A mild catalytic synthesis of alkynes via a tandem Pd-catalyzed decarboxylation/elimination of enol triflates is described. Key attributes of the method include readily available starting materials, broad functional group tolerance, and the ability to access terminal, internal, and halogenated alkynes. The preliminary scope of the reaction is demonstrated on 25 different examples with yields ranging from 63% to 96%.

The increasing synthetic utility of allenes in organic synthesis combined with their incorporation into a growing list of natural products and active pharmaceutical ingredients has stimulated an intense effort recently to identify efficient catalytic methods for their synthesis. In addition, as the only common functional group in organic chemistry that possesses axial chirality, efforts to discover new asymmetric catalysts for the enantioselective synthesis of axially chiral allenes has intensified as these substrates become more ubiquitous as chiral building blocks for downstream asymmetric methodologies. Nonetheless, despite this intensive effort, the ability to access racemic or chiral allenes from readily available starting materials using catalytic processes has yet to meet the demand of their expanding applications. The focus of this Perspective is to provide a critical assessment on the most recent developments in the field of catalytic syntheses of allenes (2011–2013) highlighting both the advantages and limitations associated with current approaches with a future outlook on the unmet synthetic need that still persists.Keywords: allenes; asymmetric synthesis; axial chirality; catalysis; chirality transfer

We wish to report our preliminary results on the discovery and development of a catalytic, asymmetric β-hydride elimination from vinyl Pd(II)-complexes derived from enol triflates to access chiral allenes. To achieve this, we developed a class of chiral phosphite ligands that demonstrate high enantioselectivity, allow access of either allene enantiomer, and are readily synthesized. The methodology is demonstrated on over 20 substrates, and application to the formal asymmetric total synthesis of the natural product, (+)-epibatidine, is also provided.

We report herein experimental and theoretical evidence for an aromatic Cope rearrangement. Along with several successful examples, our data include the first isolation and full characterization of the putative intermediate that is formed immediately after the initial [3,3] sigmatropic rearrangement. Calculations at the B3LYP/6-31G(d) level of theory predict reaction energy barriers in the range 22–23 kcal/mol for the [3,3]-rearrangement consistent with the exceptionally mild reaction conditions for these reactions. The experimental and computational results support a significant enthalpic contribution of the concomitant pyrazole ring formation that serves as both a kinetic and thermodynamic driving force for the aromatic Cope rearrangement.

The synthesis of 3,4,5-trisubstituted pyrazoles via a tandem catalytic cross-coupling/electrocyclization of enol triflates and diazoacetates is presented. The initial scope of this methodology is demonstrated on a range of differentially substituted acyclic and cyclic enol triflates as well as an elaborated set of diazoacetates to provide the corresponding pyrazoles with a high degree of structural complexity.