Umpolung Strategy for Arene C−H Etherification Leading to Functionalized Chromanes Enabled by I(III) N‐Ligated Hypervalent Iodine Reagents

Abstract

The direct formation of aryl CÀ O bonds via the intramolecular dehydrogenative coupling of a CÀ H bond and a pendant alcohol represents a powerful synthetic transformation. Herein, we report a method for intramolecular arene CÀ H etherification via an umpoled alcohol cyclization mediated by an I(III) N-HVI reagent. This approach provides access to functionalized chromane scaffolds from primary, secondary and tertiary alcohols via a cascade cyclization-iodonium salt formation, the latter providing a versatile functional handle for downstream derivatization. Computational studies support initial formation of an umpoled O-intermediate via I(III) ligand exchange, followed by competitive direct and spirocyclization/1,2-shift pathways.

I(III)-Mediated Arene C–H Amination Using (Hetero)Aryl Nucleophiles

“…In recent years, our laboratory has developed the I­(III) N -HVI reagent class ( 4 ); its members possess datively bound N-heterocyclic ligands (Scheme B, inset). − These reagents are bench stable, can be accessed in a single step from commercial materials, and are compatible with a broad range of heterocyclic ligands . Recent work from our group has demonstrated their utility in “heterocyclic group transfer” (HGT) reactions with olefins as a novel means of accessing complex N -alkylpyridinium salts .…”

Updates on hypervalent-iodine reagents: metal-free functionalisation of alkenes, alkynes and heterocycles

“…The Wengryniuka group in 2021, reported an efficient method that provides access to functionalised chromanes ( 78 ) from primary, secondary, and tertiary alcohols via cyclisation followed by iodonium salt formation (Scheme 49). 106…”

“…105 As per the suggested mechanism, initially, the hypervalent species The Wengryniuka group in 2021, reported an efficient method that provides access to functionalised chromanes (78) from primary, secondary, and tertiary alcohols via cyclisation followed by iodonium salt formation (Scheme 49). 106 The He group reported an effective method for the aminolactonisation of unactivated alkenes (79) via aryl-iodine catalysis, in which diverse amino lactones (80) are constructed in a short time using HNTs 2 as the compatible nitrogen source. The methodology also demonstrated some asymmetric aminolactonisation using a chiral iodoarene precatalyst (Scheme 50).…”