Rearrangements

Rearrangement reactions can be powerful methods for the relay of stereochemistry, functional group interconversion, and altering the atomic connectivity. This chapter discusses various rearrangement reactions in organic chemistry. It highlights the most important reactions, addressing basic principles, advantages/disadvantages of the methodology, mechanism, and techniques for achieving laboratory success. The rearrangement reactions discussed include carbon-to-carbon migrations of carbon and hydrogen and other groups, carbon-to-nitrogen migrations of carbon, carbon to oxygen migrations of carbon, heteroatom to carbon migrations, and carbon to heteroatom rearrangements. Other rearrangements covered include electrocyclic rearrangements, sigmatropic rearrangements, and acyclic rearrangements. Cationic [1,2]-shifts are frequently employed in the rearrangement of pyrroles and thiophenes; these rearrangements are followed by loss of a proton to produce the aromatic system. Quasi-Favorskii rearrangements of ketones and ketals can be induced on treatment of appropriate substrates with a Lewis acid. The chapter also covers miscellaneous migrations namely, Hunsdiecker reaction, Jocic reaction, Truce–Smiles rearrangement, Dakin–West reaction, and Meinwald rearrangement.