1.3- Diphenylisobenzofuran 2+4 cycloadduct with

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 cycloadducts (equation 105). 

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). ... 

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. 

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... 

Density functional theory computational studies have been used to determine die importance of secondary orbital interactions for the stability of transition-state structures for die 4 + 2-cycloaddition of furan with cyclopropene.175 Kinetic studies of die 2 + 4-cycloaddition of 2-cyclopropylidene acetates with furan and dimethylful-vene suggest a mechanism involving diradicals or zwitterions as intermediates.176 Cyclopropene, produced by die reaction of allyl chloride with sodium bis(bimediyl-silyl)amide, reacts with 1,3-diphenylisobenzofuran to produce both endo- and exo-Diels-Alder cycloadducts isolated for the first tune.177... 

The author indicated that in a 1989 Kodak Research Technical Report, with the exception of the diphenylisobenzofuran, dienes used in the Diels-Adler reaction with epoxybutene failed to generate the indicated cycloadducts of the current invention (1). 

Diphenylisobenzofuran also reacted with cyclopropa[a]naphthalene to give an adduct 9 of unknown stereochemistry in ca. 40% yield however, cycloadducts of cyclopropa[Z ]naph-thalene have not as yet been described. Cyclopropa[/]phenanthrene underwent cycloaddition with furan to give the endo-aAAuci 10 (28%) and its evo-isomer 11 (17%). ... 

Alkylidenecycloproparenes react in cycloadditions either with the exocyclic double bond, or with the bridging 7t-bond, When l-(diphenylmethylene)benzocyclopropene reacted with 1,3-diphenylisobenzofuran, a crystalline 1 1 euofo-cycloadduct 20 was produced, which resulted from reaction with the central 7i-bond. ° In contrast, cycloaddition of l-(diphenylmethyl-ene)cyclopropa[Z)]naphthalene to 1,3-diphenylisobenzofuran proceeded via attack at the exocyclic double bond and resulted, ultimately, in a l-(diphenylmethylene)cyclobuta[i]naph-thalene derivative 21. ° ... 

Compound 232 gave exo cycloadducts, along with smaller amount of the endo isomer in reaction with both dienes. Reactions of 233 with diphenylisobenzofuran led exclusively to the exo-isomers, in contrast to the endo diastereoselectivity observed for nonfluorinated a,p-unsaturated carbonyl compounds. 

The intramolecular Diels-Alder cycloadditions of 1-aminobenzofurans provide a simple synthesis of benzo[/r]quinolines. A-Acetyl-2-azetine undergoes facile 4-1-2-cycloaddition with cyclopentadiene, 5,5-dimethoxy-1,2,3,4-tetrachlorocyclopentadiene, hexachloropentadiene, and diphenylisobenzofuran to produce exclusively endo-cyc o-adducts. The highly strained cyclic alkyne bicyclo[2.2.1]hept-2-en-5-yne (108), prepared from the heptavalent iodine precursor (107), has been trapped using 1,3-diphenylisobenzofuran to yield the adduct (109) (Scheme 41). The reaction of sodium dinitroxytrioxide (110) with 1,3-diphenylisobenzofuran gives an initial 4-1-2-cycloadduct (111), which rearranges to the final product (112) (Scheme 42). " The... 

The six-membered ring strained butatriene 36 is also trapped with diphenylisobenzofuran to give the [4+2] cycloadduct 37 in 29 % yield... 

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