Molecular Rearrangements

A review of pericyclic biosynthetic reactions reports that there are many 'pericyclase' enzymes in nature that catalyse such transformations. Using the Cope rearrangement as a model process, a report shows synergy between acceptor and donor groups can allow rational design of interrupted and aborted pericyclic reactions. The Brandi–Guarna rearrangement of 5-spirocyclopropane isoxazolidines has been investigated by computational methods to rationalize the competing formation of tetrahydropyridones and enaminones. The Nazarov cyclization has been reported to give substituted cyclopentenones with iodine as the catalyst. A thermal Overman rearrangement of enantioenriched cyclic allylic alcohols has been reported to give tertiary allylic amines. Ring expansion of in situ generated cyclopropylmethyl cations via Wagner–Meerwein rearrangement to cyclobutanes has been reported to involve a planar cyclopropylmethyl cation with loss of chiral information in the case of chiral precursors.