Synthesis of Di- and Tri-Substituted Imidazole-4-carboxylates via PBu3-Mediated [3 + 2] Cycloaddition
摘要:
Some new di- and trisubstituted imidazole-4-carboxylates were prepared from amidoacetic acids 3 in the present report. The key step to establish such imidazole-4-carboxylates stemmed from the PBu3-mediated [3+2] cycloaddition between in situ-generated 2-oxazolinone 4 and ethyl cyanoformate6. Our results indicated that trisubstituted imidazoles 7-20 were afforded in better yields than those of disubstituted imidazoles 21-27. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications (R) to view the free supplemental file.
Preparation and spectra of para-substituted 2,5-diphenyloxazoles
作者:A.T. Balaban、L. Bîrlǎdeanu、I. Bally、P.T. Frangopol、M. Mocanu、Z. Simon
DOI:10.1016/0040-4020(63)85035-8
日期:1963.1
acid azlactone with halobenzenes, toluene, and anisole, followed by treatment with phosphorus oxychloride. Grignard and Ullmann reactions of p-halo-substituted 2,5-diaryloxazoles are described. Absorptionspectra of these compounds are discussed and the pronounced bathochromic effect of coupled donor and acceptor groups in both para positions is accounted for by a simple MO treatment.
Catalytic Asymmetric Synthesis of <i>anti</i>-α,β-Diamino Acid Derivatives
作者:Sanae Izumi、Yusuke Kobayashi、Yoshiji Takemoto
DOI:10.1021/acs.orglett.5b03666
日期:2016.2.19
A novel approach to chiral anti-α,β-diamino acid derivatives through tandem orthogonal organocatalysis has been developed. Chiral phosphoric acid catalysts control the chemo-, regio-, and stereoselective addition of hydroxylamines to alkylideneoxazolones, while a phosphine catalyst promotes the isomerization of Z- alkylideneoxazolones to the more reactive E- alkylideneoxazolones.
New 13-vinyl derivatives of berberine: synthesis and characterization
作者:Oleg D. Demekhin、Oleg N. Burov、Mikhail E. Kletskii、Anton V. Lisovin、Sergey V. Kurbatov、Elena A. Bereznyak、Alena V. Trishina
DOI:10.1007/s10593-022-03067-w
日期:2022.2
13-vinylberberines were stable in their reduced form due to significant intramolecular electron density transfer from berberine ringsystem to the vinyl moiety bearing electron-withdrawing groups. It was demonstrated that berberine derivatives may exist not only in ion pair form consisting of organic cation and inorganic anion, but also as zwitterionic structures featuring significant intramolecular charge transfer
Pd-catalyzed C–N bond cleavage strategy for the cycloaddition of pyrrolidines with azlactones or butenolides to construct the azepines. Leverage of the readily accessible 3-alkylidenepyrrolidine can serve as an effective precursor for zwitterionic salts. The in situ formation of an allyl-palladium intermediate through the cleavage of inert, cyclic C–N bonds leads to a cascade [5 + 2] cycloaddition, which allows
Enantioselective Synthesis of Axially Chiral Diaryl Ethers through Chiral Phosphoric Acid-Catalyzed Desymmetric Acylation with Azlactones
作者:Jiawei Xu、Wei Lin、Hanliang Zheng、Xin Li
DOI:10.1021/acscatal.4c01489
日期:2024.5.3
C–O axially chiral diaryl ethers play important roles in natural products and bioactive molecules, but because of the low rotational barrier and strict steric hindrance requirements, the catalytic asymmetric construction of axially chiral diaryl ethers still remains a challenge. Herein, we devised a strategy employing achiral azlactone for the desymmetrization of prochiral diamines under the catalysis