First Total Syntheses of (±)-Annuionone B and (±)-Tanarifuranonol

Abstract

The intramolecular Diels-Alder reaction of o-quinol allyl ether was accomplished and subsequently applied to the first total syntheses of natural products annuionone B (1) and both the proposed and revised structure of tanarifuranonol, 4 and 17.

Enantioselective Construction of Bridged Multicyclic Skeletons: Intermolecular [2+2+2] Cycloaddition/Intramolecular Diels–Alder Reaction Cascade

“…The construction of the bridged multicyclic skeleton C, from phenol A, has been reported to proceed through oxidative dearomatization to give allyl cyclohexadienyl ether B , which then undergoes the IMDA reaction to yield C (Scheme ) 2. 3 This novel strategy was successfully applied to the synthesis of various complex natural products,3a,b,d,e but an asymmetric variant has not yet been developed because of the difficulty of the enantioselective dearomatization of phenols 4…”

Carbohydrate‐Templated Asymmetric Diels–Alder Reactions of Masked ortho‐Benzoquinones for the Synthesis of Chiral Bicyclo[2.2.2]oct‐5‐en‐2‐ones

“…After the mixture had been stirred for 6 h, the reaction flask was gradually warmed up and the mixture was heated to reflux for 16 h. The solution was cooled to room temperature, and the reaction was quenched by saturated aqueous NaHCO 3 . The whole mixture was extracted three times with ethyl acetate, and the combined organic layers were washed with brine, dried over anhydrous MgSO 4 , filtered, and [a] In 10 À1 deg cm 3 . Keywords: asymmetric synthesis · benzoquinones · bicyclic compounds · chiral auxiliaries · cycloaddition…”

“…[1] Highly reactive 6,6-dialkoxycyclohexa-2,4-dienones (namely, masked o-benzoquinones or MOBs) [2] and their orthoquinol variants, [3] which can be conveniently generated by oxidation of the corresponding 2-alkoxy-and 2-alkylphenols in an alcoholic solvent, are often used for synthesizing the bicyclo-[2.2.2]oct-5-en-2-ones in racemic form through in situ intra- [4] or intermolecular [5] Diels-Alder reactions with various dienophiles. [1] Highly reactive 6,6-dialkoxycyclohexa-2,4-dienones (namely, masked o-benzoquinones or MOBs) [2] and their orthoquinol variants, [3] which can be conveniently generated by oxidation of the corresponding 2-alkoxy-and 2-alkylphenols in an alcoholic solvent, are often used for synthesizing the bicyclo-[2.2.2]oct-5-en-2-ones in racemic form through in situ intra- [4] or intermolecular [5] Diels-Alder reactions with various dienophiles.…”

“…

Dedicated to Professor Chi-Huey Wong on the occasion of his 60th birthday Bicyclo[2.2.2]oct-5-en-2-ones have been widely applied in natural product synthesis for several decades. [1] Highly reactive 6,6-dialkoxycyclohexa-2,4-dienones (namely, masked o-benzoquinones or MOBs) [2] and their orthoquinol variants, [3] which can be conveniently generated by oxidation of the corresponding 2-alkoxy-and 2-alkylphenols in an alcoholic solvent, are often used for synthesizing the bicyclo-[2.2.2]oct-5-en-2-ones in racemic form through in situ intra- [4] or intermolecular [5] Diels-Alder reactions with various dienophiles. However, two major hurdles are frequently encountered in these studies: avoiding the self-dimerization of the MOBs [6] and preparing optically pure enantiomers.

…”

Carbohydrate‐Templated Asymmetric Diels–Alder Reactions of Masked ortho‐Benzoquinones for the Synthesis of Chiral Bicyclo[2.2.2]oct‐5‐en‐2‐ones

“…Bicyclo[2.2.2]oct‐5‐en‐2‐ones have been widely applied in natural product synthesis for several decades 1. Highly reactive 6,6‐dialkoxycyclohexa‐2,4‐dienones (namely, masked o ‐benzoquinones or MOBs)2 and their orthoquinol variants,3 which can be conveniently generated by oxidation of the corresponding 2‐alkoxy‐ and 2‐alkylphenols in an alcoholic solvent, are often used for synthesizing the bicyclo[2.2.2]oct‐5‐en‐2‐ones in racemic form through in situ intra‐4 or intermolecular5 Diels–Alder reactions with various dienophiles. However, two major hurdles are frequently encountered in these studies: avoiding the self‐dimerization of the MOBs6 and preparing optically pure enantiomers 7.…”