Mechanism and Application of Baker–Venkataraman O→C Acyl Migration Reactions

Abstract

This literature review focuses on the O→C acyl migration of aryl esters to yield the corresponding 1,3-dicarbonyl products-a reaction known as the Baker-Venkataraman rearrangement-and outlines their subsequent transformations. The purpose of the review is to highlight the utility of the rearrangement which provides a key step in the synthesis of various heterocyclic motifs. The scope of the BakerVenkataraman rearrangement is illustrated by way of numerous examples of its application, and in doing so, the review contains over 100 references and covers just over 100 years of the literature, from the first report of the rearrangement by Auwers in 1910 up to more recent examples in the past few years.

Accessing 7‐Azaaurones of Controllable E and Z Configurations from 8‐Azaflavones via a Rearrangement‐Acylation‐Photoisomerization Sequence

“…Synthesis of 3‐halogenated 8‐azaflavones . In flavone synthesis, the Baker‐Venkataraman methodology refers to the C‐benzoylation of 2’‐hydroxyacetophenone (via intramolecular acyl migration of intermediate O‐acylation products), [15] followed by dehydrative cyclization of the resulting diketone into flavone. Application of this methodology to 8‐azaflavones relies on the availability of 3‐acetyl‐2‐pyridones.…”

DBU-promoted carboxylative cyclization of o-hydroxy- and o-acetamidoacetophenone

“…The reaction can evolve along two pathways: in path A , deprotonation of o -acetamidoacetophenone by DBU gives enolate I , which undergoes an acyl migration from nitrogen to carbon [25–26] similar to the Baker–Venkataraman O to C acyl migration [27]. After a proton shift from the enol to nitrogen, the resultant intermediate III is carboxylated with carbon dioxide in the presence of DBU to afford intermediate IV , which subsequently undergoes a cyclization reaction to give V .…”

Flavones and Related Compounds: Synthesis and Biological Activity

“…However, the conventional method could not produce large yields of flavones [ 91 ]. Cramer and Elschnig discovered that the best catalyst is sodium ethoxide [ 92 ].…”

“…According to the mechanism, this method starts with an intramolecular Claisen condensation between acetophenone and an ester group grafted in ortho position on the aromatic ring (an o-acyloxyacetophenone 48), which can also be interpreted as acyl group transfer. This is followed by cyclocondensation in acidic conditions via a 2-hydroxyflavanone intermediate (53) (Scheme 15) [3,91]. Verkataraman first used this method to obtain α-naphtoflavone from 2-acetyl-1-naphthyl benzoate via heating with sodium benzoate and benzoic anhydride [88,89].…”