Search

Grignard reagents (R2MgBr; R2 = Me, p-tolyl) regioselectively attacked the α-carbon of the bridgehead double bond of methyl- and benzylazafulleroids (only R2 = Me) in contrast to the β-carbon attac...

Variously substituted [6,6]closed aziridinofullerenes were exclusively obtained from acid-catalyzed denitrogenation of triazolinofullerenes without formation of relevant [5,6]open azafulleroids, which are the major products on noncatalyzed denitrogenation. The mechanistic consideration by DFT calculations suggested a reaction sequence involving initial pre-equilibrium protonation of the triazoline N(1) atom, generation of aminofullerenyl cation by nitrogen-extrusion, and final aziridination.

CF3SO3H-catalyzed reaction of 5-alkyl-(R)-substituted diphenylhomobenzoquinone epoxides (R = Me, iPr, tBu) provided indenoquinones, a cyclopenta[b]chromene-2-carbaldehyde, and furan-3(2H)-ones through novel cationic domino rearrangements depending on the R substituents. The mechanisms of these reactions were described by a combination of various key steps involving (i) transannular cyclization of the endo-phenyl group, (ii) epoxide and cyclopropane ring opening, (iii) ring contraction of the original quinone frame, (iv) dehydration and intramolecular SE2/SN2-Ar cyclization, as well as (v) possible pseudopericyclic cheletropic decarbonylation.

A kinetic study of Diels–Alder (DA) reactions of some fullerene dienophiles, i.e. C60, [R1, R2]-substituted fulleroids 1 (a: [H, H], b: [H, CN], c: [H, CO2Et]; d: [H, Ph], e: [Ph, Ph]) and [H, H]-substituted methanofullerene (2), with various dienes [cyclopentadiene (3a), 9-methylanthracene (3b), 1,3-cyclohexadiene (3c), 2,3-dimethylbutadiene (3d) and 2-methylbutadiene (3e)] has been carried out in toluene at 30 °C. Notably, the relative rate ratio k/k0 for each dienophile (vs. C60) was remarkably dependent on the diene used; the less hindered H/CN fulleroids 1a and 1b became 25–104 times more reactive than C60 with conformationally flexible dienes such as 3d and 3e. These fulleroids, however, showed similar or rather diminished reactivity with rigid 3a and 3b. In contrast, slightly hindered 1c exhibited a three to seven times reduced rate of reaction for 3d–e, and more hindered 1d–e and the 58-π-conjugated 2 displayed reduced reactivity with almost all the dienes. Based on product analysis, the enhanced reactivity was ascribed to the exclusive addition at the highly strained bridgehead double bond of the transannular [5,6] open ring orifice. It was concluded that the twisted anti-Bredt double bond can perform a topologically suitable [π2s + π4s] orbital interaction with the less congested, labile dienes. Such an orbital interaction is inhibited for both the congested fulleroids and the rigid dienes, which displayed alternative addition at a less twisted double bond.

The AlCl3-catalyzed acetylation of 1,2-hydrophenylated [60]fullerenes, HC60-Ar, proceeded via a sequential manner involving the acetylation at the hydrogenated fullerene carbon, the following intramolecular cyclization with the adjacent aryl group, the facile loss of water, and the second acetylation of the generated indenylidene double bond. However, the similar reaction of the hydrobiphenylated analogue brought about the normal acetylation at the terminal aromatic ring prior to the same sequential reactions as did hydrophenylated fullerenes.

An irradiation of diphenylbicyclo[4.2.0]oct-3-ene-2,5-diones bearing variously substituted Me groups resulted in the reversible intramolecular [2+2] cycloaddition between the excited enedione C C double bond and the facing endo -phenyl ring to exclusively give pentacyclotetradeca-10,12-diene-2,7-diones. The equilibrated product ratios were much dependent on the substitution pattern of the Me-groups as well as the irradiated wavelength. The regiochemistry of these photoadditions was elucidated on the basis of the restricted conformation of the starting enediones.

