Problem generating starting materials

Addition of excess base in these reactions generates the dianionic starting material in Eq. 15.16. The intermediate shown in Eq. 15.19, which has a coordinated formyl group (C(O)H), has been isolated and characterized. Its counterpart in the OH reaction is a hydroxycarbonyl complex (see Problem 15.45) Both are inherently unstable, decomposing to the hydrido complex by elimination of CO or CO,. When these reactions are attempted with Cr(CO)fc, the final product is not the expected [HCriCO) ] anion, but rather a bridging hydride complex "... 

To prepare crystalline surfaces, usually the starting material is a suitable, pure, three-dimensional single crystal. From this crystal, a slice of the desired orientation is cut. Therefore the crystal must be oriented. Orientation is measured by X-ray diffraction. Hard materials are then grounded and polished. Soft materials are cleaned chemically or electrochemically. The surfaces are still mechanically stressed, contaminated, or chemically changed, e.g. oxidized. In principle, electrochemical processes in liquid can be used to generate clean crystalline surfaces. The problem is that an electrochemical setup is not compatible with an UHV... 

Generating tin hydride in situ by using a catalytic amount of tributyltin chloride and sodium cyanoborohydride [24] did not solve the problem. Although this method inherently produces the desired low concentration of n-BujSnH to promote cyclization over direct reduction of the starting material and reduces drastically the amount of tin residue, a displacement reaction between solvent and the benzylic hydroxyl group takes place. Eventually, the best method was the use of high dilution conditions at approximately 70 °C in benzene followed by the KF workup. 

In summary, the purpose of this problem is not to solicit identification of a leaving group, but rather to induce consideration of the different reaction processes that can occur. Through such an understanding, starting materials and reaction conditions can be chosen that maximize the chances of generating a desired product with minimal side reactions. 

By contrast to the normally unstable diazonium salts, the one generated in situ under the conditions of this process is stable and so there is no serious safety problem and the use of anilinesulfonic acid as starting material turns out to be... 

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