Cyclic Homo- and Heterohalogen Di-λ³-diarylhalonium Structures

Abstract

In the context of the ever-growing interest in the cyclic diaryliodonium salts, this work presents synthetic design principles for a new family of structures with two hypervalent halogens in the ring. The smallest bis-phenylene derivative, [(C6H4)2I2]2+, was prepared through oxidative dimerization of a precursor bearing the ortho-disposed iodine and trifluoroborate groups. We also report, for the first time, the formation of cycles containing two different halogen atoms. These present two phenylenes linked by hetero-(I/Br) or -(I/Cl) halogen pairs. This approach was also extended to the cyclic bis-naphthylene derivative [(C10H6)2I2]2+. The structures of these bis-halogen(III) rings were further assessed through X-ray analysis. The simplest cyclic phenylene bis-iodine(III) derivative features the interplanar angle of ∼120°, while a smaller angle of ∼103° was found for the analogous naphthylene-based salt. All dications form dimeric pairs through a combination of π–π and C–H/π interactions. As the largest member of the family, a bis-I(III)-macrocycle was also assembled using the quasi-planar xanthene backbone. Its geometry enables the two iodine(III) centers to be bridged intramolecularly by two bidentate triflate anions. In a preliminary manner, the interaction of the phenylene- and naphthalene-based bis-iodine(III) dications with a new family of rigid bidentate bis-pyridine ligands was studied in solution and the solid state, with an X-ray structure showing the chelating donor bonding to just one of the two iodine centers.

Copper-catalyzed nitration of electron-deficient BN-naphthalene

“…In comparison between 4c and 6c , the introduction of a nitro group into the diiodo-ABN system makes no significant change in the structural metric parameters of 6c relative to 4c , and similar results are also observable in the cases of 4a and 4b . 26 All bond angles of I–C–B in both 4c and 6c are exceeding 125° and tilted away from each other, which indicates a remarkable van de Waals non-bonding interaction between two iodine groups, 19 in agreement with our previous assumption. The crystals of all dihalo-ABN nitro compounds exhibit interesting bricklayer arrangements with face-to-face π–π stacking mode (Fig.…”

“…In fact, its pinpoint synthesis constituted a multistep sequence of dinitration, reduction and Sandmeyer reaction to deliver the final product of 1,8-diiodonaphthalene. 19,20 This existing multistep approach is limited in scope and mired by the use of hazardous and strong oxidizing acids as well as poor selectivity issues, so is less likely to serve as a model for the synthesis of sensitive BN-heteroaromatics (Fig. 1).…”

“…21,22 It is worth noting that carbon-version diiodide 2 has been utilized as an important privileged motif existing in pharmaceutical and materials chemistry. 19,23–25 An efficient synthesis of its BN-isostere 4c becomes thus of high interest (Scheme 1). Furthermore, preparative methods with regioselective control for nitro-ABN compounds are still extremely underdeveloped.…”

Diaryl hypervalent bromines and chlorines: synthesis, structures and reactivities

“…More recently, Cuenca, Shafir and co-workers have announced the first examples of hetero di-λ 3 -diarylhalonium structures by reporting the iodine( iii )–bromine( iii ) and iodine( iii )–chlorine( iii ) bis-hypervalent compounds ( Scheme 15 ). 74 The synthetic strategy relies on a series of peculiar steps, an initial formation of the diaryl hypervalent iodane 59, followed by one-pot three consecutive steps of deprotection, oxidation and cyclization reactions to generate the second hypervalent species. Despite the moderate efficiency of this methodology, the originality of the new compounds 60 and 61 opens new perspectives in the field.…”

Predicting bond dissociation energies of cyclic hypervalent halogen reagents using DFT calculations and graph attention network model

“…Biphenyl hypervalent bromine(III) reagents [ 34 – 39 ] have been synthesized by Yoshida and Wencel-Delord ( Figure 1 ). Cyclic hypervalent chlorine(III) reagents with similar skeletal structures have not been reported yet, and only biphenyl hypervalent chlorine(III) reagents [ 40 – 42 ] and cyclic diaryliodonium salts [ 43 ] have been synthesized.…”