Coupling bis

A new electrolysis system comprising two metal redox couples, Bi(0)/Bi(III) and A1(0)/A1(III), has been shown to be effective for electroreductive Barbier-type allylation of imines [533]. The electrode surface structure has been correlated with the activity towards the electroreduction of hydrogen peroxide for Bi monolayers on Au(III) [578], Electroreductive cycliza-tion of the 4-(phenylsulfonylthio)azetidin-2-one derivative (502) as well as the allenecarboxylate (505) leading to the corresponding cycKzed compounds (504) and (506) has been achieved with the aid of bimetallic metal salt/metal redox systems, for example, BiCh/Sn and BiCh /Zn (Scheme 175) [579]. The electrolysis of (502) is carried out in a DMF-BiCh/Py-(Sn/Sn) system in an undivided cell by changing the current direction every 30 s, giving the product (504)in 67% yield. 

OXIDATIVE PHENOL COUPLING Bis(N-/i-propylsalicyUdeneaminate)cobalt(II). Vanadyl trichloride. 

An analysis of network formation shows that terminal bifunctionality must be very close to the ideal of two functional groups per molecule to produce a high quality vulcanizate. The quality of a vulcanizate can be related to the required number average molecular weight, MR, of a polymer in an equivalent random network (6). MR values can be determined for an idealized network formed by coupling bi- or monofunctional prepolymers—i.e., no nonfunctional molecules—using the expression ... 

Consider first the model described by Eqs (13.6), (13.7), (13.10), and (13.11) where the hannonic oscillator under study is coupled bi-linearly to the harmonic bath. The relevant correlation functions ( F(Z),.F(0) ) and (F(Z)F(0))c should be calculated with F = and its classical countei part, where Uj are coordin-... 

The tetraazamacrocycle 102 is the first known representative of tellurium-containing macrocycles. It was prepared in 80% yield by coupling bis-(o-formylphenyl) telluride (8IKGS121) with 1,2-diaminoethane [96JCS(D) 1203]. Reduction of 102 with NaBH4 gives rise to the tetraazamacrocyclic compound 103 [96JCS(D)1203]. 

A linear assembly formed through successive self-complementary coordination of meso-meso-coupled bis(imidazolyl zinc porphyrin) units can also transfer excitation energy along the one-dimensional array. In order to estimate the efficiency of this energy transfer, imidazolyl Mn porphyrin was added to the linear array of imidazolyl zinc porphyrins 52. The terminals of the array can accept complementary coordination with imidazolyl Mn porphyrin [114], As a result, the fluorescence of Zn porphyrin (0 = 0.053) in the one-dimensional array is quenched. This quenching never happens... 

In the presence of bismuth(lll) chloride-aluminum, allylic bromides have been found to react with aldehydes at room temperature in tetrahydrofuran-water to afford the corresponding homoallyhc alcohols in high yields (Wada et al, 1987). Water was found to play a crucial role since the allylation failed in pure tetrahydrofuran. Only a catalytic amount of bismuth chloride was needed to carry out the reaction. Bismuth(ill) chloride was reduced by aluminum to zero-valent bismuth, which could insert into the carbon-bromine bond of the allylic bromide to afford an allylbismuth intermediate as the reactive species. The allylation reaction could occur with the couple Bi(0)-Al(0) in tetrahydrofuran-water only in the presence of a catalytic amount of hydrobromic acid (Wada et al, 1990). Since bismuth(O) was postulated to be an intermediate oxidation state, the reaction was accomplished via an electrochemical redox pathway (Figure 4.1) in a two-phase system (Minato and Tsuji, 1988). Reactions mediated by Bi(0) as the only promotor were sluggish (Wada et ah, 1990). An exception was, however, reported with the coupling between p-nitrobenzaldehyde and allyl iodide in water (Chan and Isaac, 1996). 

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