Annex 1 Devising New Synthetic Pathways

To solve problems such as the one proposed in DPS try to apply a retroanalysis of the molecule to be synthesized, cutting its structure into readily available or easy to prepare sub-units. At this point look at the possibility to synthesize the target molecule from these sub-units using organometallic procedures that have found successful industrial applications. 

A simple example is offered by adiponitrile the sub-units used can derive from cutting the adiponitrile molecule into a four-carbon unit (butadiene) and two one-carbon units (HCN) as in the process shown in Section 5.4. It is also possible, however, to cut the same molecule into two three-carbon units 

An electrochemical procedure for acrylonitrile coupling has been industrially successful. Here a reductive acrylonitrile coupling is effected by the electrons coming from the cathode of an electrolytic cell. The first formed radical carbanion attacks the second acrylonitrile molecule. Uptake of a new electron from the cathode and of two protons gives adiponitrile in high yield [M. Baizer and D. E. Danly, Chem. Ind. (London), 1979, 435, 439]. 

Finally in carrying out the retroanalysis it is possible to retain the six-carbon skeleton of adiponitrile by starting from cyclohexane and ammonia. The former can be readily converted to adipic acid by catalytic oxidation (Chapter 2). 

Annex 2 Hints to Improve or to Develop Alternative Processes for the Synthesis of Aromatics Catalyzed hy Transition Metals 

---