Radical substitution with azide: TMSN<sub>3</sub>–PhI(OAc)<sub>2</sub>as a substitute of IN<sub>3</sub>
作者:Christian Marcus Pedersen、Lavinia Georgeta Marinescu、Mikael Bols
DOI:10.1039/b500037h
日期:——
TMSN3 and PhI(OAc)2 were found to promote high-yield azide substitution of ethers, aldehydes and benzal acetals. The reaction is fast and occurs at zero to ambient temperature in acetonitrile. However, it is essential for the reaction that TMSN3 is added subsequent to the mixture of PhI(OAc)2 and the substrate. A primary deuterium kinetic isotope effect was found for the azidonation of benzyl ethers
作者:Hong-Fa Wang、Lin-Na Guo、Zhi-Bo Fan、Tian-Hua Tang、Weiwei Zi
DOI:10.1021/acs.orglett.1c00581
日期:2021.4.2
A Simple Route to .alpha.-Substituted-.beta.-Amino Ester Precursors of Carbapenem Antibiotics
作者:Patrick Perlmutter、Mark Tabone
DOI:10.1021/jo00125a043
日期:1995.10
A three-step process is presented for the preparation of alpha-substituted-beta-amino esters which can serve as precursors to a key intermediate in carbapenem synthesis. The pivotal reaction in this sequence involves a highly diastereoselective conjugate addition reaction. Two series of alkenoates bearing a stereogenic substituent attached to C2 were prepared and their conjugate addition reactions with benzylamine studied under several different sets of conditions. Conjugate addition of benzylamine to alkenoates 7a and 7d, in methanol at room temperature, gave adducts 8a and Sd with virtually complete anti-diastereoselectivity. These two beta-amino esters bear the correct relative stereochemistry and side chain to serve as precursors for carbapenem antibiotic synthetic intermediates. The role of the allylic substituents of the alkenoates 7a-e in determining the stereochemical outcome of these additions is discussed. These conjugate additions were explored further by the preparation and conjugate addition reactions of the alpha,beta-disubstituted alkenoates 15a and 15b. It was found that the presence of a beta-substituent led to a dramatic reduction in yield although the same anti-diastereoselectivity was maintained. The relative stereochemistry of the adducts was established by examination of the relevant coupling constants in the H-1 NMR spectra of their tetrahydro-1,3-oxazine derivatives.