Iodine‐Catalyzed Claisen‐Rearrangements of Allyl Aryl Ethers and Subsequent Iodocyclizations

Abstract

Iodine can be considered as the simplest halogenbond donor. Previous investigations have revealed its remarkable catalytic effect in various reactions. The catalytic activity of iodine can often even compete with that of traditional Lewis acids. So far, iodine was typically used to activate carbonyl derivatives like Michael acceptors. We now demonstrate that iodine can also be used to activate allyl aryl ethers in Claisen rearrangements. The formed ortho-allylic phenols rapidly undergo iodocyclizations to afford dihydrobenzofurans, which are important building blocks for medicinal applications. A comparison with different catalysts further highlights the potential of iodine catalysis for this reaction. Computational and mechanistic investigations provide deeper insights into the underlying non-covalent interactions and their role for the catalysis.

Direct π‐Activation vs. O‐Activation in Halogen‐Bonding Catalysis

“…We finally evaluated the performance of the B2PLYP-D3 double hybrid functional, as it has been reported on numerous occasions for studying iodinecatalyzed processes. [13,14,33] The activation barrier of the uncatalyzed process was almost identical to the other functionals and in line with the reported barrier computed using the aug-cc-PVTZ basis set (77 kJ mol À 1 ). [32] The barriers of the catalyzed processes very closely followed the results using MN15, with the clear π-vs. O-activation preference remaining unchanged.…”

“…The MN15 functional did provide a slightly different behavior, with an observable barrier‐lowering effect for the O ‐activation, but again the preference for π‐activation remained clear. We finally evaluated the performance of the B2PLYP‐D3 double hybrid functional, as it has been reported on numerous occasions for studying iodine‐catalyzed processes [13, 14, 33] . The activation barrier of the uncatalyzed process was almost identical to the other functionals and in line with the reported barrier computed using the aug‐cc‐PVTZ basis set (77 kJ mol −1 ) [32] .…”

Direct π-Activation vs. O-Activation in Halogen Bonding Catalysis

“…We finally evaluated the performance B2PLYP-D3 double hybrid functional, as it has been reported on numerous occasions for the study of iodine-catalysed processes. [13,14,33] The barrier of activation of the uncatalyzed process was found to be almost identical to the other functionals, and in line with the reported barrier computed using the aug-cc-PVTZ basis set (77 kJ/mol). [32] The barriers of the catalyzed processes very closely followed the results using MN15, with the clear π-vs O-activation preference remaining unchanged.…”

Iodine-Promoted Disproportionate Coupling Reaction of Arylsulfonyl Hydrazides: A Simple and Green Access to Thiosulfonates

“…Iodine is often used in organic synthesis due to its stable chemical properties and easy availability. [27][28][29] As a non-toxic and green renewable resource, water has become an excellent reaction medium for organic conversion. [30][31][32] Therefore, based on our previous research on the synthesis of thiosulfonate by…”

“…Iodine is often used in organic synthesis due to its stable chemical properties and easy availability. [27][28][29] As a non-toxic and green renewable resource, water has become an excellent reaction medium for organic conversion. [30][31][32] Therefore, based on our previous research on the synthesis of thiosulfonate by using aromatic sodium sulfinate as a raw material and Lewis acid as an accelerator, 33 herein, a synthetic strategy for constructing thiosulfonate compounds through a single component cross oxidative coupling reaction was designed by using aromatic sulfonyl hydrazine as the single sulfur source with iodine as the promoter (Scheme 1, this work).…”