[reactions: see text] We investigated the site selectivity switch in BF3-catalyzed dual skeletal rearrangements of cyclobutene-fused diarylhomobenzoquinones by changing the stoichiometric amount of acid concentration. From the lower to the higher equivalency of BF3 x Et2O, the branching product ratios (path A/path B) obeyed nonlinear sigmoid curves against the equivalency of BF3 x Et2O. The observed selectivity profiles were simulated to elucidate factors that govern thermodynamic aspects (binding affinity K of each carbonyl function with acid) and kinetic aspects (rate constants k for the cyclobutene-ring cleavage).

Lewis acid catalyzed rearrangements of highly strained [2 + 2] photoadducts 1a-d of diphenylhomobenzoquinone with various acetylenes were investigated under the influence of AlCl(3), SnCl(4), BF(3), and TiCl(4). With the relief of steric strain, these tricyclo[5.2.0.0(3,5)]non-8-ene-2,6-diones underwent the three steps of consecutive skeletal transformations. The first step was the two-way cyclobutene ring-cleavage reaction with a Wagner-Meerwein vinyl migration to either Lewis acid activated carbonyl function. This process virtually occurred under the anchimeric assistance of the endo-phenyl ring to give, after proton transfer, the phenylene-bridged tetracyclic keto alcohols 2 and 3, respectively. The next step was the acid-induced cyclopropane ring cleavage of only 3 to lead to bicyclic diones 4 via a following stereoselective proton transfer. The last one involved a Michael-type intramolecular cyclization of 4 accompanied by a proton transfer to afford thermodynamically less stable tricyclic diones 5alpha which epimerized to 5beta only by TiCl(4). The factors that control the selectivity and the reactivity of these tandem reactions were addressed on the basis of the X-ray crystal analyses as well as the PM3 calculations. It was found the present Lewis acid-catalyzed rearrangements were very dependent on the substituents of 1a-d and the nature of the Lewis acids.

When ‘thiocarbonyl ylide' 1A (=(2,2,4,4-tetramethyl-3-oxocyclobutylidenesulfonio)methanide) is generated from the dihydrothiadiazole 5A by N2 extrusion at 40° in the presence of 2,3-bis(trifluoromethyl)fumaronitrile ((E)-10), a cyclic seven-membered ketene imine 11 and trans-thiolane 12 are formed (81 : 19). The reaction of 1A with (Z)-10 furnishes 11, 12, and cis-thiolane 25 in the ratio of 82 : 12 : 6. The strained ketene imine 11 is crystalline and storable as a consequence of the stabilizing ‘perfluoroalkyl effect'. The ketene imine group is stereogenic; 11 has a transoid structure with respect to the CF3 groups, and there is no evidence for the cisoid diastereoisomer. Ketene imine 11 adds H2O, MeOH, and PhNH2. In solution at 60°, 11 undergoes an irreversible ring contraction, furnishing the thiolanes 12/25 98 : 2. The rate constant of this first-order rearrangement increases 850-fold, as the solvent polarity rises from cyclohexane to CD3CN, in accordance with a zwitterionic intermediate. It is the same intermediate that is initially formed from 1A and 10, and its intramolecular N- and C-alkylation give rise to 11 and 12+25, respectively. In contrast to 1A, thiocarbonyl ylide 27, which harbors the sterically less-demanding adamantylidene group, reacts with (E)-10 to give trans-thiolane 29, but no ketene imine. The precursor 26 catalyzes the (Z)/(E) isomerization of 10 ((E)/(Z) ca. 95 : 5 at equilibrium), thus obviating conclusions on steric course and mechanism of this cycloaddition.

