Toward the total synthesis of elisapterosin B: A Hg(OTf)(2)-promoted diastereoselective intramolecular Friedel-Crafts alkylation reaction

Crystal structures of two 1,2,3,4-tetra-hydro-naphthalenes obtained during efforts towards the total synthesis of elisabethin A

The two substituted 1,2,3,4-tetra-hydro-naphthalenes, methyl (R)-3-{(1R,4S)-6-meth-oxy-4,7-dimethyl-5,8-bis-[(triiso-propyl-sil-yl)-oxy]-1,2,3,4-tetra-hydro-naph-th-al-en-1-yl}butano-ate, C36H66O5Si2, (2), and methyl (E)-3-{(1R,4S)-8-hy-droxy-6-meth-oxy-4,7-dimethyl-5-[(triiso-propyl-sil-yl)-oxy]-1,2,3,4-tetra-hydro-naphthalen-1-yl}acrylate, C26H42O5Si, (8), crystallize in the Sohncke space groups P212121 and P21, respectively, with the absolute structure determined on the basis of anomalous dispersion effects. The configurations of the stereo centres in the 1,2,3,4-tetra-hydro-naphthalene moiety of (2) and (8) are the same, and the conformation of the non-aromatic part of the ring system is nearly identical. In the crystal of (2), weak non-classical C-H⋯O inter-actions consolidate the packing, whereas in (8), inter-molecular O-H⋯O hydrogen-bonding inter-actions of medium-to-weak strength direct the mol-ecules into Z-shaped strands extending parallel to [010].

Enantioselective Total Synthesis of Cerorubenic Acid-III via Type II [5+2] Cycloaddition Reaction

The first enantioselective total synthesis of cerorubenic acid-III is described in detail. Different strategies and attempts, based on a type II [5+2] cycloaddition reaction, leading to the bicyclo[4.4.1] ring system with a strained bridgehead double bond, are depicted. Furthermore, sodium naphthalenide was found to be efficient in the chemoselective reduction of 8-oxabicyclo[3.2.1]octene, with three transformations completed in one operation. An unusual S_N1 transannular cyclization reaction was applied to construct the synthetically challenging vinylcyclopropane moiety. This strategy enabled the total synthesis of cerorubenic acid-III in 19 steps.

Applications of Friedel-Crafts reactions in total synthesis of natural products

Over the years, Friedel-Crafts (FC) reactions have been acknowledged as the most useful and powerful synthetic tools for the construction of a special kind of carbon-carbon bond involving an aromatic moiety. Its stoichiometric and, more recently, its catalytic procedures have extensively been studied. This reaction in recent years has frequently been used as a key step (steps) in the total synthesis of natural products and targeted complex bioactive molecules. In this review, we try to underscore the applications of intermolecular and intramolecular FC reactions in the total syntheses of natural products and complex molecules, exhibiting diverse biological properties.

Intramolecular etherification and polyene cyclization of π-activated alcohols promoted by hot water

Hot water, acting as a mildly acidic catalyst, efficiently promoted intramolecular direct nucleophilic substitution reactions of unsaturated alcohols with heteroatom or carbon nucleophiles. In a mixed solvent of water and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), polyene cyclizations using allylic alcohols as initiators gave the desired cyclized products, and in neat HFIP, a tricyclization reaction gave a tetracyclic product in 51% chemical yield.

A heterogeneous mercury salt catalyst stabilized by m-carbaborane

A novel hetergeneous mercury salt catalyst stabilized by m-carbaborane can be used and reused for various chemical reactions without leaching the metal.

Enantioselective first total synthesis of eujavanoic acid B through organocatalyzed IMDA reaction

The first total synthesis of the polyketide eujavanoic acid B has been accomplished using 1,3-propane diol as the starting material and involving Maruoka asymmetric allylation, Julia olefination, HWE olefination and organocatalyzed IMDA reaction as the key steps.

Oxidation of 4-methoxyanilines to 1,4-benzoquinones using ceric ammonium nitrate (CAN)

Treatment of substituted 4-methoxyanilines with ceric ammonium nitrate in a 1:1 mixture of water and acetonitrile resulted in formation of 1,4-benzoquinones in acceptable yields.