Bis-adducts

It was, however, found 22) that when the pyrrolidine enamine of cyclohexanone was allowed to react with an excess of -nitrostyrene, a bis adduct (46), made up of one molecule of the enamine and two molecules of olefin, was obtained in addition to the monoadduct. That the bis adduct is not derived from the monoadduct was shown by the latter s failure to react with (9-nitrostyrene. Therefore, this adduct must be formed by the addition of the olefin to the dipolar intermediate (47), as shown in the following scheme. 

Kuehne and Foley (29) have found that the reaction of the pyrrolidine enamine of butyraldehyde with 2 equivalents of (8-nitrostyrene also led to a bis adduct with the structure as shown in 48. 

The reaction of morpholine enamine of cyclohexanone with 1 mole of phenyl isocyanate has been reported (30,31) to give the monoadduet (49), consisting largely of the trisubstituted isomer, and with 2 moles of phenyl isocyanate, the bis adduct (50). That the bis adduct is a dicarboxyanilide rather than a urea derivative (32) such as 51 was shown by its mild hydrolysis to the ketone (52). Reaction of the morpholine enamine of 2-methylcyclo-... 

Alkyl derivatives such as 1,4-S6(NR)2 and S4(NR)4 can be synthesized by reacting S2CI2 with primary amines RNH2 in an inert solvent. Compounds such as 1,4-S2(NR)4 (R = —C02Et) are now also well characterized.The bis-adduct [Ag(S4N4H4)2]" " has been isolated as its perchlorate this has a sandwich-like structure and is unique in being S-bonded rather than N-bonded to the metal ion. ... 

The reaction of dichlorocarbene with 2 f-thiachromen (42) was exceptional since it gave none of the expected adduct but rather the products of substitution at the 2- (43) and 4-position (44) together with a bis-adduct of unknown structure. The substitution products could arise by reaction of the ambident anion 45 with dichlorocarbene, but the absence of these products in the same reaction of 4jy-thiachromen argues against this mechanism. The... 

Phenylpyrazole, upon reaction witii PdCl, forms tiie bis-adduct (1-Phpz)2 PdCl2 (73IC1216 75AJC1259), whichaflerprolongedreaction withPdCl " forms... 

Diacetylene reacts with diazomethane in an ether solution at 0°C to form 5-ethynylpyrazole (80) (65ZOR610). The second diazomethane molecule adds to the remaining triple bond much more slowly. The bis adduct, 5,5 -dipyrazole (81), was isolated in 35% at a 1 2 diacetylene diazomethane molar ratio. 

Aminoacroleins enter the transamination reaction with 1,2-diaminoethane to furnish bis adduct 217, whereas with 1,2-diaminobenzene they yield the 2 2 macrocyclic adduct 218 (77CZ161). 

Evidently, the reaction proceeds via the formation of bis-adduct 289 which undergoes cyclization to dihydropyridine 290. A similar reaction with methoxybutenone, but in the presence of ammonia, which is likely to involve replacement of methoxy group, has been described (80MI2). 

Equimolar amounts of anthracene,/ -benzoquinone, and aluminum chloride give the faintly yellow adduct in 15 minutes. The product is unstable to heat turning yellow at 207°, turning red at 210°, and slowly charring. When 2 molar equivalents of anthracene are used, the bis adduct is obtained, mp 230°, unobtainable in the absence of the catalyst. 

Bis(alkylsulfonyl)methanes361,363 or bis(phenylsulfonyl)methane362 readily reacted with aldehydes in the presence of bases to afford /1-hydroxysulfones or bis-adducts. For example, bis(ethylsulfonyl)methane was found to react with salicylaldehyde in the presence of piperidine, affording 2-ethylsulfonylbenzofuran in a good yield363. 

The result of the cycloaddition of cyclopentadiene with methylbenzoquinone (Scheme 6.20) is also interesting. In 5.0m LP-DE, diasteroisomeric bis adducts are formed, while in the absence of LP-DE, only one 1 1 adduct is obtained quantitatively. 

Palladium(II) acetate reacts with N,N, N"-triphenylguanidine ( = HTpg) in warm benzene to form a bis-adduct which, under more forcing conditions, converts to the novel dinuclear guanidinate-bridged complex [Pd(/L-Tpg)... 

The diolefin 1064 gives rise to the isoxazoline 1065, which cannot eliminate tri-methylsilanol 4 [122]. Cychzation of the co-nitroolefin 1066 with trimethylchloro-silane (TCS) 14/triethylamine at -35 °C then HCl-induced removal of trimethyl-silanol 4 leads, in 85% yield, to the dimer 1067, which is converted in two more steps into racemic pyrenophorin 1068 [112] (Scheme 7.39). Further cyclizations of co-nitroolefins [109] to monomeric or dimeric isoxazolines have been described. Conjugated dienes such as butadiene afford a mixture of the mono or bis adducts [115-117]. 

Dendrimers 5-8 were obtained by taking advantage of the versatile regiose-lective reaction developed in the group of Diederich [24], which led to macro-cyclic bis-adducts of Cgg by a cyclization reaction at the C sphere with bis-mal-onate derivatives in a double Bingel cyclopropanation [25]. Reaction of the dendritic malonates with Cgg, I2, and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene at room temperature afforded the corresponding cyclization products 5-8 (Fig. 2). The relative position of the two cyclopropane rings in 5-8 on the Cgo core was determined based on the molecular symmetry deduced from the and NMR spectra (Cs) as well as on their UV/Vis spectra. It is well estabhshed... 