Irradiation of a homobenzoquinone derivative with variously substituted alkenes and alkynes gave the [2 + 2] photocycloadducts, tricyclic diones, almost quantitatively as a mixture of regio- and stereoisomers. The preferred regioisomer for all reactions is attributed to the more stable 1,4-biradical intermediate (major addition mode), and the minor isomer is attributed to the less stable biradical (minor addition mode). A radical trapping experiment using benzeneselenol proved the generation of these two regioisomeric biradicals, reflecting the regioselectivity in selenol-free photoreaction. Both biradicals tended to preferentially yield the endo-isomer for the alkenes with smaller substituents such as ethoxy, cyano, and acetoxy groups, but the exo-isomer for the alkenes with larger substituents such as phenyl, carbazolyl, and tert-butyl groups. The logarithmic exo/endo ratios were well correlated with a combination of Taft's steric factor E(s) and the energy gain (DeltaE') associated with the orbital interactions between the spin centers of 1,4-biradicals. These results were interpreted in terms of Griesbeck's SOC mechanism as well as the possible bond rotation around the armed radical chain. Therefore, it is concluded that a balance of repulsive steric hindrance and the attractive FMO interaction determines the stereochemical course of the [2 + 2] photoaddition of homobenzoquinone derivative with variously substituted alkenes.

The tricyclic enedione, which was synthesized in the [2+2] photocycloaddition of homoquinone with alkyne, underwent a novel Lewis acid-mediated skeletal rearrangement to provide bi-, tri- and tetracyclic cage compounds, depending on the identity of the Lewis acid used. The prolonged reaction and the independent treatment of the intermediary products by other Lewis acids revealed that the reaction proceeds through successive, multi-step transformations involving a cyclobutene ring-cleavage, an intramolecular Friedel–Crafts addition, and a cyclopropane ring-opening as well as an intramolecular cyclization. The product distributions were governed by the identity of the Lewis acid and the coordinated carbonyl site.

Irradiation of various meta- and para-substituted homobenzoquinones with ethyl vinyl ether gave the [2 + 2] photoadducts, tricyclic diones, regio- and endo-selectively and in good yields. The tricyclic skeleton has an anti-form built by the addition of ethyl vinyl ether from the less hindered side of homoquinones. All of the CH3, Cl, Br, and CH3O substituents at the reacting CC double bond afforded head-to-head (HH) addition predominantly. In the case of CH3, Cl, and Br, the ethoxy group was oriented in the endo-position, while the CH3O substituent led to a 1/5 mixture with the exo-isomer. It was also found that the Br-substituted [2 + 2] adducts undergo a facile skeletal rearrangement, being converted into dihydro-o-benzoquinone monomethide derivatives for para-substitution and dihydrobenzofuran derivatives for meta-substitution, probably under the influence of the in situ generated HBr. Intramolecular [2 + 2] photocycloaddition of an alkenylhomobenzoquinone afforded a tetracyclic dione.

The kinetics of thermal cyclopropane ring-opening of a series of m- and p-substituted endo/exo diphenylbromohomonaphthoquinones 1a–i and the unsubstituted diphenylchlorohomonaphthoquinone 1j have been investigated and compared with biphenyl-2,2′-diylhalogenohomonaphthoquinones 2a,b. The first-order rate constants k/s−1 for 1a–i at 100 °C in toluene increased with the electron-donating ability of the substituents. The kinetic substituent effects were much more pronounced for the exo family than for the endo one and revealed the crucial role of the resonance contribution of diaryl groups; log (k/ko)exo = −1.99σ+ + 0.086 and log (k/ko)endo = −0.784σ+ + 0.002, respectively. The compounds 2a,b thermolyzed very quickly as compared with the corresponding diphenylhalogenohomonaphthoquinones 1e,j. The kinetic solvent effects on the thermolysis of representative compound 1e were so minute that the rates tended to slightly increase with the solvent polarity but decrease with the solvent basicity. These kinetic results were interpreted in terms of a concerted disrotatory ring opening of the incorporated cyclopropane ring.

1,3-Dipolar cycloaddition of 5-diazo-10,11-dihydro-5H-dibenzo[a,d]cycloheptene with 2,5-dimethyl-1,4-benzoquinone gave the less stable conformer of 10′,11′-dihydro-1,4-dimethylspiro[bicyclo[4.2.0]hept-3-ene-7,5′-(5′H-dibenzo[a,d]cycloheptene)]-2,5-dione (α-conformer) via a conformationally retained nitrogen extrusion from the sterically congested indazole adduct. X-Ray structure analyses revealed that the cycloheptene ring moieties adopt considerably strained twist-boat conformations in which the dihedral angles (θ) of the –CH2CH2– bridge are 77.1 and 27.3°, respectively. At 100 °C the α-conformer underwent a one-way conformational inversion to the more stable twist-boat conformer (β-conformer) with an almost gauche angle of θ = 55.5°. A kinetic study of the thermal inversion exhibited a small dependency on the quinone substituents as well as negligible solvent effects, providing the transition energy of 127 kJ mol–1. Semiempirical (PM3) calculations were performed to determine the optimized geometries of the α- and β-conformers as well as the inversion transition state structure, which were compared with the X-ray data.

