Organic rearrangements

In addition to complex-formation, the interaction of transition-metal atoms with organic substrates at low temperatures can result in rearrangement of the organic moiety without complexation. Two such reactions have already been briefly mentioned, namely, the polymerization of hexafluoro-2-butyne by Ge and Sn atoms (72) and the polymerization of styrene by Cr atoms (i 1). In this section we shall briefly summarize some of these transition-metal-atom-promoted, organic rearrangements. 

THE ENTHALPY CHANGE IN ORGANIC REARRANGEMENTS AND THE ELECTRONEGATIVITY SCALE... 

The problem of precedents for the organic rearrangements required by the radical mechanism has been addressed and discussed by Wollowitz and Halpem. They reacted (n-Bu)3SnH, TBTH, in CgH with various bromide derivatives to generate the radicals and obtained some rearranged product, as shown for typical conditions in Scheme 8.3. 

Zeolites and clays have been used as effective acid microporous catalysts in certain organic rearrangements useful for the S5mthesis of fine chemicals. For instance, the Claisen rearrangement of allyl aryl ethers 10 followed by intramolecular hydroxyalkylation of the resulting olefin afforded 2-methyldihydrobenzofuran (11) (Scheme 6) [55]. 

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