Can One Predict Changes from S<sub>N</sub>1 to S<sub>N</sub>2 Mechanisms?
作者:Thanh Binh Phan、Christoph Nolte、Shinjiro Kobayashi、Armin R. Ofial、Herbert Mayr
DOI:10.1021/ja903207b
日期:2009.8.19
lifetimes of benzhydrylium ions in the presence of amines and DMSO. The changefrom S(N)1 to S(N)2 mechanism occurred close to the point where the calculated rate constant for the collapse of the benzhydrylium ions with the amines just reaches the vibrational limit; that is, the concerted S(N)2 mechanism was only followed when it was enforced by the lifetime of the intermediate. The nucleophile-specific
traditional C −C cross‐coupling reactions they have been rarely used and Pd catalysts usually give a superior performance. Herein we report that in situ formed gold metal nanoparticles are highly active catalysts for the crosscoupling of allylstannanes and activated alkylbromides to form C −C bonds. Turnover numbers up to 29 000 could be achieved in the presence of active carbon as solidsupport, which allowed
A compound of the formula:
wherein R1 is H or a substituent; m is 1-3; Ar is an aromatic group which may be substituted; X is a bond or a divalent straight-chain group having 1-6 atoms which may be substituted; Y is —S—, —O—, or —N(R2— (R2 is H or a substituent group), Z is —N═ or —C(R3)═ (R3 is H or a hydrocarbon group), ring A is a benzene ring; ring B is a 5- to 7-membered ring which may be substituted, or a salt thereof is useful for eliciting a prostaglandin I2 receptor agonistic effect.
A process for producing an insulin type peptide, for example a relaxin, involving oxidizing a methionine residue on a B-chain having cysteine residues and combining the B chain with an A chain having cysteine residues to form a peptide having intermolecular disulphide links and biological activity. Novel synthetic relaxin 1 and methionine oxidized relaxins and Met(O) B-chains having enhanced solubility are disclosed.
Chiral Bifunctional Phosphine-Carboxylate Ligands for Palladium(0)-Catalyzed Enantioselective C−H Arylation
作者:Lei Yang、Markus Neuburger、Olivier Baudoin
DOI:10.1002/anie.201712061
日期:2018.1.26
Previous enantioselective Pd0‐catalyzed C−H activation reactions proceeding via the concerted metalation‐deprotonation mechanism employed either a chiral ancillary ligand, a chiral base, or a bimolecular mixture thereof. This study describes the development of new chiral bifunctional ligands based on a binaphthyl scaffold which incorporates both a phosphine and a carboxylic acid moiety. The optimal