Reactions of vinylcarbenoids with cyclic disulfides were carried out. Rh 2 (OAc) 4 -catalyzed reaction of vinyldiazo compounds 1a-c with biphenylene disulfide 6 gave 1,3-insertion adducts 7a-c as the sole products in very good yields, while the reaction with dithiaphenanthrene 9 afforded only 1,1-insertion adducts 10a-c .

The crystal structures of the two thermally equilibrated conformational isomers of the epoxide 1′,5′-dimethyl­spiro[10,11-dihydro-5H-dibenzo[a,d]cyclo­heptene-5,8′-4′-oxatricyclo[5.1.0.03,5]octane]-2′,6′-dione, C23H20O3, have been determined by X-ray diffraction. In the tricyclic dione skeleton, the oxirane and cyclo­propane rings adopt an anti structure with respect to the conjunct quinone frame. The spiro-linked 10,11-dihydro-5H-dibenzo[a,d]cyclo­heptene ring of the major isomer has a fairly twisted boat form, folding opposite to the adjoining cyclo­propane methyl substituent, whereas the seven-membered ring of the minor isomer has an almost ideal twist–boat form, inversely folding to the side of the relevant methyl group. The conformational structures of these isomers have been compared with those of the corresponding isomers of the unepoxidized homobenzoquinone.

The crystal structures of the two conformational isomers of the title compound, spiro[5,6-dihydro-11H-dibenzo[a,d]cycloheptene-1,11'-1a',2',7',7a'-tetrahydro-1H'-cyclopropa[b]naphthalene-2',7'-dione], C 25 H 17 BrO 2 , have been determined by X-ray diffraction. Isomer (I) has a conformation in which the spirodibenzocycloheptane moiety is close to the Br atom with a distance of 2.96 (3) A between the Br atom and the H atom at the 4-position of the tricyclic system. Isomer (II), obtained on heating (I), has a conformation in which the cycloheptane ring is flipped over apart from the Br atom and is characterized by the significantly short bibenzyl ethylene bond [1.458 (11) A]

A simple one-pot reaction using in situ chemically generated Na-naphthalenide as an electron reductant in the preferential generation of C(60)(2-) is described. Trapping of C(60)(2-) intermediate with 2 molar equiv of sterically hindered 2-bromo-2-methylmalonate ester afforded two singly bonded fullerenyl bisadducts C(60)[-CMe(CO(2)Et)(2)](2) in 35% and 7% yield, respectively. The regiochemistry of these two products was determined to be 1,4- and 1,16-bisadducts, respectively, by NMR, UV-vis-NIR, LCMS, and X-ray single crystal structural analysis. The minor 1,16-bisadduct 2 exhibits long wavelength absorption bands in the near-IR region and prominent electron-accepting characteristics as compared with those of the major 1,4-bisadduct and pristine C(60). As revealed by DFT calculation, we propose that the origin of these unusual characters of 2 arises from the moiety of [18pi]-trannulene, in close resemblance to that of the highly symmetrical emerald green 1,16,29,38,43,60-hexaadduct of C(60), EF-6MC(n). Accordingly, we anticipate a fast progressive formation of plausible 1,16-bisadduct-like intermediate moieties on a C(60) cage as the precursor structure leading to the formation of EF-6MC(n), by taking the corresponding regiochemistry and electronic properties into account.

