Michael Addition Reaction Catalyzed by Imidazolium Chloride to Protect Amino Groups and Construct Medium Ring Heterocycles

Enantioselective Synthesis of Chiral 1,5-Benzodiazepin-2-ones by Pd-Catalyzed Asymmetric Hydrogenation and Reductive Amination

The enantioselective synthesis of chiral 4-substituted 4,5-dihydro-1H-[1,5]benzodiazepin-2(3H)-ones via asymmetric hydrogenation catalyzed by the Pd/f-spiroPhos complex in the presence of hydrochloric acid as an additive has been developed, achieving excellent enantioselectivities and high turnover numbers, up to 99% ee and TON = 4600. More significantly, the asymmetric reductive amination of β-keto esters with 1,2-phenylenediamine has also been successfully realized to afford chiral 4-substituted 4,5-dihydro-1H-[1,5]benzodiazepin-2(3H)-ones with comparable enantioselectivities of up to 99% ee.

Hydroxyl carboxylate anion catalyzed depolymerization of biopolyesters and transformation to chemicals

Upcycling biopolyesters (e.g., polyglycolic acid, PGA) into chemicals is an interesting and challenging topic. Herein, we report a novel protocol to upgrade biopolyesters derived from hydroxyl carboxylic acids over ionic liquids with a hydroxyl carboxylate anion (e.g., glycolate, lactate) into various chemicals under metal-free conditions. It is found that as hydrogen-bond donors and acceptors, hydroxyl carboxylate anions can readily activate the ester group via hydrogen bonding and decompose biopolyesters via autocatalyzed-transesterification to form hydroxyl carboxylate anion-based intermediates. These intermediates can react with various nucleophiles (e.g. H2O, methanol, amines and hydrazine) to access the corresponding acids, esters and amides under mild conditions (e.g., 40 °C). For example, 1-ethyl-3-methylimidazolium glycolate can achieve complete transformation of PGA into various chemicals such as glycolic acid, alkyl glycolates, 2-hydroxy amides, 2-(hydroxymethyl)benzimidazole, and 1,3-benzothiazol-2-ylmethanol in excellent yields via hydrolysis, alcoholysis and aminolysis, respectively. This protocol is simple, green, and highly efficient, which opens a novel way to upcycle biopolyesters to useful chemicals.