Strategies were sought to effect cyclizations of oligo(m-phenylene ethynylene) by exploiting pseudo-high dilution effects on polymer supports. Using Pd/Cu-catalyzed coupling protocols, Merrifield's resin (1% crosslinked chloromethylated polystyrene) proved inadequate for site isolation; inter-site couplings ensued on the flexible support. Conversely, use of the Argopore resin, a more highly crosslinked polystyrene, inhibited inter-site interactions, and no identifiable final product could be separated from the resin. Spectroscopic and mass spectrometric methods indicated that the product from the Argopore resin might be a threaded catenane. (C) 2001 Elsevier Science Ltd. All rights reserved.
Reaction between nitrogen‐centered radicals and unsaturated C−C bonds is an effective synthetic strategy for the construction of nitrogen‐containing molecules. Although the reactions between nitrogen‐centered radicals and alkenes have been studied extensively, their counterpart reactions with alkynes are extremely rare. Herein, the first example of reactions between azidylradicals and alkynes is described
An efficient method for stereoselective nitroaminoxylation of alkyne has been reported. The reaction enjoys a broad substrate scope, good functional group tolerance, and high yields. Synthetically useful α-nitroketones can be accessed through these products in a single step.
Easy access to a wide range of structurally diverse stapled peptides is crucial for the development of inhibitors of protein‐protein interactions. Herein, we report bis‐functional hypervalent iodine reagents for two‐component cysteine‐cysteine and cysteine‐lysine stapling yielding structurally diverse thioalkyne linkers. This stapling method works with unprotected natural amino acid residues and does
A protecting group Ph2P(O) for terminal ethyne was newly developed. This protecting group can be introduced readily to terminal ethyne by CuI-catalyzed phosphination and subsequent oxidation with H2O2. Ph2P(O)-protected ethynes remained intact in Sonogashira coupling, and their high polarity enabled easy separation of the desired coupling product from by-products. By treatment with t-BuOK, Ph2P(O)-protected
Synthesis of chiral 1,3-bis(1-(diarylphosphoryl)ethyl)-benzenes via Ir-catalyzed double asymmetric hydrogenation of bis(diarylvinylphosphine oxides)
作者:Xu Liu、ZhaoBin Han、Zheng Wang、KuiLing Ding
DOI:10.1007/s11426-014-5134-7
日期:2014.8
A class of chiral 1,3-bis(diarylphosphinoethyl)benzenes, which are key intermediates for the synthesis of PCP-type chiral pincer ligands, were prepared in high diastereomeric ratios and excellent ee values via double asymmetric hydrogenation of the corresponding bis(diarylvinylphosphine oxide) substrates using a SpinPhox/Ir(I) complex as the catalyst. The hydrogenation product 5a was readily transformed