A thorough understanding of the mechanistic steps that occur in organometallic processes is crucial to the development of new, increasingly sophisticated transformations. This microreview discusses an unusual class of organometallic reactions that occur through formal Type I dyotropic rearrangements, defined as processes involving the interchange of two groups along a stationary scaffold by breaking and reforming two σ bonds in which at least one σ bond is a M–X bond. Examples are subdivided into two categories – stoichiometric and catalytic – and further classified by the number of atoms across which the migrating groups interchange positions. The metal can either serve as the migrating group or function as part of the stationary scaffold. Furthermore, these rearrangements can proceed through a wide variety of different mechanisms that include oxidative insertion/reductive elimination, radical processes, or pathways in which the metal does not change oxidation state.

Regioselectivity in the aziridination of silyl-substituted homoallenic sulfamates is readily diverted to the distal double bond of the allene to yield endocyclic bicyclic methyleneaziridines with excellent stereocontrol. Subsequent reaction with electrophilic oxygen sources initiates facile rearrangement to densely functionalized, fused azetidin-3-ones in excellent d.r., effectively transferring the axial chirality of the allene to central chirality in the products. The steric nature of the silyl group dictates which of the two rings of the fused azetidin-3-one will undergo further functionalization, providing an additional element of diversity for the preparation of enantioenriched azetidine scaffolds with potential biological activity.

Regioselectivity in the aziridination of silyl-substituted homoallenic sulfamates is readily diverted to the distal double bond of the allene to yield endocyclic bicyclic methyleneaziridines with excellent stereocontrol. Subsequent reaction with electrophilic oxygen sources initiates facile rearrangement to densely functionalized, fused azetidin-3-ones in excellent d.r., effectively transferring the axial chirality of the allene to central chirality in the products. The steric nature of the silyl group dictates which of the two rings of the fused azetidin-3-one will undergo further functionalization, providing an additional element of diversity for the preparation of enantioenriched azetidine scaffolds with potential biological activity.

Nitrogen-containing stereotriads, which are defined as compounds with three adjacent stereodefined carbon atoms, are common structural motifs in several biologically relevant compounds. The 1,3-diamino-2-ol motif in particular is an important pharmacophore for which there are limited stereoselective synthetic approaches. In this communication, we describe the aminohydroxylation of a series of bicyclic methylene-aziridines obtained from the aziridination of a series of homoallenic carbamates. The unusual electronic and steric features of these useful heterocyclic scaffolds render the Os-catalyzed aminohydroxylation of the exocyclic alkene highly regio- and stereoselective. Rearrangement of the proposed N,O-aminal intermediate to a 1,3-diamino-2-one is followed by reduction with NaBH₄ to deliver the desired 1,3-diamino-2-ols in good yields with high diastereomeric ratios.

Benzylic functionalization is a convenient approach towards the conversion of readily available aromatic hydrocarbon feedstocks into more useful molecules. However, the formation of carbanionic benzyl species from benzyl halides or similar precursors is far from trivial. An alternative approach is the direct reaction of a styrene with a suitable coupling partner, but these reactions often involve the use of precious-metal transition-metal catalysts. Herein, we report the facile and convenient generation of reactive benzyl anionic species from styrenes. A Cu^I-catalyzed Markovnikov hydroboration of the styrenic double bond by using a bulky pinacol borane source is followed by treatment with KOtBu to facilitate a sterically induced cleavage of the CB bond to produce a benzylic carbanion. Quenching this intermediate with a variety of electrophiles, including CO₂, CS₂, isocyanates, and isothiocyanates, promotes CC bond formation at the benzylic carbon atom. The utility of this methodology was demonstrated in a three-step, two-pot synthesis of the nonsteroidal anti-inflammatory drug (±)-flurbiprofen.