Metallo-de-hydrogenation

Metallation with Organometallic Compounds Metallation or Metallo-de-hydrogenation... 

Schemes 9-3 and 9-4 are sequences of two substitutions, first a metallo-de-hydrogenation, followed by a halogeno-de-metallation. Scheme 9-3 is analogous to the well known electrophilic aromatic sulfonation of anthraquinone in position 1. This isomer is obtained only if the reaction is run in the presence of catalytic amounts of mercury (ii) salts. Nowadays, however, larger effort is devoted to either replace mercury by other catalysts, or in the search for processes leading to (practically) complete recovery of the mercury. This case raises two questions with respect to the reaction sequence (9-3) first, whether it is possible to apply a one-pot process with catalytic amounts of a mercury compound (not necessarily HgO) to the synthesis of compounds 9.5, and second, whether mercury can be completely recycled in processes using either stoichiometric or catalytic amounts of the element.

The literature on metallo-de-hydrogenations of aliphatic diazo compounds is, in contrast to that on substitutions with classical electrophilic reagents, fairly large. It includes the monovalent metals Li, Na, and Ag, the divalent metals Mg, Zn, Cd, and Hg, the trivalent metal Tl, and the tetravalent metals Ge, Sn, and Pb. In addition, substitutions with the hetero atoms B, As, Sb, Bi, and Si, as well as metallo-de-metallations are reported in the literature. Although the synthesis of diethyl mer-cury(bisdiazoacetate) (9.4) was performed quite early (Buchner, 1895), the majority of papers on metallation was published in the 1960 s and 1970 s. ... 

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