Introduction of Synthesis of Hypervalent Iodine Compounds and Their Reactivity in Ligand Exchange Reactions

In recent years, the impressive development in the field of hyper-valent chemistry is evident by a large number of publications. The first synthesis of hyper valent iodine was investigated in 100 years back. The efficient production was from metal free reagents and the contribution of the process have an influence on the applications of hyper-valent iodine reagents synthesis 1. The selective property of the compound is an oxidizing capability that transforms it into the complex organic molecule and environmental characteristics. In previous 5-6 years, particularly noteworthy work have been published 2. The commemorative issue was discussed by Prof. Anastasios Varvolgis through his 22 research articles about the hypervalent iodine (III) 3. A research was conducted by Wang and Studer in 2017 to determine the reduction of the transition metal free single electron for the generation of radicals and transformation of the material into ligand of I (III) reagents for the substrate 2.  

In the present work, preparation, synthesis, and reactions of the hyper-valent (III) reagents are overviewed. The application of hypervalent reagent is to allow some transformation of oxidation into the facile and environmental friendly compounds. The transformation process makes it useful for the recyclable reagent process as a catalyst, radical reactivity, heteroatom radical generation, and valuable ionic reactivity 1. The goal of the present work is to synthesize hypervalent iodine reagents by three processes including synthesis of dichloroiodate benzene (PhICl2), kinetics of the formation of (PhICl2), and Ligand exchange reaction between the  (PhICl2) and (PhI(O2CCH3)2).  

Experimental of Synthesis of Hypervalent Iodine Compounds and Their Reactivity in Ligand Exchange Reactions

In the present work, synthesizes of (dichloroiodo) benzene PhICl2 was done by reaction of iodobenzene and chlorine and the final production was yellow needle-like structures of PhICl2. The synthesis process required a precise amount of iodobenzene (1.0 ml, 1.823 g, and 8.9 mol), glacial acetic acid (10 ml), sulfuryl chloride (1.08 ml, 1.08ml, and 13.3 mol). The whole composition was added to the 0.5- 0.6 ml of CDCl3. The other solutions used in the synthesis are 1.12 ul of iodobenzene (0.01 m mol), CDCO2D (1.0 ml), and PhI(O2CCH3)2 (12.9 mg, 0.04 m mol and 1 ml of CDCl3. The other products like hexane and pentane were required to wash and clean the crystals.

The NMR spectra were recorded by using spectrometer (SGI/Bruker DRX-400) and the solvents used for the measurement of spectra. The positive chemical shifts of H1 and C13 NMR and in case of Si29, C13 was determined as downfield shift and the external reference spectra were used for the Me4Si and H3PO4. For the elemental analysis of the solution and produced reagent IR spectra was used by Carlo Erba Strumentazione (CHN Elemental Analyzer 1106) and the other spectrometer used in the analysis was Nicolet 560 IR spectrometer.    

The first step is the formation of dichloroiodo benzene (PhICl2), for this purpose, a 50 –ml beaker was filled with 10 ml of glacial acetic acid, 1.08 ml of sulfuryl chloride (1.802 g and13.3 mol), and iodobenzene (8.9 mmol and 1.823 g). The mixture was mixed with the glass rod and beaker was placed in the dark for the crystallization. After one hour the crystals were washed and a small amount of CDCl3 was added to the product due to purity. In the second step, kinematics formation of (PhICl2), 1.0 ml of CD3CO2D was mixed with 1.12 l of iodobenzene (0.01 m mol) for the formation of 20 mM solution. After that 0.8 mL solution was dropped in NMR tube. The micropipette was used to add 13 l of SO2Cl2 in the NMR tube. The spectrum was then measured after “x-seconds” and the reagents were collected after time “x-17” time and “x+17” corresponding time. In the third step, the ligand exchange reaction was carried out between PhICl2 and PhI(O2CCH3)2. The solution of 40 mM was prepared by adding PhICl2 with1 ml of CDCl3. The solution was a mixture of 1:1 ratio of volume in the NMR.  

