Phenazinium Salt-Catalyzed Aerobic Oxidative Amidation of Aromatic Aldehydes
作者:Dasheng Leow
DOI:10.1021/ol5029354
日期:2014.11.7
Amides are prevalent in organic synthesis. Developing an efficientsynthesis that avoids expensive oxidants and heating is highly desirable. Here the oxidativeamidation of aromaticaldehydes is reported using an inexpensive metal-free visible light photocatalyst, phenazine ethosulfate, at low catalytic loading (1–2 mol %). The reaction proceeds at ambient temperature and uses air as the sole oxidant
Phenylsilane as been reassed as useful coupling reagent for amides synthesis. Peptides and Weinreb amides are easily obtained under mild conditions in absence of epimzerization even with challenging substrates such as phenylglycine. Further investigation regarding the reactivity of stable acetoxysilanes supported phenylpolyacyloxysilane as key intermediate.
We report that the nucleophilic acyl substitution reaction of aliphatic and (hetero)aromaticamides by organolithium reagents proceeds quickly (20 s reaction time), efficiently, and chemoselectively with a broad substrate scope in the environmentally responsible cyclopentyl methyl ether, at ambient temperature and under air, to provide ketones in up to 93 % yield with an effective suppression of the
Reactions of Hexadehydro-Diels–Alder (HDDA)-Derived Benzynes with Thioamides: Synthesis of Dihydrobenzothiazino-Heterocyclics
作者:Vignesh Palani、Junhua Chen、Thomas R. Hoye
DOI:10.1021/acs.orglett.6b03199
日期:2016.12.16
Reaction of thioamides (e.g., II) with benzynes generated by the hexadehydro-Diels–Alder (HDDA) cycloisomerization (e.g., I) produces dihydrobenzothiazines (e.g., III). It is postulated that the reaction proceeds via benzothietene (cf. IV) and o-thiolatoaryliminium (cf. V) intermediates and that the latter undergoes intramolecular 1,3-hydrogen atom migration to produce the penultimate isomeric iminium
oxidative coupling of aromatic or aliphatic aldehydes with amines mediated by riboflavin tetraacetate (RFTA), an inexpensive organic photocatalyst, and visiblelight using oxygen as the sole oxidant. The method is based on the oxidative power of an excited flavin catalyst and the relatively low oxidation potential of the hemiaminal formed by amine to aldehyde addition.