Irradiation of a homobenzoquinone derivative with variously substituted alkenes and alkynes gave the [2 + 2] photocycloadducts, tricyclic diones, almost quantitatively as a mixture of regio- and stereoisomers. The preferred regioisomer for all reactions is attributed to the more stable 1,4-biradical intermediate (major addition mode), and the minor isomer is attributed to the less stable biradical (minor addition mode). A radical trapping experiment using benzeneselenol proved the generation of these two regioisomeric biradicals, reflecting the regioselectivity in selenol-free photoreaction. Both biradicals tended to preferentially yield the endo-isomer for the alkenes with smaller substituents such as ethoxy, cyano, and acetoxy groups, but the exo-isomer for the alkenes with larger substituents such as phenyl, carbazolyl, and tert-butyl groups. The logarithmic exo/endo ratios were well correlated with a combination of Taft's steric factor E(s) and the energy gain (DeltaE') associated with the orbital interactions between the spin centers of 1,4-biradicals. These results were interpreted in terms of Griesbeck's SOC mechanism as well as the possible bond rotation around the armed radical chain. Therefore, it is concluded that a balance of repulsive steric hindrance and the attractive FMO interaction determines the stereochemical course of the [2 + 2] photoaddition of homobenzoquinone derivative with variously substituted alkenes.

In the title compound, a diphenylhomonaphthoquinone, C 23 H 15 BrO 2 , the quinone frame adopts a slightly boat-shaped conformation, with folding angles of 11 (3) and 14 (3)°. The severe steric congestion between the endo-phenyl group and the quinone moiety results in considerable freezing of the aromatic ring.

The kinetics of the thermal rearrangement of a series of novel cyclopropyl-substituted [5,6] open fulleroids to the [6,6] closed methanofullerenes have been investigated in comparison with the aryl-substituted homologues. The cyclopropyl group markedly accelerated the rates due to the stereoelectronically favorable pi-conjugative effects in the radical-like [1,5] shift of the transient [5,6] closed isomers, overriding the geometrically constrained aryl group.

The substituent effects on diastereoselective formation of fulleroids in the reactions of C(60) with various unsymmetrical diazoalkanes were investigated. The steric demand on the stereochemical course of reactions dominated the diastereoselectivity for diazoalkanes bearing aliphatic as well as monosubstituted pi-resonating groups, whereas the stereoelectronic effects of coexisting pi-resonating aromatic and cyclopropyl groups played a crucial role in the ring closure of the radical intermediates, overriding the steric demand.

The X-ray structure analysis of the title compound, 2,5,8,11,14-pentaoxabicyclo[13.4.0]]nonadeca-15(1),17-diene-16,19-dione, C 14 H 18 O 7 , reveals that the fused quinone causes a significant deformation of the crown ring from the expected rectangular form, because of the serious steric repulsion between the two carbonyl groups and the two adjacent OCH 2 CH 2 units. One of these units deviates significantly from the mean plane of the quinone, while the other bends inward, remaining coplanar with the quinone. Such a constrained and folded structure is reflected in the abnormal sp 2 bond angles (110 and 130°) of one of the bridgehead quinonoid C atoms.

Bicyclic 3aH-cyclopentene[8]annulene-1,4-(5H,9aH)-diones underwent three types of acid-induced transannular reactions, Michael cyclization, [3 + 2] cycloaddition, and Friedel-Crafts ipso-alkylation, depending on the cyclopentenone ring substituent (Me or Ph) and the position of [8]annulenone substituent as well as the nature of acids (BF3, MeSO3H, CF3SO3H). The Me-substituent permitted the Michael reaction for all acids used to give tricyclic diones by the activation of cyclopentenone carbonyl group. However, the Ph-substituent inhibited the Michael reaction for BF3 and MeSO3H but allowed the [3 + 2] cycloaddition and Friedel-Crafts reaction for CF3SO3H depending on the position of annulenone substituent. These CF3SO3H reactions exhibited the following novel rearrangements, affording 2-naphthalenone and 7-acenaphthylene derivatives, respectively. The factors that control the reaction mode of these transannular cyclizations were discussed in view of the constraint twist-boat conformation of [8]annulenone ring as well as the ring substituent effects on the intramolecular cyclization. In addition, these [8]annulenone rings were found to easily undergo the intramolecular [2 + 2] photocyclization to provide the tetracyclic cage compounds which exhibited the facile cycloreversion under the influence of acid.

