Umpolung-Enabled Divergent Dearomative Carbonylations.

Although dearomative functionalizations enable the direct conversion of flat aromatics into precious three-dimensional architectures, the case for simple arenes remains largely underdeveloped owing to the high aromatic stabilization energy. We herein report a dearomative sequential addition of two nucleophiles to arene π-bonds through umpolung of chromium-arene complexes. This mode enables divergent dearomative carbonylation reactions of benzene derivatives by tolerating various nucleophiles in combination with alcohols or amines under CO-gas-free conditions, thus providing modular access to functionalized esters or amides. The tunable synthesis of 1,3- or 1,4-cyclohexadienes as well as the construction of carbon quaternary centers further highlight the versatility of this dearomatization. Diverse late-stage modifications and derivatizations towards synthetically challenging and bioactive molecules reveal the synthetic utility. A possible mechanism was proposed based on control experiments and intermediate tracking.

Intermolecular Dearomative 1,2-Amination/Carbonylation via Nucleophilic Addition of Simple Amines to Arene π-Bonds.

The incorporation of the privileged amino functionality is of paramount importance in organic synthesis. In contrast to the well-developed amination methods for alkenes, the dearomative amination of arenes is largely underexplored due to the inherently inert reactivity of arene π-bonds and selectivity challenges. Herein, we report an intermolecular dearomative aminofunctionalization via direct nucleophilic addition of simple amines to chromium-bound arenes. This multicomponent 1,2-amination/carbonylation reaction enables rapid access to complicated alicyclic compounds containing amino and amide functionalities from benzene derivatives under CO-gas-free conditions, which also represents the first application of nitrogen-based nucleophiles in η6 -coordination-induced arene dearomatizations.

Chemoselective 1,2-Reduction and Regiodivergent Deuteration of Chromium-Bound Arenes.

Herein, a general strategy for chemo- and regioselective 1,2-reduction of chromium-bound arenes was developed, thus providing rapid access to 1,3-cyclohexadienes. Selective arene activation via π-complexation along with the use of mild hydride Ph3 SiH can overcome the inherently low reactivity of arene π-bonds while tolerating various reduction-sensitive functional groups. Its versatility further enables a regiodivergent deuteration. Using different sequences of (non)deuterated hydride and acid reagents, the deuterated positions as well as the degrees of deuterium incorporation can be controlled precisely, which leads to a large and previously inaccessible chemical space for 1,3-cyclohexadiene isotopologues. A reasonable mechanism was proposed based on intermediate capture and control experiments. The synthetic value of this selective 1,2-reduction was demonstrated in the formal total synthesis of (±)-galanthamine and (±)-lycoramine.

Dearomative Aminocarbonylation of Arenes via Bifunctional Coordination to Chromium.

Amides are ubiquitous in physical and life sciences. Given the significant abundance of arenes, dearomative aminocarbonylation of arenes would lead to a large and underexplored chemical space for amide discovery. However, such reactions are challenging due to the high degree of resonance stabilization and selectivity issues. Herein, we disclose an unprecedented dearomative trifluoromethylative aminocarbonylation of arenes via bifunctional coordination to chromium, providing a modular platform for the construction of amides possessing trifluoromethyl (CF3 ) groups and three-dimensional rings. Its versatility further enabled a switchable difluoromethylation or trifluoromethylation aminocarbonylation of arene C-H bonds. A possible mechanism was proposed based on control experiments. Finally, the synthetic utility was well demonstrated by diverse applications in the total synthesis of CF3 -functionalized amide-type drugs, including praziquantel, nateglinide, maraviroc and alloyohimbane.