Silylarene Hydrogenation: A Strategic Approach that Enables Direct Access to Versatile Silylated Saturated Carbo‐ and Heterocycles

Abstract

We report a method to convert readily available silylated arenes into silylated saturated carbo- and heterocycles by arene hydrogenation. The scope includes alkoxy- and halosilyl substituents. Silyl groups can be derivatized into a plethora of functionalities and find application in organic synthesis, materials science, and pharmaceutical, agrochemical, and fragrance research. However, silylated saturated (hetero- ) cycles are difficult to access with current technologies. The yield of the hydrogenation depends on the amount of the silica gel additive. This silica effect also enables a significant improvement of a previously disclosed method for the hydrogenation of highly fluorinated arenes (e.g., to all-cis-C H F ).

Hydrogenation of (Hetero)aryl Boronate Esters with a Cyclic (Alkyl)(amino)carbene–Rhodium Complex: Direct Access to cis‐Substituted Borylated Cycloalkanes and Saturated Heterocycles

“…[9] Herein, we report am ethod for the selective hydrogenation of substituted aryl boronate esters with ac yclic (alkyl)(amino)carbene (CAAC)-ligated rhodium complex. [10][11][12][13][14] This approach enables the hydrogenation of aryl and heteroaryl boronate esters with retention of the boronate ester functional group (Scheme 1b). Hence,i toffers as traightforward, chemo-, and stereoselective strategy to access elusive,d iversely substituted cis-borylated cycloalkanes that are difficult to prepare by conventional methods.…”

Silylarenhydrierung – ein strategischer Ansatz für einen direkten Zugang zu silylierten gesättigten Carbo‐ und Heterocyclen

“…[18] Um zu zeigen, dass die silylierten Bausteine in der Synthese komplexer Strukturen verwendbar sind, wurde ein silyliertes Analogon des Muskelrelaxans Esperison (4) über eine Mannich-Reaktion des entschützten, silylierten Piperidins 3af hergestellt (Abbildung 3A). Als nächstes wurde die Kombination von Silylsubstituenten mit anderen FGs direkt am aromatischen Ring getestet.…”

“…Reaktive Alkoxy-(2g-i)u nd Abbildung S1) und 3p (Kristallstrukturanalyse) nachgewiesen. [18] Um zu zeigen, dass die silylierten Bausteine in der Synthese komplexer Strukturen verwendbar sind, wurde ein silyliertes Analogon des Muskelrelaxans Esperison (4) über eine Mannich-Reaktion des entschützten, silylierten Piperidins 3af hergestellt (Abbildung 3A). Weder während der basenvermittelten Entschützung noch während der säurekatalysierten Mannich-Reaktion wurde eine Desilylierung beobachtet.…”

Hydrogenation of (Hetero)aryl Boronate Esters with a Cyclic (Alkyl)(amino)carbene–Rhodium Complex: Direct Access to cis‐Substituted Borylated Cycloalkanes and Saturated Heterocycles

“…[8] Thec ontrol of stereoselectivity in the catalytic hydrogenation of substituted arenes is another major challenge,ascis and trans stereoisomers are usually formed. [10][11][12][13][14] This approach enables the hydrogenation of aryl and heteroaryl boronate esters with retention of the boronate ester functional group (Scheme 1b). [10][11][12][13][14] This approach enables the hydrogenation of aryl and heteroaryl boronate esters with retention of the boronate ester functional group (Scheme 1b).…”

“…[16,17] CAACs have found use as ancillary ligands in rhodium-catalyzed arene hydrogenations of aromatic ketones,phenols,fluoroarenes,and silylarenes. [11][12][13] We commenced our studies with the synthesis of the ortho-dimethyl-substituted CAAC-Rh complex ( Me CAAC)Rh(COD)Cl. [18] Ther elated aldiminium salt was deprotonated with lithium diisopropylamide (LDA), and then treated with [Rh(COD)Cl] 2 to afford the air-a nd moisturestable ( Me CAAC)Rh(COD)Cl complex in moderate yield (Scheme 2).…”