The structure of the title compound, C 21 H 20 O 2 , was determined by X-ray analysis. The results revealed that the 2,5-dioxocyclohexane skeleton is in a half-chair conformation, with torsion angles C(2)-C(1)-C(6)- C(5) -1.5 (3) and C(2)-C(3)-C(4)-C(5)-36.5(3)° on account of the fused cyclopropane ring which locates the 4-methyl group in an equatorial position. The plane of the endo-phenyl group was also found to be essentially parallel to the fused C(1)-C(6) bond.

[reaction: see text] The BF(3)-catalyzed rearrangement of cyclobutene-fused m- and p-substituted diarylhomobenzoquinones exclusively gave the keto-alcohols via a Wagner-Meerwein vinyl-anion migration followed by the annulation of a delta-located endo-aryl group. The Hammett treatments for the endo/exo substituent effects, as well as the kinetic solvent effects, indicated that this reaction proceeds through the concerted S(N)2-like mechanism involving a rate-determining endo-aryl-assisted transition state.

[reaction: see text] Irradiation of homonaphthoquinones with spiro-linked dibenzocycloheptene rings brings about the Norrish type II reaction to give polycyclic alcohols via a stereospecific 1,7-hydrogen abstraction of the less stable twist-boat conformer.

Reaction of phenyldiazomethane (1) with tetrafluoro-1,4-benzoquinone (2a) gave isomeric mixtures of stilbenes (3, cis/trans=4.7) and spirooxetanes (4a, cis/trans=1.1) via zwitterion intermediates. Similarly, tetrabromo-1,4-benzoquinone (2c) provided 3 and spirooxetane (4c); however, the cis/trans ratio of 3 dropped to 2.3 and 4c was solely the trans isomer. On the other hand, reaction with tetraiodo-1,4-benzoquinone (2d) afforded no spirooxetane and gave a further reduced isomer ratio of 3 of 1.9.

Fulleroids, obtained from the 1,3-dipolar cycloaddition of fullerene with a diazoalkane, have a [5,6]-open methylene bridge and two highly twisted bridgehead double bonds. The [H,H]- and [H,CN]-substituted fulleroids were found to display significantly enhanced and regioselective Diels-Alder addition as compared with the [6,6] closed methanofullerene and C(60) with 2,3-dimethyl-1,3-butadiene, but reduced and nonregioselective addition with cyclopentadiene. NMR analysis of the 1:1 adduct and quantum calculations indicated that the high reactivity and the regioselective addition are due to pi-orbital misalignment at the bridgehead double bond.

The acid-induced reaction of bis(p-chlorophenyl)homobenzoquinone epoxide gave the dual ipso/ortho intramolecular SE2-Ar products associated with the π-aryl participated oxirane ring opening, whereas bis(p-tolyl)- and diphenyl-substituted homologues provided only the ortho products.

Reaction of phenyldiazomethane (1) with tetrafluoro-1,4-benzoquinone (2a) gave isomeric mixtures of stilbenes (3, cis/trans=4.7) and spirooxetanes (4a, cis/trans=1.1) via zwitterion intermediates. Similarly, tetrabromo-1,4-benzoquinone (2c) provided 3 and spirooxetane (4c); however, the cis/trans ratio of 3 dropped to 2.3 and 4c was solely the trans isomer. On the other hand, reaction with tetraiodo-1,4-benzoquinone (2d) afforded no spirooxetane and gave a further reduced isomer ratio of 3 of 1.9.

