438239-49-7Relevant academic research and scientific papers
Auxiliary controlled enantioselective synthesis of 3-aryl-prolines
Laabs, Stephan,Münch, Winfried,Bats, Jan W,Nubbemeyer, Udo
, p. 1317 - 1334 (2002)
The synthesis of optically active cis 3-aryl proline derivatives was achieved in a five-step sequence involving an enantioselective aza-Claisen rearrangement as the key step. Initially, suitable cinnamyl amines were generated via a Pd(0) catalyzed amination of the corresponding N-allyl mesylates using optically active proline derivatives as chiral auxiliaries. The zwitterionic aza-Claisen rearrangement with azidoacetyl fluoride gave the corresponding α-azido-γ,δ-unsaturated amides with a complete simple and a moderate to high induced diastereoselectivity. The so formed unsaturated azides were subjected to a reductive cyclization developed by Evans and Sabol to generate the 2,3-cis-3-arylproline amides with high yields. The absolute configuration of one representative compound was proven by X-ray analysis. The removal of the auxiliary was difficult but succeeded at the stage of the unsaturated amide by treatment with acid without decrease of the diastereoselectivity. The so obtained 3-arylprolines are useful key fragments in biologically interesting (cyclo-) peptides and peptidomimetics.
Highly chemoselective reductive amination of carbonyl compounds promoted by InCl3/Et3SiH/MeOH system
Lee, On-Yi,Law, Ka-Lun,Ho, Chun-Yu,Yang, Dan
experimental part, p. 8829 - 8837 (2009/04/05)
(Chemical Equation Presented) A new strategy has been developed for reductive amination of aldehydes and ketones with the InCV Et 3SiH/MeOH system, which is a nontoxic system with highly chemoselective and nonwater sensitive properties. The methodology can be applied to a variety of cyclic, acyclic, aromatic, and aliphatic amines. Functionalities including ester, hydroxyl, carboxylic acid, and olefin are found to be stable under our conditions. The reaction shows a first-order kinetics profile with respect to both InCl3 and Et3SiH. Spectroscopic techniques such as NMR and ESI-MS have been employed to probe the active and resulting species arising from InCl3 and Et3SiH in MeOH, which are important in deriving a mechanistic proposal. In the ESI-MS studies, we have first discovered the existence of stable methanol-coordinated indium(III) species which are presumably responsible for the gentle generation of indium hydride at room temperature. The solvent attribution was crucial in tuning the reactivity of [In-H] species, leading to the establishment of mild reaction conditions. The system is superior in flexible tuning of hydride reactivity, resulting in the system being highly chemoselective.
