Recent Advances in the Benzannulation of Substituted 3‐Alkoxycarbonyl‐3,5‐hexadienoic Acids and 3‐Alkoxycarbonylhex‐3‐en‐5‐ynoic Acids to Polysubstituted Aromatics

Abstract

The benzannulation reactions of substituted 3-alkoxycarbonyl-3,5-hexadienoic and 3-alkoxycarbonylhex-3-en-5-ynoic acids offer a straightforward access to various polysubstituted aromatic compounds. The process is very flexible, and can be applied to the regiospecific preparation of oligoaryls, naphthalenes, ring-fused heterocycles, chiral tetrahydronaphthalenes, C-aryl-glycosides and many natural products of different structure. In this Concept article, we highlight the potential of this annulation reaction by illustration of our recent contribution to this field, as well as the studies previous reported by others.

One-Pot Synthesis of 3,5-Disubstituted and Polysubstituted Phenols from Acyclic Precursors

“…Among the substituted phenols, regiospecific synthesis of 3,5-disubstituted phenols is a challenging task because electrophilic aromatic substitution of phenols is unfavorable at the meta (3 and 5) positions . Alternative synthetic methods using nonaromatic precursors have been developed, which include benzannulations of vinylketenes, carbenes, or alkyenes, carbonyl insertion of vinylcyclopropenes, Diels–Alder-based cycloaromatization of alkynes, [3 + 3] cyclocondensations involving 1,3-dicarbonyl compounds, dienone–phenol rearrangements, dehydrogenative aromatization of cyclohexenones, and eliminative aromatization of cyclohexenones . However, not all of these methods are regiospecific for 3,5-disubstituted phenols.…”

A new and informative [a,b,c,d] nomenclature for one-pot multistep transformations: a simple tool to measure synthetic efficiency

“…2-Indolyl-C-glycosides, 44 a subset of C-aryl glycosides form an important class of biologically active compounds having a heteroaryl aglycon ( Fig. 6 ).…”

Recent developments of ketene dithioacetal chemistry

“…The regiospecific construction of six-membered carbo-and heterocyclic systems represents a major challenge in organic synthesis. [185][186][187] In 2005, we reported the first example for the regiospecific synthesis of poly-substituted phenols 326 in a single step based on a [5C + 1C] benzannulation strategy starting from the easily available five-carbon 1,5-bielectrophiles, alkenoyl ketene dithioacetals 325 (Scheme 87). 188 The reaction of 325 with nitroalkanes in the presence of DBU (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) at room temperature afforded cyclohexenones 328 in high yields.…”