Thermolysis of diphenyl- and biphenyl-2,2′-diyl-substituted homobenzoquinones 1 and homonaphthoquinones 2 with substituents X3(= Me, Cl, Br) has been investigated at 100 °C. The biphenyl-2,2′-diylhomoquinones 1 and 2 bearing halogeno substituents were thermolysed to 2-(9-halogenofluoren-9-yl)-1, 4-benzoquinones 8g, h and -1,4-naphthoquinones 19e, f, respectively, via a cyclopropane ring-opening reaction. The diphenylhomoquinones were thermally less labile so that only ones bearing a bromo substituent underwent a cyclopropane ring-opening to afford a different type of product, 2-bromo-3-diphenylmethylene-2, 3-dihydro-1,4-benzoquinones 3c–e and -1,4-naphthoquinone 10, respectively. The product change was attributed to the steric requirement of the intermediary allyl cations. On further heating, compounds 3c–e were converted into xanthylium salts via a 6π electrocyclization, whereas compound 10 was transformed into the coupling dimer via an allyl radical. The different behaviour of the bromo quinones 3c–e and 10 was interpreted on the basis of Frontier Molecular Orbital considerations.

Substituted diphenyldiazomethanes[(x-C6H4)2CN2; x=p-OCH3, p-CH3, H, p-Cl] were found to react with 2,5-dichloro-p-benzoquinone at its conjugated C=C and C=O bonds to give bicyclic diones and poly(2,5-dichlorohydroquinone benzhydryl ether)s respectively, obeying the second-order kinetic law. The product ratios of the polyethers to the bicyclic diones increased from 1.1 to 8.1 with the electron-donating ability of the substituents. The individual rate constants were well correlated with the Hammett equation: logk3=−2.15–1.55 σ (r=0.996) and logk4=−2.03–1.85 (σ0+0.515Δ\barσR+) (r=1.00) for the bicyclic diones and polyethers processes respectively. The presence of methanol as a trapping agent stopped the polymerization completely and afforded the methanolysis product, though no essential change was found in the formation of the bicyclic dione.

Unsubstituted 1,4-benzoquinone (1a) reacted with diphenyldiazomethane (DDM) at the C=C double bonds to give dihydroxy-3H-indazole (2a) and its benzhydryl ether (3a) together with benzodipyrazole derivative (4a). Similarly, reactions of 2-chloro- and 2,3-dichloro-1,4-benzoquinones (1b and 1c) with DDM yielded the corresponding dihydroxy-3H-indazoles (2b, 2b′, and 2c) and their benzhydryl ethers (3b, 3b′, and 3c) along with 5–13% benzophenone (6). On the other hand, reaction of 2,6-dichloro-1,4-benzoquinone (1e) with DDM gave bicyclic 5e and tricyclic diones (7e), together with benzophenone dimethyl acetal (9) in the presence of added methanol. In the same conditions, 2,3,5-trichloro-1,4-benzoquinone (1f) provided bicyclic dione (5f) and 9. Formation of 6 and 9 was interpreted as arising from the hydrolysis and methanolysis of the 1:1 betaine intermediates given by the addition of DDM to the quinonoid C=O double bonds. The C=O addition increased with increasing chlorine substituents.

Several phenyldiazomethanes easily decompose to cis- and trans-stilbenes when treated with catalytic amounts of copper perchlorate or copper bromide at 20°C. The preferential formation of cis isomer is particularly noteworthy. The stereochemistry and the mechanism of these reactions will be discussed.

Unsubstituted 1,4-benzoquinone (1a) reacted at the C=C double bond with 9-diazofluorene (9-DF) to give norcarene dione 2a and 4,7-dihydroxy-3H-indazole 4a. Similarly, the reaction of 2-chloro-1,4-benzoquinone (1b) with 9-DF yielded norcarene dione 2b and 4,7-dihydroxy-3H-indazole 4b, together with tricyclic dione 3b. 2,3-dichloro-1,4-benzoquinone (1c) and 9-DF produced norcarene dione 2c, 4,7-dihydroxy-3H-indazole 4c, and its fluorenyl ether 5c. Reactions of 2,5- and 2,6-dichloro- and trichloro-1,4-benzoquinones (1d, 1e, and 1f) with 9-DF provided norcarene diones 2d, 2e, and 2f and tricyclic diones 3d and 3e, respectively. On the other hand, tetrachloro-1,4-benzoquinone (1g) converted 9-DF into 9,9′-bifluorenylidene possibly via a 1:1 betaine intermediate arising from the C=O double bond addition. These results were markedly different from those of the previous diphenyldiazomethane reactions and are discussed in terms of structural changes of these diazoalkanes.