Sigmatropic Rearrangements of Hypervalent‐Iodine‐Tethered Intermediates for the Synthesis of Biaryls

Abstract

Metal‐free dehydrogenative couplings of aryliodanes with phenols to afford 2‐hydroxy‐2′‐iodobiaryls have been developed. This reaction proceeds through ligand exchange on the hypervalent iodine atom followed by a [3,3] sigmatropic rearrangement and with complete regioselectivity. This coupling, in combination with in situ oxidation by mCPBA, enables the convenient conversion of iodoarenes into desirable biaryls. The obtained biaryls have convertible iodo and hydroxy groups in close proximity, and are thus synthetically useful, as exemplified by the controlled syntheses of π‐extended furans and a substituted [5]helicene. DFT calculations clearly revealed that the rearrangement is sigmatropic, with C−C bond formation and I−O bond cleavage proceeding in a concerted manner. Acetic acid, which was found to be the best solvent for this protocol, renders the iodine atom more cationic and thus accelerates the sigmatropic rearrangement.

Sulfonium-aided coupling of aromatic rings via sigmatropic rearrangement

“…After extensive screening, we found that 2-naphthols are suitable for the coupling and that treatment with 2-iodonaphthalene diacetate ( 43 ) in acetic acid yielded 2-hydroxy-2′-iodobinaphthyls 44 (Scheme 22 ). 82 ) Furthermore, iodoarene diacetate can be generated in situ and used without isolation; iodobenzene 45 was treated sequentially with m CPBA and 2-naphthol to afford biaryl 47 via 46 (Scheme 23 ).…”

Morita-Baylis-Hillman Reaction Inspired [3,3]-Rearrangement of Aryl Iodanes with α,β-Unsaturated Oxazolines

“…[5][6] The subsequent [3,3]-rearrangement occurs spontaneously leading to synthetically appealing ortho-functionalized aryl iodides. In the past three decades, an array of nucleophiles such as allyl/propargyl silanes, [7][8][9][10][11][12][13][14] carbonyl compounds, 15,16 phenols, 17 α-stannyl nitriles, [18][19][20][21] and enol silyl ethers 22 have been found to be suitable for the rearrangement process. Despite the progresses made, the reaction scope of carbonyl nucleophiles is limited to structurally de ned carbonyl compounds ( Fig.…”

Morita–Baylis–Hillman‐Type [3,3]‐Rearrangement: Switching fromZ‐ toE‐Selective α‐Arylation by New Rearrangement Partners

“…In the past few years,t he iodonium-and sulfonium-Claisen rearrangements have attracted great attention from synthetic community. [5,6] This type of rearrangement can be conducted by directly mixing readily available activated aryl iodanes and aryl sulfoxides with certain nucleophiles, [7][8][9][10][11] which allows in situ construction of ahighly reactive transient rearrangement precursor.Inthis context, we were interested in constructing the rearrangement precursor in as tepwise fashion which, we conceived, not only enhances the reaction efficiency but also render the reaction capable of adopting new intriguing functions. [12,13] Forexamples,with the stepwise strategy,w ew ere able to implement [3,3]-and [5,5]-rearrangement of aryl sulfoxides with alkyl nitriles and allyl nitriles,r espectively,v ia an assembly/deprotonation sequence.…”