1.3- Diphenylisobenzofurane

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). 

Reduction of isoindoles with dissolving metals or catalytically occurs in the pyrrole ring. Reduction of indolizine with hydrogen and a platinum catalyst gives an octahydro derivative. With a palladium catalyst in neutral solution, reduction occurs in the pyridine ring but in the presence of acid, reduction occurs in the five-membered ring (Scheme 38). Reductive metallation of 1,3-diphenylisobenzofuran results in stereoselective formation of the cw-1,3-dihydro derivative (Scheme 39) (80JOC3982). 

Diphenylisobenzofuran has been reported to react with azirine (75) in refluxing toluene to give cycloadduct (81), the primary product of a [4 + 2] cycloaddition (72JOC2508, 74JOC2031). ... 

Diphenylisobenzofuran [5471-63-6] M 270.3, m 129-130°. Recrystd from EtOH or EtOH/CHCl3 (1 1) under red light (as in photographic dark rooms) or from benzene in the dark. 

Cava and Schlessinger have reported the synthesis of 1,2,3-triphenyl-isoindole (65) in 78% yield from 1,3-diphenylisobenzofuran (68) hy reaction with thionylaniline (69) and boron trifluoride. The mechanism proposed for this remarkable transformation involves reaiTangement of the adduct (70) derived from thionylaniline and the isobenzofuran, to the tricyclic intermediate (71). This presumably collapses to the S-sultam (72), which yields the isoindole (65) upon extrusion of sulfur dioxide. Loss of sulfur dioxide, both from S-sultones and unsaturated S-sultams, is well documented. ... 

Mercury-sensitized irradiation of 1,2,3-triphenylisoindole (65) in the presence of oxygen gives a peroxide (103). This peroxide is relatively stable compared with the peroxide (104) derived from similar oxidation of 1,3-diphenylisobenzofuran and can be reconverted to the isoindole (65) by pyrolysis or by treatment with zinc and acetic acid. Reduction of 103 under mild conditions affords o-dibenzoylbenzene (46) and aniline. Aerial oxidation of 47 gives 46 and methylamine, presumably via a peroxide intermediate similar to 103. °... 

Ethyl 1/7-azepine-l-carboxylate (1) yields the [2 + 4] enc/o-cycloadducts 16 with isobenzofuran (15, R = H) and with 1,3-diphenylisobenzofuran (15. R = Ph).251 l-Mesyl-lZ/-azepine behaves likewise. 

Based on the high dienophilicity of acyclic vinyl sulfones one should expect thiete dioxides to exhibit similar properties. Indeed, several Diels-Alder (2 +4) cycloadditions with thiete dioxide as dienophile are known. For example, 1,3-butadiene and 1,3-diphenylisobenzofuran react with 3-chloro- or 3-bromo-thiete dioxides to afford the corresponding 1 1 Diels-Alder cycloadducts255 277 (equation 105). 

Another strained alkylidenecyclopropane, 2-methylbicyclo[3.1.0]hex-l-ene (21), formed by cyclization of the carbenoid generated from dibromide 20 at 0 °C gave, in the presence of an excess of 1,3-diphenylisobenzofuran (10), a very small amount (5%) of a 2 1 mixture of diastereoisomeric Diels-Alder adducts 22 (Scheme 4) [11a]. The parent furan does not capture 21 even when used as solvent for the carbenoid cyclization. 

T. Ohyashiki, M. Nunomura, and T. Katoh, Detection of superoxide anion radical in phospholipid liposomal membrane by fluorescence quenching method using 1,3-diphenylisobenzofuran. Biochim. Biophys. Acta. 1421, 131-139 (1999). 

On converting 1-benzothiophene into 1-phenyl-1-benzothiophenium triflate (95), this salt becomes a dienophile and reacts readily with cyclopentadiene or 1,3-diphenylisobenzofuran to give the adduct 96 (Scheme 45).143 This example of the dienophilic nature of the double bond in the benzothiophene ring arises from reduced aromaticity. 

Scheme 6.14 Trapping of 6 with 1,3-diphenylisobenzofuran (DPIBF) and proof ofthe chirality of6 by formation of non-racemic products 50.

Scheme 6.90 Products of the reactions ofthe cyclic allene 417 with furan, 1,3-diphenylisobenzofuran and pyrrole.

Scheme 6.108 Products ofthe interception of 1,2,4,6-cyclohepta-tetraene (5) with 1,3-diphenylisobenzofuran, anthracenes, 2,5-dimethyl-3,4-diphenylcyclopenta-2,4-dien-l-one, methyl 2-pyrone-5-carboxylate, tropones, 8,8-dicyanoheptafulvene and 1,3,5-cycloheptatrienes.

Dimers with a 1,2-bismethylenecyclobutane structure were obtained from 585 [240], 590 [238], 591 [241], 592 [242], 593 [243] and from the pinene derivative 597 [244]. The interception of 592 by 1,3-diphenylisobenzofuran (DPIBF) afforded two diastereomeric [4+ 2]-cycloadducts [245], Bicyclo[5.1.0]octa-3,4-diene (594) was generated by /3-elimination and trapped by sodium pyrrolidide because of the question of the extent to which the corresponding bicyclooctyne is formed in addition to 594 [184], Liberated by /3-elimination from ll,ll-dichloro-l,6-methano[10]annulene in... 

Diphenylisobenzofuran (DPIBF, 44) or furan have been used to intercept cyclopropa[fl]naphthalene (56) and cyclopropa[/]phenanthrene (142). ° ° DPIBF (44) reacts with 1 in THF at 20 °C to form exo and endo adducts 321 and 322 217 unsymmetrical adduct 323, resulting from ring-opening of 1, may also be obtained if the reaction is carried out in CHCl, in particular at higher temperatures." " ... 

The strain of the triple bonds of 5 could also be reflected by its chemical reactivity with furan, 1,3-diphenylisobenzofuran, as well as dichloroketene (Scheme 3). Mention should be made of my first use of furans in a Diels-Alder reaction, because this first encounter has sparked my enduring interest in furan chemistry throughout my research career (Section 6). 

In practice, bromination of 35 gave the tetrabromide 37, which was dehydro-brominated carefully to the dibromide 38. Further dehydrobromination with an excess of KO-r-Bu furnished only a mixture of 40 and 42. It was likely that the dehydrobromination pathway was of a stepwise manner, going through 39 and 41 as intermediates (Scheme 9), although none of which could be trapped. The presence of 39 and 41 was indirectly proved by the isolation of an adduct 43 through a dehydrobromination of 38 in the presence of 1,3-diphenylisobenzofuran." It was quite clear that the instabilities of 39 and 41 were also due to the severe pen-H-H interaction, as indicated in 44. 

There are photocalorimetric enthalpy data for two other ozonides, both coming from sensitized photochemical dioxygenation reactions in non-polar solvents . This study reports the enthalpies of the reactions of 2,5-dimethylfuran and 1,3-diphenylisobenzofuran to their corresponding endoperoxides to be exothermic by —45 20 and —92 25 kJmoU (the latter value is an average of the values given for different solvents). From... 

Since the seminal work of Bartlett [363] there have been relatively few reports of useful cycloadditions of fluoroalkenes. Recent work by Haufe showed that fluorine atom substituents depress the reactivity of styrene derivatives in the Diels-Alder reaction with 1,3-diphenylisobenzofuran. A single fluorine atom in the /1-position lowered the rate of the [4 + 2] reaction by a factor of ten when the fluorine atom occupied the -position (Eq. 142), the reaction was over 30 times slower than that of the unsubstituted styrene. 

---