The reaction of the same ylide 63 with dimethyl acetylenedicarboxylate (DMAD) in chloroform afforded the cyclazine 67, through aromatization of monoadduct 66 the azocine 69, which is formed through a second nucleophilic attack with ring expansion in the bis-adduct 68 and the pyrrolo derivative 71, which is formed by evolution of the bis-adduct 70 through a retro-Diels-Alder reaction (Scheme 3) <2001JOC1638>. 

Corsaro and co-workers studied the reaction of pyridazine, pyrimidine, and pyrazine with benzonitrile oxide and utilized H NMR spectral analysis to determine the exact structure of all the cyclized products obtained from these reactions <1996T6421>, the results of which are outlined in Table 1. The structure of the bis-adduct product 21 of reaction of pyridazine with benzonitrile oxide was determined from the chemical shifts of the 4- and 5-isoxazolinic protons at 3.76 and 4.78 ppm and coupled with the azomethine H at 6.85 ppm and with the 5-oxadiazolinic H at 5.07 ppm, respectively. They determined that the bis-adduct possessed /(-stereochemistry as a result of the large vicinal coupling constant (9.1 Hz). Similarly, the relative stereochemistry of the bis-adducts of the pyrimidine products 22-25 and pyrazine products 26, 27 was determined from the vicinal coupling constants. 

One synthetic approach involves cyclization of a substituted six-membered heterocycle which becomes the central ring of the product (6 6 6). For example, the reaction of 2,6-diaminopyridine with 2,2-dimethyl-l,3-dioxane-4,6-dione and trimethoxymethane gives the bis-adduct 118 which is a precursor to the angular tricyclic product 119 (Scheme 14) <2005AXCol>. 

Besides the use of porphyrins as azomethinic ylide derivatives, the porphyrin macrocycle can also be used to generate porphyrinic nitrile oxides 55 (Scheme 17) <04RCB(E)2192>. Thus, the treatment of oxime 54 with /V-bromosuccinimide in the presence of triethylamine, led to the formation of nitrile oxide 55, which was trapped in 1,3-DC reactions with dimethyl maleate and 2,5-norbomadiene to afford 56 and 57, respectively. In the reaction with 2,5-norbomadiene, if an excess of 55 was used, then the corresponding bis-adduct was obtained in good yield. 

In the particular scenario of the reaction of ie.vo-tctrakis(pcntafluorophenyl)porphyrin Id with the azomethine ylide, generated in situ from /V-mcthylglycine and paraformaldehyde, in refluxing toluene during 15 hours, the pyrrolidinochlorin derivative 62 was obtained as the main product (Scheme 19), together with a small amount of isobacteriochlorin 63 (bis-adduct, Figure 5). 

As shown above, porphyrins can be used as dienophiles and as dipolarophiles in DA and 1,3-DC reactions with a wide range of reactive dienes and 1,3-dipoles to achieve monoadducts of the chlorin type, as the main products, or related compounds. Furthermore, under certain conditions, bis-adducts of the iso- or bacteriochlorin types can be obtained depending on the 4% species used. 

Diethylzinc forms a colorless monoadduct with l,4-diazabicyclo[2,2,2]octane (dabco) 34 and an orange-colored bis-adduct with acridine.79 The mono-dabco adduct, Figure 14, crystallizes in the form of infinite zigzag chains, in which each diethylzinc moiety bridges two dabco units. The coordination environment about zinc is distorted tetrahedral, with Zn-C and Zn-N bonds ranging from 1.93(3) to 2.10(2) A and from 2.24(2) to 2.37(2) A, respectively. 

The rational synthesis of 3,8-methano[ 1 ljannulenone 12 started from 2-meth-oxy-l,4,5,8-tetrahydronaphthalene 25 which on reaction with dibromocarbene provided the bis-adduct 26. 

To avoid explosion hazards [70], a modified domestic microwave oven was used. Higher yields were obtained in shorter periods of time on use of microwave irradiation (39% yield after 20 min irradiation) in comparison with thermal conditions. Longer irradiation times led to a decrease in the yield of 75, because of increased bis adduct formation. 

Under the action of microwave irradiation, with toluene as a solvent, cycloadduct 76 was formed in 35% yield after 15 min at 800 W [72] this is an improvement on the yields obtained by conventional heating and probably occurs because of a decrease in the reversion of the cycloaddition in the shorter period of time needed for the irradiated reaction. It is remarkable that under microwave conditions the formation of bis adducts was not observed in these reactions. 

For the synthesis of the bis-cyclo-octatetraene compound [5] (Krummel et al, 1987 Auchter-Krummel and Mullen, 1991), cyclo-octatetraene dianion was quenched with tetrabromoneopentane to give the bis-adduct [23], which exists in an equilibrium between valence isomers [23a] and [23b]. Hexacycle [23a] was actually isolated in about 60% yield (Fig. 2) (Krummel et al, 1987). Accordingly, in the subsequent dehydrogenation, the formation of [23a] must be avoided by working at low temperatures in this case it was possible to deprotonate the originally formed isomer [23b], obtaining a... 

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