2.5- Diphenyl-3,4-isobenzofurane

Numerous examples of unstable bridgehead olefins trapped by dienes such as 2,5-diphenyl-3,4-isobenzofuran, furan, and similar compounds have been reported (96). However, systematic studies for probing the reactive double bond and strain effects are rare. 

When an attempt was made to produce rrcm.v-cycloheptene from trans-1,2-cycio-heptenethionocarbonate (8) by the same procedure, only cfy-cycloheptene was obtained. However, the reaction of trans-1,2-cycloheptenethionocarbonate (8) with trimethyl phosphite in the presence of 2,5-diphenyl-3,4-isobenzofurane (9) as trapping agent gave an adduct (10), m.p. 150°, isomeric with the known adduct of the benzofurane with cii-cycloheptene, m.p. 185°. It is apparent, therefore, that trans-cycloheptene is the primary product from trans- 1,2-cyclohcptenethionocarbonate. 

With only five methylene units available to bridge the tmns double bond, the molecule is highly strained and very reactive. Isolation of. E-cycloheptene has not been possible, but evidence for its formation has been obtained by trapping experiments. The alkene is generated in the presence of a reagent expected to react rapidly with it— in this case, the very reactive Diels-Alder diene 2,5-diphenyl-3,4-isobenzofuran. The adduct that is isolated has the structure and stereochemistry anticipated for that derived from E-cycloheptene. The lifetime of -cycloheptene has been measured after generation by photoisomerization of the Z-isomer. The activation energy for isomerization to Z-cycloheptene is about 17 kcal/mol. The lifetime in pentane is on the order of minutes at... 

Enantiomeric (E)-cyclooctene (20E) was first resolved in 1963 through its diastereomeric platinum(II) complex. Synthesis of optically active 20E has been the subject of intensive study since 1968. The first preparation involves the treatment of enantiopure (E)-cyclooctane-l,2-thiocarbonate with triisooctyl phosphate or of (E)-cyclooatane-l,2-trithiocarbonate with l,3-dibenzyl-2-methyl-l,3,2-diazaphospholi-dine. Following analogous synthetic routes, enantiomeric (E)-cycloheptene (18E) can be produced and trapped by 2,5-diphenyl-3,4-isobenzofuran as an optically active adduct. In 1973, the circular dichroism spectrum of enantiopure 20E vapor was recorded in the vacuum UV region down to 150 nm. The first enantiodifferentiating Z-E photoisomerization of cyclooctene sensitized by chiral benzenecarboxylates appeared in 1978. Transfer of chiral information from sensitizer to substrate occurs within the exciplex intermediate. ... 

Photolysis of 1,4-diphenylphthalazine 2-oxide in various solvents gives 1,3-diphenyl-isobenzofuran (52) as the primary product. In the presence of oxygen, deoxygenation to 1,4-diphenylphthalazine and oxidation of the initially formed 1,3-diphenylisobenzofuran (52) to 1,2-dibenzoylbenzene also take place (Scheme 17). 

Dimethyl anthracene and diphenyl isobenzofuran form remarkably stable233 cyclopropanone derivatives (353/354), whilst with other diene components (butadiene, tetracyclone, and fulvene) the primarily formed Diels-Alder adducts either suffer ketalizing attack of the solvent (356 - 357, 359 - 358/360) or undergo irreversible changes such as decarbonylation to 362 or rearrangement to 355. 

Another example of a diene with extra ordinarily high reactivity is diphenyl benzo (c) furan (diphenyl isobenzofuran)... 

The interesting tricyclic compound 55 49), which has ( )-cycloheptene moiety, was found to be very labile and could only be trapped by condensing with diphenyl-isobenzofuran. 

Recently, the bicyclic cyclopropanones 78 and 79 were prepared in high yield by the Diels-Alder addition of cyclopropenone to the diphenyl-isobenzofuran 80 and the dimethylanthracene 57.62>... 

In order to confirm the stmcture of the tricyclic thietane 60, it underwent several reactions <20040L1313>, which were performed on the substituent of the ring carbon atom. The thietane 60 underwent hydrogenation on palladium-on-charcoal to give the fully saturated compound 61. The presence of a double bond in compound 60 was also confirmed by [4+2] Diels-Alder cycloaddition of dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate as well as of diphenyl-isobenzofuran, which led to the formation of cycloadducts 62 and 63, respectively (Scheme 10) <20040L1313>. 

Azirine 91 has also heen shown to undergo a Diels-Alder reaction with diphenyl isobenzofuran to provide 94. The exo-isomct was reported to isomerize to the endo-isorac,i 95 upon heating, although no yields for this transformation were reported <2001J(P1)2969>. 

Benzyne trapping agents 2,5-Di-p-anisyl-3,4-diphenylcyclopentadienone. 1,3-Diphenyl-isobenzofurane. Tetraphylcyclopentadienone. 

Bicyclo[3.2.0]hept-l-ene (151) can be prepared from the tosylhydrazone of norbornan-7-one via norbornan-7-ylidene 150 in 74% as a stable olefin (144). Similarly, 152 has been obtained from norborn-2-en-7-one in a yield of 67% (144a). Introduction of a further double bond leads to the strained triene 153, which has been prepared from 105b (Scheme 3). Compound 153 dimerizes readily at room temperature to a 1 1 mixture of hydrocarbons 154 (145). The most likely structures of these dimers arise from a formal [2 + 2]cycloaddition of the bridgehead double bonds of 153 with each other. Support for the intermediacy of 153 comes from trapping experiments with 1,3-diphenyl-isobenzofuran, which yield a mixture of stereoisomers via reaction with the bridgehead double bond of 153. 

