Synthesis of Peptides and Pyrazines from β‐Amino Alcohols through Extrusion of H₂ Catalyzed by Ruthenium Pincer Complexes: Ligand‐Controlled Selectivity

Rechargeable Hydrogen Storage System Based on the Dehydrogenative Coupling of Ethylenediamine with Ethanol

“…Based on our previous research on dehydrogenation reactions [14][15][16]20] and the above results,asimplified mechanism for the dehydrogenative amidation of ED and ethanol is shown in Scheme 1. Dehydrogenation of ethanol forms acetaldehyde as an intermediate,w hich reacts with one amine group of ED to form ah emiaminal intermediate.T he latter undergoes competitive elimination of water to produce N-ethylidenethane-1,2-diamine [20] and elimination of hydrogen to form N-(2-aminoethyl)acetamide.R eaction of N-(2aminoethyl)acetamide with another molecule of acetaldehyde and release of one molecule of hydrogen leads to N,N'diacetylethylenediamine as the product.…”

“…[14,15] In addition, amides can be hydrogenated to the corresponding amines and alcohols under mild hydrogen pressure,c atalyzed by the same type of catalysts. [14,15] In addition, amides can be hydrogenated to the corresponding amines and alcohols under mild hydrogen pressure,c atalyzed by the same type of catalysts.…”

Transition‐Metal‐Catalyzed Hydrogen‐Transfer Annulations: Access to Heterocyclic Scaffolds

“…Figure 3). [9] Inter-a nd intramolecular hydrogen-transfer annulations of alcohols with various coupling partners enable the formation of functionalized saturated and aromatic heterocyclic compounds.T his methodology has provided direct and rapid access to avariety of heterocyclic frameworks.…”

“…[15] Recently,K rische and co-workers reported am ethod for the synthesis of C2-substituted pyrrolidines (14)t hrough hydrogen-transfer hydroaminoalkylation of amino alcohols with dienes (Scheme 2). Thereaction proceeds with complete branch selectivity and good to excellent levels of antidiastereoselectivity.O ptimization of the reaction conditions and catalyst identified in situ generated catalysts,d erived from [HClRu(CO)(PPh 3 ) 3 ]and various phosphine ligands,for delivery of 2-substituted pyrrolidines in high yield and with maximum diastereoselectivity.Mechanistically,alcohol dehydrogenation triggers generation of an electrophilic imine,3,4-dihydro-2H-pyrrole (9), and ruthenium hydride.T he latter undergoes hydrometalation with the diene to form the nucleophilically less-stable disubstituted p-allylruthenium complex 10.T he complex 10 undergoes reversible isomerization to form the more-stable isomeric monosubstituted pallylruthenium complex 11 which is involved in imine addition via the (E)-s-allylruthenium haptomer to afford C2-substituted pyrrolidines.T he reversibility of the hydrometallation step was studied for the coupling reaction of ad euterated amino alcohol [HOCD 2 (CH 2 ) 3 NH 2 ]w ith butadiene under standard reaction conditions.S ignificantly,d euterium incorporation was observed at all vinylic positions,a llyl positions, and in the methyl group (R = H) of the product, thus confirming the reversibility of the hydrometalation step. Complete retention of deuterium (> 95) at the methine position adjacent to the nitrogen atom confirmed the nonreversibility of alcohol dehydrogenation for imine formation.…”

Highly efficient synthesis of 2,5-disubstituted pyrazines from (Z)-β-haloenol acetates

“…10 Consequently, much effort has been made to design methods for the preparation of pyrazines. 13 Recently, alternative methods have been reported for the synthesis of pyrazine derivatives, including the reaction of epoxides with 1,2-amino alcohols, 14 dimerization of azomethine ylides, 15 the Ru-catalyzed dehydrogenative coupling of β-amino alcohol 16 and YbCl 3 -catalyzed one-pot pyrazine formation. 12 Besides, synthesis of pyrazines from α-halo ketones has a long history.…”