Results and discussion of Synthesis of Hypervalent Iodine Compounds and Their Reactivity in Ligand Exchange Reactions

In the present work, yellow crystal like structures of (dichloroiodo) benzene PhICl2 is produced by the reaction of iodobenzene and chlorine. After mixing the reactants the solution was placed in the dark. Sulfurlyl chloride was used in the reaction to produce sulfur dioxide and reaction products remained pure and it was not contaminated. The main reaction was due to the addition of glacial acetic acid. The formed salutation was filtered and washed with hexane and pentane. The metal content was avoided with the mixture. The NMR tube was first filled with the products and then shake it well to mix the products properly. The NMR spectra were collected after the 30-35 minutes of changes. The spectra were given as a function of time and concentration of PhICl3. The equilibrium constant was then calculated from observed plots 4.

Synthesis of benzene (PHICl3) of Hypervalent Iodine Compounds and Their Reactivity in Ligand Exchange Reactions

The difference between the chemical shift of spectra for the iodobenzene and PhICl3 is due to time variation after the solution formation. The size of crystal changes due to change in the composition and level of reaction at any time. The time difference for the reaction is from 2-14 min. The shift in the spectra was estimated by the change in the peak as shown in figure 2 in the appendix. The experiment requires to re-do the NRM readings because contamination of water is observed.

After the reaction the of hyper-valent iodine with the metals the chemical properties of the heavy metals changes. The reactivity possesses due to transition metals and the deoxidizing process of metal takes place as a catalytic cycle. The process is known as metal dependent halogenation or sometimes the reaction is known as coupling reactions 5. The reaction of hypervalent iodine with the copper and nickel gives meso-chlorinated products and the products are without any kind of coupling bisporphrins 6. After the crystallization process of 1:15 hours the yielded crystal was 1.66 grams.      

Dichlooriodo was placed in the dark and isolated state to avoid heat and light. The mixture is mainly sensitive to the yellow light and insufficiently less stable to the high temperature, therefore, it is necessary to place the solution in low temperature. 

Kinetics of Formation of PhICl3 in the solution

The reaction in the first section presents a zero order and first order reaction and the kinetic plot is used to estimate the formation of products in the reaction. The spectra is a plot function that is between ln (I conversion) against time and the conversion of production fraction is determined for the iodobenzene conversion for the PhICl2. Approximately 1.12ul (0.01 m mol) iodobenzene was added to the reaction    

The plot shows the concentration of the reactants when the initial stock was about 120 mM. The NMR graph shows kinetics measured for the exchange reaction between CDCl3, PhICl2, and PhI(O2 CCH3)2. The graphical representation demonstrates the higher concentration and formation of the hyper valent iodine (III) species in the reaction.  The proper scaling of the graphs was important to measure the concentration of the PhICl2 in the reaction.

 The reaction parameters that were expected to the have impact on the concentration constant can be listed as concentration difference between the products and reactants, temperature variation or time duration for the reaction 7.

References  of Synthesis of Hypervalent Iodine Compounds and Their Reactivity in Ligand Exchange Reactions
1.Wirth, T., Hypervalent iodine chemistry in synthesis: Scope and new directions. Angewandte Chemie International Edition 2005, 44 (24), 3656-3665.
2:Wang, X.; Studer, A., Iodine(III) Reagents in Radical Chemistry. Accounts of Chemical Research 2017, 50 (7), 1712-1724.
3. Zhdankin, V. V., Hypervalent iodine (III) reagents in organic synthesis. ARKIVOC: Online Journal of Organic Chemistry 2009.
4.  Zhdankin, V. V., Hypervalent iodine chemistry: preparation, structure, and synthetic applications of polyvalent iodine compounds. John Wiley & Sons: 2013.
5. Varvoglis, A., Hypervalent iodine in organic synthesis. Academic Press: 1996.
6: Jin, L.-M.; Yin, J.-J.; Chen, L.; Guo, C.-C.; Chen, Q.-Y., Metal-dependent halogenation and/or coupling reactions of porphyrins with PhIX2 (X= Cl, F). Synlett 2005, 2005 (19), 2893-2898.
7:  Kieltsch, I.; Eisenberger, P.; Togni, A., Mild Electrophilic Trifluoromethylation of Carbon‐and Sulfur‐Centered Nucleophiles by a Hypervalent Iodine (III)–CF3 Reagent. Angewandte Chemie 2007, 119 (5), 768-771.