O O Hg HgCl R R O O + a R = H b R = 4-Me c R = 4-Cl d R = 4-Br e R = 4-OMe 2a–e heat or microwave 1 52 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 52–53† Microwave-induced Selective Mercuration of 1,4-Naphthoquinone† Mazaahir Kidwai,* Seema Kohli and Parven Kumar Department of Chemistry, University of Delhi, Delhi-110007, India An efficient mercuration of 1,4-naphthoquinone at the C-2 position is reported using arylmercury(II) chloride under microwave irradiation. Recently there has been much interest in the use of microwave irradiation in synthesis1 owing to substantial reductions in reaction times.In continuation of our earlier work2–6 on microwave-assisted synthesis it was thought worthwhile to synthesize the mercury-containing 1,4-naphthoquinone under microwave activation. The microwave procedure for the mercuration owes its importance to the fact that the reaction is completed in 2–4 min with improved yields when compared to conventional heating which requires 12–13 h.A comparative study in terms of yield and reaction time is also reported (Table 2) using conventional heating. Experimental Mps (uncorrected) were recorded on an Electrothermal apparatus. The purities of the compounds were checked on silica-coated Al plates (Merck). General Procedure for the Synthesis of Arylmercury (II) Chloride 1a–e.•Mercury(II) acetate (0.01 mol) was added to a mixture of DMF (10 ml) and benzene/toluene/chlorobenzene/bromobenzene/ anisole (0.1 mol) in a 100 ml beaker and the mixture was irradiated in a microwave oven for 1.0–1.5 min at 2450 MHz.The contents were concentrated in vacuo to remove most of the unreacted benzene/toluene/chlorobenzene/bromobenzene/anisole and DMF. To this, EtOH (15 ml) was added. A boiling aqueous solution of NaCl (0.01 mol) was added slowly with stirring when a white precipitate separated out. The solid obtained was filtered off, washed with water, dried and recrystallized from acetone. The melting points were comparable to the reported mps7–11 and are given in (Table 1).General Procedure for the Synthesis of 2-[arylmercury (II)]- 1,4-naphthoquinone 2a–e.•Method A (thermal ). To a solution of 2 (0.01 mol in 15 ml acetone) anhydrous K2CO3 (2 g) and arylmercury( II) chloride (0.01 mol) were added (Scheme 1). The reaction mixture was stirred under reflux for a specified time (Table 2). It was then cooled and filtered to remove the inorganic salt; excess of solvent from the clear filtrate was evaporated under reduced pressure. The solid obtained was filtered off, dried and recrystallized from acetone–light petroleum (bp 40–60°C).Method B (microwave irradiation). To a solution of 2 (0.01 mol) in N,N-dimethylacetamide anhydrous K2CO3 (2 g) and arylmercury (II) chloride (0.01 mol) were added in a 100 ml beaker. The beaker was irradiated in a microwave oven for 2.0–3.0 min at 2450 MHz. The reaction mixture was cooled and filtered to remove the inorganic salt.Excess of solvent was evaporated under pressure. *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Arylmercury(II) chlorides produced Reaction time Mp (T/°C) % Yield Compound R Lit./h M.W.I.a/min Found Lit. Lit. M.W.I.a 1a 1b 1c 1d 1e H 4-Me 4-Cl 4-Br 4-OMe 3.0b 4.0c 4.5d 5.0e 5.0f 1.0 1.0 1.5 1.5 1.5 256–258 237 208–210 248–249 247–248 258b 238–239c 210d 250e 250f 80b 75c 70d 60e 55f 90 80 80 75 65 aM.W.I.=microwave induced.bRef. 7. cRef. 8. dRef. 9. eRef. 10. fRef. 11. Table 2 Comparison of reaction times and yields obtained using microwave-induced (M.W.I.) and classical method % Yield (time/min) % Yield (time/h) Compound R Mol. formula M.W.I. Classical method Mp(T/°C) 2a 2b 2c 2d 2e H 4-Me 4-Cl 4-Br 4-OMe C16H10HgO2 C17H12HgO2 C16H9ClHgO2 C16H9BrHgO2 C17H12HgO3 85 (2) 78 (2.3) 70 (2.3) 65 (2.5) 64 (3) 80 (12) 69 (13) 68 (12) 60 (12) 60 (13) 210 200–202 212–213 195 188–190J.CHEM. RESEARCH (S), 1998 53 The solid obtained was filtered off, dried and recrystallized from acetone–light petroleum (bp 40–60°C). Received, 28th July 1997; Accepted, 22nd September 1997 Paper E/7/05428I References 1 S. Caddick, Tetrahedron, 1995, 51, 10403. 2 M. Kidwai, R. Kumar and Y. Goel, Main Group Metal Chem., 1997, 6, 367. 3 M. Kidwai, P. Kumar and S. Kohli, J. Chem. Res. (S), 1997, 24. 4 M. Kidwai and P. Kumar, J. Chem. Res. (S), 1996, 254. 5 M. Kidwai and P. Kumar, J. Chem. Res. (S), 1997, 178. 6 M. Kidwai, P. Kumar, Y. Goel and K. Kumar, Indian J. Chem., 1997, 36B, 175. 7 E. Michael, J. Perie and A. Lattes, J. Organomet. Chem., 1981, 1, 204. 8 A. N. Nesemeyanov, Ber. Dtsch. Chem. Ges., 1929, 62, 1010. 9 M. E. Hanke, J. Am. Chem. Soc., 1923, 45, 1321. 10 A. N. Nesmeyanov, L. G. Makarova and I. V. Polovyanyuk, J. Gen. Chem. USSR, 1965, 35, 682. 11 P. J. Banney and P. R. Wells, Aust. J. Chem., 1971, 24, 317.