Transesterification for synthesis of carboxylates using aldehydes as acyl donors via C-H and C-O bond activations
A new type of transesterification between aryl, heteroaryl, alkyl N-heteroarene-2-carboxylates and various aldehydes by C-H and C-O bond activations has been developed for the synthesis of versatile carboxylates. A possible mechanism containing oxidative addition of acyl-O bond in parent ester and radical cleavage of sp2 C-H bond in aldehyde is proposed.
Bao, Yong-Sheng,Chen, Chao-Yue,Huang, Zhi-Zhen
p. 8344 - 8349,6
(2020/10/15)
Synthesis of 2,3-disubstituted-6-chromones of potential medicinal interest
The title compounds (12-19) have been synthesized by the condensation of 2,3-disubstituted-6-chromones (8-11) with hydrazine hydrate in the presence of formic or acetic acid.Their structures have been elucidated on the basis o
Singh, O. V.,Sangeeta,Khanna, M. S.,Garg, C. P.,Kapoor, R. P.,et al.
p. 1241 - 1248
(2007/10/02)
Synthesis of 6-Acetyl-3-alkyl-2-phenyl-chromen-4-ones by Phasetransfer Catalysed Baker-Venkataraman Reaction
Three of the five partial steps of the Baker-Venkataramansynthesis of flavones (scheme 1) can be flavoured by PTC conditions.In the intermolecular O-acylations of the 4-hydroxyacetophenone 1 (A) and the 5-acetyl-2-hydroxy-acylophenones 3 (C), respectively, the nucleophilicity of the phenolat anions is increased by the PT catalysator.The steric and electronic effects of the substituents in the 5-acetyl-2-benzoyloxy-acylophenones 4 cause the formation of the 6-acetyl-flavones 6 in the phasetransfer catalysed Baker-Venkataraman rearrangement (D) in one step and in good yields.The over-all yields of the 1 -> 6 reactions are not higher than 30percent because of the limiting step (B).This Fries rearrangement of 4-acyloxy-acetophenones 2 affords only 32-62percent of 3 under drastically enhanced conditions.
Henning, H.-G.,Schwabe, B.,Kernchen, F.,Westphal, G.
p. 491 - 501
(2007/10/02)
Phasentransfer-katalysierte O-Acylierung von 4-Acetyl-phenol