Tertiäre α‐Silylalkohole mittels diastereoselektiver Kupplung von 1,3‐Dienen und Acylsilanen, eingeleitet durch enantioselektive kupferkatalysierte Borylierung

Zinc-Catalyzed Enantioselective Formal (3+2) Cycloadditions of Bicyclobutanes with Imines: Catalytic Asymmetric Synthesis of Azabicyclo[2.1.1]hexanes

The cycloaddition reaction involving bicyclo[1.1.0]butanes (BCBs) offers a versatile and efficient synthetic platform for producing C(sp3)-rich rigid bridged ring scaffolds, which act as phenyl bioisosteres. However, there is a scarcity of catalytic asymmetric cycloadditions of BCBs to fulfill the need for enantioenriched saturated bicycles in drug design and development. In this study, an efficient synthesis of valuable azabicyclo[2.1.1]hexanes (aza-BCHs) by an enantioselective zinc-catalyzed (3+2) cycloadditions of BCBs with imines is reported. The reaction proceeds effectively with a novel type of BCB that incorporates a 2-acyl imidazole group and a diverse array of alkynyl- and aryl-substituted imines. The target aza-BCHs, which consist of α-chiral amine fragments and two quaternary carbon centers, are efficiently synthesized with up to 94 % and 96.5:3.5 er under mild conditions. Experimental and computational studies reveal that the reaction follows a concerted nucleophilic ring-opening mechanism of BCBs with imines. This mechanism is distinct from previous studies on Lewis acid-catalyzed cycloadditions of BCBs.

Synthesis of Cyclic Allylborates from 1,3-Dienes and a Diboron Reagent

The synthesis of cyclic allylborates was achieved by the reaction of 1,3-dienes and B₂ pin₂ using a copper catalyst. Several 1,3-dienes were converted to the corresponding cyclic allylborates in moderate to high yields. The cyclic allylborate obtained could be used in several organic transformations such as allylation of electrophiles and Suzuki-Miyaura coupling.

Oxyenamides as Versatile Building Blocks for a Highly Stereoselective One-Pot Synthesis of the 1,3-Diamino-2-ol-Scaffold Containing Three Continuous Stereocenters

A highly diastereoselective one-pot synthesis of the 1,3-diamino-2-alcohol unit bearing three continuous stereocenters is described. This method utilizes 2-oxyenamides as a novel type of building block for the rapid assembly of the 1,3-diamine scaffold containing an additional stereogenic oxygen functionality at the C2 position. A stereoselective preparation of the required (Z)-oxyenamides is reported as well.

Copper-Catalyzed Highly Selective Protoboration of CF3 -Containing 1,3-Dienes

The copper-catalyzed highly selective protoboration of CF₃ -containing conjugated diene with proton source and B₂ Pin₂ has been developed. This chemistry could suppress the well-known defluorination and provide borated reagents with an intact CF₃ -group. Further studies indicated that the functional group tolerance of this chemistry is very well, and the products could be used as versatile precursors for different types of transformations. Importantly, using chiral diphosphine ligand, we have developed the first example for using such starting material to synthesis allylic boron-reagents which bearing a CF₃ -containing chiral center. Notably, the reaction mechanism was intensively studied by DFT calculations, which could reveal the reason that defluorination was inhibited.