Copper-catalyzed boroacylation of allenes to access tetrasubstituted vinylboronates

Cooperative Cu/Pd-Catalyzed 1,5-Boroacylation of Cyclopropyl-Substituted Alkylidenecyclopropanes

A Cu/Pd-cocatalyzed 1,5-boroacylation of cyclopropyl-substituted ACPs with B2pin2 and acid chlorides has been developed. Using cyclopropyl-substituted ACPs as the starting material, a broad range of 1,5-boroacylated products with multiple functional groups was prepared in good yields with excellent regio- and stereoselectively. Both aromatic and aliphatic acid chlorides were tolerated in this reaction.

Copper-catalyzed 1,2-Borylacylation of 1,3-Enynes: synthesis of β-Alkynyl ketones

A copper catalyzed 1,2-borylacylation of 1,3-enynes with B₂pin₂ and acid chlorides has been developed. Using readily available 1,3-enynes, B₂pin₂ and acid chlorides as substrates, a range of highly functionalized α,α-disubstituted β-alkynyl ketones were readily prepared under mild conditions in moderate to good yields. The borylacylated products can be easily derivatized to give several valuable structures. Notably, treatment of the products with NaBO₃·4H₂O provided 1,2-allenyl ketones, which is proposed to proceed via a retro-aldol process of the corresponding homopropargyl alcohols.

Copper catalysed protoboration of allenyl-Bdans: efficient synthesis of β-boryl allyl-Bdans

A novel strategy for the selective synthesis of β-boryl allyl-Bdan derivatives by employing Cu-catalyzed protoboration of allenyl-Bdan derivatives was developed.

Regio- and Stereoselective Synthesis of Multi-Alkylated Allylic Boronates through Three-Component Coupling Reactions between Allenes, Alkyl Halides, and a Diboron Reagent

Multisubstituted allylic boronates are attractive and valuable precursors for the rapid and stereoselective construction of densely substituted carbon skeletons. Herein, we report the first synthetic approach for differentially 2,3,3-trialkyl-substituted allylic boronates that contain a stereodefined tetrasubstituted alkene structure. Copper(I)-catalyzed regio- and stereoselective three-component coupling reactions between gem-dialkylallenes, alkyl halides, and a diboron reagent afforded sterically congested allylic boronates. The allylboration of aldehydes diastereoselectively furnished the corresponding homoallylic alcohols that bear a quaternary carbon. A computational study revealed that the selectivity-determining mechanism was correlated to the coordination of a boryl copper(I) species to the allene substrate as well as the borylcupration step.

Recent advances in the stereoselective synthesis of acyclic all-carbon tetrasubstituted alkenes

Alkenes bearing four carbon-based groups are ubiquitous motifs in chemical sciences due to their various applications from medicinal to materials chemistry, and as chemical platforms for the synthesis of complex, chiral molecules. As such, tremendous research efforts are currently ongoing in order to develop general procedures for the challenging stereoselective synthesis of all-carbon tetrasubstituted alkenes, especially for acyclic structures. Since classical approaches to carbon-carbon double bonds are not suitable for the high steric demand around tetrasubstituted alkenes, a variety of unique approaches to access these privileged functional groups have been developed in recent years. This review article highlights the most significant developments in the field from 2007 to 2020, with an emphasis on the mechanisms and remaining limitations of these contemporary methods. Specifically, recent advances in internal alkyne carbofunctionalizations, in multicomponent couplings or other cross-couplings from nucleophilic or electrophilic alkenyl partners, and in the development of miscellaneous methods, are discussed.