An efficient synthesis of 2,5-disubstitutedoxazolesvia Co(III) catalysis is described herein. The synthesis is achieved under mild conditions through [3+2] cycloaddition of N-pivaloyloxyamides and alkynes. The reaction operates through an internal oxidation pathway and features a very broad substrate scope. The one-step synthesis of natural products such as texamine and balsoxin has been demonstrated
A practicalone‐pot protocol for the synthesis of 2,5‐disubstitutedoxazoles from 1‐aryl‐2‐nitroethanones was reported. In the presence of iron/AcOH in acetonitrile, the reaction of 1‐aryl‐2‐nitroethanones with trimethyl orthoacetate or trimethyl orthobenzoate delivered the corresponding 2,5‐disubstitutedoxazoles in moderate to good yields.
Indium-mediated one-pot synthesis of benzoxazoles or oxazoles from 2-nitrophenols or 1-aryl-2-nitroethanones
作者:Jung June Lee、Jihye Kim、Young Moo Jun、Byung Min Lee、Byeong Hyo Kim
DOI:10.1016/j.tet.2009.08.059
日期:2009.10
One-pot reduction-triggered heterocyclizations from 2-nitrophenols to benzoxazoles and from 1-aryl-2-nitroethanones to oxazoles were investigated. In the presence of indium/AcOH in benzene at reflux, 2-nitrophenols and R-C(OMe)(3) (R=H, Me, Ph) produced excellent yields of corresponding benzoxazoles within an hour. Similarly, 1-aryl-2-nitroethanones and Ph-C(OMe)(3) in the presence of indiurn/AcOH in acetonitrile transformed into the corresponding oxazoles with good yields. (c) 2009 Elsevier Ltd. All rights reserved.
Metal-Free sp3 C–H Functionalization: PABS/I2-Promoted Synthesis of Polysubstituted Oxazole Derivatives from Arylethanones and 2-Amino-2-alkyl/arylacetic Acid
nonmetal-catalyzed process for the synthesis of polysubstituted oxazoles from inexpensive and readily available α-amino acids and methyl ketones is established. This reaction is proposed to achieve oxidative cleavage of C(sp3 )–Hbonds, followed by decarboxylation and annulation. The mild reaction conditions employed in both cases enable the tolerance of a wide range of functional groups as well as high reaction