Formation of the Main Cores Present in Natural Products by Tandem Additions

Abstract

A rapid route to 5,5- and 5,6- bicyclic systems is provided by an 1,3-alkyl-shift process mediated by a hypervalent iodine reagent on aromatics. The structures obtained contain several unsaturations with different behaviors and reactivities. Such diversity allows further elaborations for the rapid formation of compact systems present in a variety of natural products. The potential for further transformations has been demonstrated by performing a double Michael addition. This cyclization process is regio- and stereoselective due to the presence of a former benzylic substituent. Furthermore, an extension of this approach has been accomplished on indole derivatives.

Iodanes as multi-tools for the total synthesis of complex natural products

“…73 Several congeners of this class of molecules are known in the literature, e.g., fawcettimine. In 2015, we proposed a stereoselective route to their main bicyclic system 74 based on an oxidative 1,3-alkyl shift followed by a stereoselective poly-Michael addition in a cascade mediated by amines. Phenol 172 was converted upon treatment with PIDA to dienone 175 in 52% yield, and the subsequent addition of hydroxylamine led to the formation of bicyclic system 177 in 76% yield, Scheme 44.…”

Carbon–Phosphorus Bond Formation on Anilines Mediated by a Hypervalent Iodine Reagent

“…This oxidative process involves the in situ formation of a dienimine intermediate, which is trapped by a phosphorus nucleophile followed by a domino rearomatization. This transformation represents an aromatic variant of the Michaelis–Arbuzov reaction on an unactivated aromatic sp 2 center.…”

A Stereoselective Arylative-Cyclopropanation Process

“…Encouraged by this result, we investigated different halides as nucleofuges. These attempts have been performed on dienone 16, which represents a good Michael acceptor obtained by direct oxidation of halogenated phenols 15 in the presence of methanol and a hypervalent iodine reagent . Iodine and bromine provided slightly improved results, Scheme .…”