbonylation of the radicals formed by a-cleavage and recombination of the resulting alkyl radicals and, in addition, a new type of reaction from the triplet-excited state yielding small amounts of the corresponding acetophenones. The acetophenones are thought to be formed by initial P-bridging between the carbonyl and the phenyl group, followed by extrusion of the C,H, fragment from the 1,4-or 1,3-0xa-diradical. Upon sensitized irradiation, the o-methoxy-and p-cyano-substituted reactants 9 and 10 exhibit the di-n-methane rearrangement, leading to mixtures of the corresponding cis-and trans-1 -acetyl--1 -methyl-2-phenylcyclopropanes, with quantum yields of 0.03 and 0.10, respectively. The formation of the 1,3-AS and decarbonylation products illustrates the occurrence of a-cleavage, whereas the acetophenones and di-n-methane products are formed via initial aryl-carbonyl and aryl-vinyl bridging, respectively. The inability of the other a-phenyl P,y-enones to undergo photocyclopropanation is discussed in terms of excitation-energy partition. In the o-methoxy-and p-cyano-substituted reactants, the excitation energy may be predominantly concentrated in the aryl moiety in contrast to the other two systems in which the excitation energy may be mainly localized on the P,y-enone moiety. Subsequent triplet-energy dissipation by a free-rotor mechanism would then account for the stability of these systems. This was observed for (E)-7 which, upon triplet sensitization, affords only the (Z) isomer, whereas this process is degenerate for the other substrates studied.

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“…This mechanistic proposal was consistent with the finding that photoaddition of the prenylsilanes 9b and 9c to pyrrolinium salt 10b lead to generation of the same adduct 10b, demonstrating that the same allyl radical intermediate 13b was involved in both processes. At nearly the same time, the group headed by Mizuno [5,6] observed that allylsilanes participate in photoaddition reactions with electron-deficient cyano-arenes and -alkenes. One example arising from their earlier work is photoaddition of trimethylallysilane 9a to 1,4-dicyanobenzene (14), which produces adduct 15 via pathway where initial SET generates the ion radical pair 16 ?…”

Section: Introductionmentioning

confidence: 98%

“…Benzylsilanes were also observed to participate as electron donors in photoinduced SET reaction pathways [5,9,10]. As with those derived from allylsilanes, benzylsilane cation radicals undergo nucleophile-promoted desilylation in processes that generate benzyl radicals.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, shortly after that time, several research groups initiated efforts to discover new photochemical reactions that are driven by excited state SET with the hope that these processes would add to the growing repertoire of reactions that could be used to prepare organic substances. In the early 1980s, independently and nearly simultaneously groups headed by Mizuno [5,6] and Mariano [7,8] recognized that SET-promoted photochemical reactions, in which allyl and benzyl silanes participate as electron donors, might serve as both efficient and useful preparative methods. Both groups reasoned that in these processes, SET from the silicon-containing substrates 5 (Scheme 2) to excited state acceptors would be facilitated by the presence of electropositive trialkylsilyl groups that stabilize the forming cation radical intermediates 6.…”

Section: Introductionmentioning

confidence: 99%

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A strategy for the preparation of cyclic polyarenes based on single electron transfer-promoted photocyclization reactions

et al. 2011

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Single electron transfer (SET)-promoted photocyclization reactions of substrates comprised of benzylsilane tethered to phthalimides were subjected to an exploratory study in order to probe a new approach for the preparation of cyclic polyarenes. The results show that UV irradiation of the substrates leads to efficient photochemical reactions that are initiated by SET from benzylsilane moieties to the excited phthalimide acceptor. Ensuing desilylation reactions of the benzylsilane cation radical moieties in the intermediate zwitterionic biradicals and proton transfer gives biradical precursors of the cyclic polyarene products. The observations made in this effort suggests that SET photochemical methods, which have been employed earlier to generate cyclic poly-ethers, -thioethers and -amides, serve as a useful method to access potentially interesting macrocyclic targets.

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A novel photosubstitution of dicyanobenzenes by allylic and benzylic silanes

Cited by 90 publications

References 10 publications

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

Photochemical reactivity of α‐phenyl β,γ‐enones. Singlet 1,3‐acyl shift, triplet aromatic di‐π‐methane (DPM) rearrangement and triplet aryl‐carbonyl bridging

A strategy for the preparation of cyclic polyarenes based on single electron transfer-promoted photocyclization reactions

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