The role of exciplexes in self-sensitized photo-oxidations has been further investigated by Stevens and co-workers.273 - Photoperoxidation of 1,3-diphenyl-isobenzofuran in solution proceeds at a rate which is independent of acceptor concentration when this is very low, and this observation has been interpreted in terms of a re-encounter of x02 and ground-state acceptor molecules generated in the same triplet-triplet annihilation act. This interpretation accounts for the failure of tetramethylethylene to inhibit the reaction completely. Processes 1—3 in Scheme 8 account for the observations if re-encounter effects are included,... 

I>iphenylbenzo[c]thiophene, yellow needles, mp 118°C, is thermally stable. Its solution displays a green fluorescence. The compound can be prepared by ring transformation of 1,3-diphenyl-isobenzofuran with P4S10 in CS2. 

Aryne intermediates generated from the ortho-(trimethylsilyl)triphenylenyl tri-flate 127 have been found to undergo Diels-Alder cycloaddition with 1,3-diphenyl-isobenzofuran (128) upon treatment with TBAF, affording the polycyclic products 129 (Equation 12.36) [73]. 

Treatment of the dichloride (127) with methyl-lithium in presence of diphenyl-isobenzofuran (DPIBF) led to formation of (128), the structure of which was established by X-ray crystal diffraction. ... 

When irradiated through pyrex with a large excess of cycloheptatriene, 1,3-diphenyl-isobenzofuran gave a mixture of endo-and exo-[6 + 4] and-[4 + 4] adducts. Thermolysis gave only the cndo-[4 -f- 2]andexo-[6 4- 4] adducts. Photolytic cycloaddition... 

Attaching of fluorescent probes to PLP has also been used to determine PLP. Chauhan and Dakshinamurti employed reductive amination of PLP with methyl anthranilate and sodium cyanoborohydride to form a highly fluorescent amine (83). Durko et al. (54) prepared diphenyl-isobenzofurane derivatives of Be vitamers to enable fluorometric measurement of vitamin Be. However, the use of fluorescent probes are generally not suitable for routine analytical work, mainly because the unreacted fluorescent probe may interfere in Be vitamer quantification (83). 

Strong chemiluminescence was observed only in dimethylphthalate as solvent. Small quantities of water enhanced the light yield but oxygen had no distinct influence on the chemiluminescence [24 a]. Phthaloyl peroxide exhibits chemiluminescence with a series of other fluorescent compounds such as BPEA, pyrene, perylene, 1,3-diphenyl isobenzofuran, and fluorescein. 

Strong quenching effects were observed by 02,1,3-pentadiene, tri-t-butyl phenol and tetramethylethylene (in increasing order of effectiveness). As DP A and 1,3-diphenyl isobenzofuran act as fluorescers, but not 9,10-dibromoan-thracene, the active species appears to be in the singlet state, although quantitative results have not been reported. It was concluded from the kinetic and spectroscopic data that dioxetanedione as well as the 1,4-diradical are present not only in the... 

In this case, an o-xylylene peroxide is formed, confirmed by the isolation of the Diels-Alder adduct (53) with maleic anhydride in 70% yield, and by infrared spectroscopy. If the peroxide (52) is heated to ca. 100°, o-dibenzoylbenzene is formed in 85% yield, together with ca. 5% of 1,3-diphenyl isobenzofuran (54) and 2% phenyl o-benzoyl benzoate (55). 

Diphenyl cyclopropenone has been reacted with activated dienes like diphenyl isobenzofuran234 and diethylamino butadiene194. Interestingly, the isobenzofuran does not add to the CVC2 bond as in cyclopropenone, but to the C /C3 bond in a (3+4) cycloaddition as indicated by the product 363. 

Diels-Alder cycloadditions involving thiete sulfones as dienophiles occur with butadiene,cyclopentadiene, 1,2,3,4-tetraphenylcyclopentadiene, anthracene. tetraphenylcyclopentadienone, l,3-diphenyl-2H-cyclopenta[l]-phen-anthrene-2-one, a-pyrone, l-(Af,Af-dimethyl)- and l-(7V,A -diethyl)-l,3-butadiene, furan, 2,5-dimethylfuran, l,3-diphenylisobenzofuran, isobenzofuran," and l,3-diphenylnaphtho[2,3-c]furan. Generally, thiete... 

Diels-Alder dienes 1-Acetoxybutadiene. Butadiene. Cyclopentadiene. (rans,mins-l,4-Diacetoxybutadiene. 2,5-Di-o-anisyl-3,4-diphenylcyclopentadienone. 5,5-Dimethoxy-l, 2,3,4-tetrachlorocyclopentadienone. 2,3-Dimethylbutadiene. 6,6-Dimethylfulvene (see o-Acetoxy acrylonitrile). 2,4-Dimethyl-l,3-pentadiene (see Diethyl azodicarboxylate). 2,3-Diphenyl-butadiene. 1,3-Diphenylisobenzofurane (see Potassium I-butoxide). rrans,/nus-l,4-Diphenyl-butadiene. 1,3-Diphenylisobenzofurane. Hexachlorocyclopentadiene. Isobenzofurane. l-o-Nitrophenylbutadiene-1,3. Oxepin (see Diazabicyclo[3.4.0]nonene-S). Phenylcyclone. Piperylene. n-Pyrone (see also Methyl vinyl ketone). Tetrachlorocyclopentadienone. Tetra-chlorofurane. Tetraphenylcyclopentadienone. 

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