Anhydrides creation

The creation of the N—N bond as the last step of the ring synthesis is common in indazoles and very rare in pyrazoles. In indazoles this method is well known (type B synthesis (67HC(22)l), for example, the dehydration of oximes (570) with acetic anhydride yields 1-acetylindazoles (571), and in basic medium the indazole 1-oxides (573) are formed from the nitro derivatives (572). 

The creation of selective catalysts for such complex reactions seems to be an especially difficult problem. Nevertheless, surprisingly, selective catalysts have been developed for complex reactions, which can be exemplified by the oxidation and ammoxidation of propylene, oxidation of butene and even butane to maleic anhydride (which requires seven oxygen atoms). Such reactions are usually performed over V and Mo oxide systems [4, 6, 8-10]. High selectivity of these systems is presumably provided by a special structure of the catalyst surface that allows control... 

The Diels-Alder reaction is a well-established synthetic method that allows the creation of two new carbon-carbon bonds and leads to the formation of six-membered rings. Eventually, the photochemical reaction can advantageously compete with the thermal process. For instance, anthracene undergoes thermal and photochemical Diels-Alder reactions with alkenes, but the photoinduced addition of maleic anhydride to the homochiral anthracene, as depicted in Scheme 9.28, is faster than the thermal reaction and occurs with excellent diastereoselectivity (only one diastereoisomer) [42]. 

It has been suggested that organic compounds occluded between the vanadium phosphate layers cause this disorder [78]. The disorder may be derived from a number of structural modifications a missing oxygen atom, an inversion from a trans- to a cis- vanadyl position, or from the modification of the V—O bond strength. It is proposed that these defects can all cause the creation of new active centers for butane activation. Furthermore, Cornaglia and coworkers [79] also report an increase in selectivity to maleic anhydride as the disorder in the (100) plane decreases. 

Recently, it has been found that the elimination of the hydroxylamine from a nitroxide-capped polymer occurs particularly facilely upon the controlled monoaddition of maleic anhydride and maleimide derivatives under the creation of a very useful functional end group, that is, the often detrimental side reactions can also be put to good use.115... 

Reduction of the anhydride gave 103 with complete regioselectivity in favour of the carbonyl next to the acetate but without stereoselectivity. This doesn t matter as treatment with acid initiated a rearrangement - cyclisation sequence giving a the alcohol 104 after hydrolysis of its formate. This time there is complete stereoselectivity in the creation of three new chiral centres. 

As an example of the first approach may be considered creation of a selfoc based on copolymeric matrix from DAIP-a and maleic anhydride (MA) [67, 68] with conversion of monomers of 30-60%. The polymeric matrix obtained is more plastic than the matrix from homopolymer DAIP with analogous conversion of the monomer, which allowed production of selfoc samples with relatively large diameter d 6-8 mm) with the refractive index gradient An = 0.035. Therewith, definite difficulties are encountered at fixing the created RID, associated with the reverse diffusion and partial evaporation of the monomer-diffusate that penetrated into the matrix [67, 68]. 

---