Suggestion Schemes

The mechanism and the stereochemistry of the reaction was studied using borodeuteride andfor deuterium oxide (480) and a reaction pathway was suggested (Scheme 93). 

The light-induced rearrangement of 2-phenyl- to 3-phenyl-thiophene may occur by a similar mechanism an equilibrium between the bicyclic intermediate (26) and the cyclopro-penylthioaldehyde (27) has been suggested (Scheme 2). The formation of IV-substituted pyrroles on irradiation of either furans or thiophenes in the presence of a primary amine supports this suggestion (Scheme 3). Irradiation of 2-phenylselenophene yields, in addition to 3-phenylselenophene, the enyne PhC=C—CH=CH2 and selenium. Photolysis of 2-phenyltellurophene furnishes solely the enyne and tellurium (76JOM(108)183). 

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It is inferred that intermediate formation can occur, and these experimental observations suggest Scheme XXIII. 

For the thermochemistry of pure decabromobiphenyl ether, the following mechanistic scheme has been suggested (Scheme 2) (ref. 11). 

A suggested scheme for pyrazine formation in roasted coffee.3... 

A suggested scheme for the formation of oxazoles from a-aminoketones.3... 

Figure 6. Suggested scheme for replacing the Kroll process by plasma techniques.

Amino and 5-amino-l,2,4-thiadiazoles both exist predominantly in the amino forms. The IR spectrum of 5-mercapto-l,2,4-thiadiazole does not show a clear SH absorption as would be expected for structure 6 and therefore the thione tautomers 7 and 8 have been suggested (Scheme 2). Similarly, IR evidence suggests that perthiocyanic acid exists as the dithione 9 as opposed to stmcture 10 <1984CHEC(6)463>. 

The suggested scheme for ethylene formation is dimerization of methylene-metal complexes ... 

Scheme 2. Suggested Scheme for the Reduction of RFeCp(C0)2 with LAH (R = Me, Et).

The seemingly plausible Scheme shown in 4 is inconsistent with the results of the 13C0 labeling study as are most schemes which do not involve CO insertion for the chain propagation. We believe that ethylene arises from the same sequence of steps as the other hydrocarbon products. The role of the second metal center in the reduction cannot be described. We believe that the iron-iron bond is cleaved early in the reaction since the reduction in the presence of PBu3 produced the unsubstituted species, LiCpFe(C0)2. While there is too little information currently available to assess the importance of Scheme 3, our results on reduction in this iron system are not consistent with the normal CO insertion mechanism or with carbene oligomerization. We suggest Scheme 3 until further research can be accomplished. 

To explain the formation of p-lactam formation two plausible mechanisms have been suggested (Scheme 2.320). 

For acyl nitronates of the general formula RCH=N(0)OAc, two types of rearrangements were suggested (Scheme 3.102), which are associated, respectively, with 1,2-migrations of the N-oxide oxygen atom (223) or the OAc fragment (219). 

Transfer of the acyl group from the acylzirconocene chloride to aluminum (transmetala-tion) by treatment with aluminum chloride has been reported to give an acylaluminum species in situ, and the possibility of the acylaluminum acting as an acyl anion donor has been suggested (Scheme 5.5) [7]. However, the acyl anion chemistry through this trans-metalation procedure appears to be limited since only protonolysis to the aldehyde proceeds in good yield, which could be achieved by direct hydrolysis of the acylzirconocene chloride. 

Fig. 3 Suggested scheme for the transformation of layered titanate to anatase Ti02 nanoroad. The structure models presented are the projection along the nanotube axis, i.e., the [010] of the titanate. The final TiOz nanorod product shown is the (010) face of the anatase phase. Elaborated from the picture reported by Nian and Teng.165...

A chain-type variation, where the alcohol radical formed attacks an unexcited quinoline, has also been suggested (Scheme 12). °... 

The laboratory top management establishes communication channels within the laboratory departments that ertsure effective and efficient operation of the laboratory. Activities that help corrrmrmication include for example, meetings, irrformation on notice boards, a laboratory jotrmal , e-mails and web sites, employee strrveys and suggestion schemes etc. 

It would be difficult, at this stage, to present a properly argued preference between schemes A and B in the Introduction as the more faithful representation for the disrotatory electrocyclic ring-opening of cyclohexadiene. Chemical intuition (at least that of the authors) would suggest scheme B, but scheme A is on the textbook pages and, as has been shown by the SC description of the 1,3-dipolar addition of fulminic acid to ethyne, a heterolytic scheme remains a definite possibility. 

A mechanism involving formation of the Af-lithinm derivative of 5h by proton abstraction with higher-order cyanocnprate, followed by C—N coupling of cyano cuprate, was suggested (Scheme 49) ". ... 

In 1949 Coulson and Fisher[15] introduced the idea of nonlocalized orbitals to the VB world. Since that time, suggested schemes have proliferated, all with some connection to the original VB idea. As these ideas developed, the importance of the spin degeneracy problem emerged, and VB methods frequently were described and implemented in this context. We discuss this more fully later. 

A series of pyrazolo[3,4- / pyrimidines 310 were obtained via reacting carbodiimide 308 with amines. Carbodiimide 308 was obtained by teacting ester 306 with triphenylphosphine and bromine, and then reacting the so-formed 307 with phenyl isocyanate. The intermediacy of 309 is suggested (Scheme 23) <2004JHC393>. 

The similarity of the results obtained with phenyl azide and N-phenyl-hydroxylamine in benzene/TFA indicates that both reactions proceed by similar mechanisms, but N-phenylhydroxylamine in benzene/TFSA produces a higher yield of the C-substitution products 27 and 28 As previously suggested (Scheme 5), N-phenylhydroxylamine can be doubly protonated to yield the dication 11 in strong acids, but the more weakly basic phenyl azide is less likely to be doubly protonated. The differences observed between the behavior of N-phenylhydroxylamine and phenyl azide in TFSA may be due to the inability of phenyl azide to directly generate 11. 

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