[121309-88-4] · C10H16Cl4IN · Benzyltrimethylammonium Tetrachloroiodate · (MW 418.96)
Physical Data: mp 106-125 °C (sinters at 106-107 °C, and melts completely at 125 °C).
Solubility: sol MeCN, MeNO3, DMSO, DMF; slightly sol MeOH, EtOH, AcOH, AcOEt, CHCl3, CH2Cl2; insol C6H14, CCl4, C6H6, H2O.
Form Supplied in: yellow needles.
Analysis of Reagent Purity: 1H NMR (CD3CN) d 3.07 (s, 9H, 3 CH3), 4.40 (s, 2H, CH2), 7.50 (s, 5H, C6H5).
Preparative Methods: chlorine gas is bubbled into a solution of benzyltrimethylammonium chloride (18.6 g, 0.1 mol) and iodine (12.7 g, 0.05 mol) in CH2Cl2 (300 mL) for 15 min; yield 40 g (95%).2 For alternative methods, see Kajigaeshi et al.3
Handling, Storage, and Precautions: stable solid, but gradually decomposes with evolution of Cl2 when in contact with air for a long time. This reagent should be handled in a fume hood.
This solid reagent (1) is used to chlorinate aromatic compounds (eq 1) and is considerably safer and more convenient to use than toxic gaseous Chlorine.
The reaction of phenols with (1) in CH2Cl2 at room temperature gives chloro-substituted phenols (66-91% yield). In these cases the chlorination of phenols having an electron-donating groups in the aromatic ring gives polychloro-substituted phenols; however, chlorination of phenols having electron-withdrawing groups can be controlled step by step.4
The reaction of aromatic amines with a calculated amount of (1) in AcOH at room temperature or at 70 °C gives chloro-substituted aromatic amines (66-99% yield). The active species in these chlorinations may be acetyl hypochlorite (AcOCl). In these cases, chlorination of amines having electron-withdrawing groups in the aromatic ring gives the desired chloro-substituted products, but chlorination of amines having electron-donating groups leads to oxidation products.5
The reaction of aromatic ethers with a calculated amount of (1) in AcOH or CH2Cl2 under mild conditions gives, selectively, chloro-substituted aromatic ethers (71-96% yield). Chlorination of nitroanisoles is unsuccessful.6
The reaction of acetanilides with a calculated amount of (1) in AcOH at room temperature or at 70 °C gives, selectively, the desired chloro-substituted acetanilides (81-93% yield). Chlorination of nitroacetanilides does not proceed.7
The reaction of arenes with a calculated amount of (1) in AcOH at room temperature or at 70 °C gives aromatic chlorides (40-99% yield). Thus treating 1,3,5-trimethylbenzene with 1, 2, and 3 equiv of (1) gives 1-chloro-, 1,3-dichloro-, and 1,3,5-trichloro-2,4,6-trimethylbenzene, respectively, in good yields.8 The reaction of thiophenes with (1) in AcOH at room temperature or at 70 °C gives chloro-substituted thiophenes. For example, the reaction of 3-methylthiophene with 2 equiv of (1) gives 2,5-dichloro-3-methylthiophene in 81% yield.9
The reaction of arenes with (1) in CCl4 in the presence of AIBN under reflux gives a-chloro-substituted compounds. Thus the reaction of toluene with 1 equiv of (1) for 4 h gives benzyl chloride and benzylidene dichloride in 77% and 11% yield, respectively.3 The reaction of acetophenones (eq 2) with 1 equiv of (1) in ClCH2CH2Cl-MeOH under reflux gives a-chloroacetyl derivatives (95-99% yield). Thus treating acetophenone with (1) for 3 h gives a 99% yield of a-chloroacetophenone.2 The reaction of acetophenones with 2 equiv of (1) in AcOH at 70 °C gives a,a-dichloroacetyl derivatives (66-99% yield). In this fashion, the chlorination of acetophenone with 2 equiv of (1) for 5 h gives 2,2-dichloro-1-phenylethanone in 90% yield.10
The reaction of alkenes with 1 equiv of (1) in CH2Cl2 at room temperature gives the expected chlorine adducts in a nonstereospecific manner (eq 3). In MeOH or AcOH this reaction produces chlorine adducts along with solvent-incorporated products in a regioselective manner.11
Yamaguchi University, Ube, Japan
Ube Technical College, Ube, Japan