Microwave-induced Monohydroxymethylation and Monoalkoxylation of 1,4-Naphthoquinones$ Vandana Bansal, Jyotsana Sharma and Rajinder N. Khanna* Department of Chemistry, University of Delhi, Delhi-110007, India 1,4-Naphthoquinones and its derivatives have been hydroxymethylated and alkoxylated in the quinone ring using, respectively, formalin or an alcohol, in the presence of K2CO3 or HgO by heating or microwave irradiation. Several publications have described the use of commercially available microwave ovens for microwave induced organic reaction enhancement (MORE).1,2 The technique is energy- and cost-e�cient as well as convenient to use.The present communication reports the synthesis of hydroxymethylated and alkoxylated 1,4-naphthoquinones using microwave irradiation. It dramatically reduces the reaction time and increases the yield remarkably. Potassium carbonate or mercury(II) oxide in aqueous formalin were used for the introduction of hydroxymethyl group under thermal and microwave conditions at the active quinonoid position of 1,4-naphthoquinones 1 to give the 2-hydroxymethyl-1,4-naphthoquinones 2 (Scheme 1).Com- pounds 2a±d were identi®ed on the basis of their spectral data (Tables 1 and 2). Mercury(II) oxide in various alcohols (methanol, ethanol, isopropyl alcohol, propanol, isobutyl alcohol, butanol and allyl alcohol) was used for the introduction of alkoxy groups under thermal and microwave conditions at the active qui- nonoid position of 1,4-naphthoquinones (1a±c), to give the corresponding alkoxy compounds (3) (Scheme 1, Table 3).Compounds (3a±g) were identi®ed on the basis of spectral data (Table 4). Discussion In the hydroxymethylation of various quinones, it was observed that the presence of the reagent (K2CO3 or HgO) was essential and the monohydroxymethylated products were obtained without any polymerization or replacement of halo group in 1b and 1c in Scheme 1. The reaction failed to proceed with other aldehydes, e.g.acetaldehyde and benzal- dehyde. Yields were found to be higher with K2CO3 as com- pared to HgO. In the alkoxylation of various quinones, the presence of reagent (HgO) was also essential and the yield of alkoxy quinones decreased with the increase in the size of the alkyl group in the alcohol. The yield of alkoxy quinones is higher when halogenated quinones are alkoxylated because the halo group is a better leaving group. Microwave irradiation accelerates organic reactions by its high heating e�ciency giving rise to a remarkable rate enhancement and a dramatic reduction in reaction times (Tables 1 and 3).J. Chem. Research (S), 1998, 720±721$ Scheme 1 Table 1 Hydroxymethylation of 1,4-naphthoquinones (1a±d) Yield (%) t/min Found (required) (%) Quinone Reagent D m D m Molecular formula C H Lit. mp/8C 2a K2CO3 92 90 30 5 C11H8O3 70.2 (70.1) 4.25 (4.30) 1153 HgO 90 80 90 6 2b K2CO3 95 95 30 5 C11H7O3CI 59.3 (59.1) 3.1 (3.2) 1353 HgO 90 85 90 5 2c K2CO3 94 92 30 5 C11H7O3Br 49.5 (49.6) 2.6 (2.4) 1303 HgO 92 85 90 5 2d K2CO3 85 82 60 5 C12H10O3 71.2 (71.0) 4.9 (4.7) 106 HgO 80 78 90 6 Table 2 Spectral data of quinones 2a±d Quinone dH /cm¡1 2a 2.50 (s, broad, 1 H, OH), 4.60 (s, 2 H, CH2OH), 7.10 (s, 1 H, C3-H), 7.80± 8.10 (m, 4 H, Ar-H) 1620, 1650 2b 2.50 (s, broad, 1 H, OH), 4.60 (s, 2 H, CH2OH), 7.60±8.20 (m, 4 H, Ar-H) 1625, 1650 2c 2.50 (s, broad, 1 H, OH), 4.60 (s, 2 H, CH2OH), 7.60±8.10 (m, 4 H, Ar-H) 1625, 1650 2d 2.10 (s, 3 H, CH3), 2.60 (s, broad, 1 H, OH), 4.70 (s, 2 H, CH2OH), 7.20±8.00 (m, 4 H, Ar-H) 1625, 1655 Experimental Melting points are uncorrected.IR spectra were recorded on a Shimadzu IR-435 spectrometer (Nujol, cm¡1). NMR spectra were recorded on a Perkin-Elmer R-32 (90 MHz) in CDCl3, using TMS as internal standard. Chemical shifts were recorded on the d scale. $This is a Short Paper as de®ned in the Instructions for Authors, Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J. Chem. Research (M). *To receive any correspondence (e-mail: VandanaBansal@hotmail. com). 720 J. CHEM. RESEARCH (S), 1998General ProcedureMethod A.To a solution of the substrate(0.1 mol, 1a¡Ód) in 30% aqueous formaldehyde (20 ml), potassiumcarbonate (0.1 mol) or yellow mercury(II) oxide (0.1 mol) wasadded. The solution was reuxed for specied time (Table 1). Thereaction mixture was ltered and the ltrate concentrated underreduced pressure, diluted with water (100 ml) and the mixtureextracted with ethyl acetate (220 ml).The organic extract wasdried (MgSO4) and evaporated under reduced pressure to give asolid which was puried by preparative TLC (silica gel) usingbenzene¡Óethyl acetate (9:1) as a solvent to aord the hydroxy-methylated product (2a¡Ód).Method B.To a solution of the substrate (0.1 mol, 1a¡Ód) in30% aqueous formaldehyde (20 ml), potassium carbonate (0.1 mol)or yellow mercury(II) oxide (0.1 mol) was added.The mixture wassubjected to microwave irradiation at 2450 MHz for a specied time(Table 1). The reaction mixture was worked up as described aboveto aord the hydroxymethylated product (2a¡Ód).Method C.To a solution of the substrate (0.1 mol, 1a¡Óc) inthe alcohol (20 ml), yellow mercury(II) (0.1 mol) was added. Thesolution was reuxed for specied time (Table 3), cooled andltered. The ltrate was concentrated under reduced pressure,diluted with water (100 ml) and the mixture extracted with ethylacetate (220 ml).The organic extract was dried (MgSO4) andevaporated under reduced pressure to give a solid which was puri-ed by preparative TLC using benzene¡Óethyl acetate (8:2) as asolvent to aord the alkoxylated product (3a¡Óg).Method D.To a solution of the substrate (0.1 mol, 1a¡Óc) inalcohol (5 ml), mercury(II) oxide (0.1 mol) was added. The mixturewas subjected to microwave irradiation at 2450 MHz for a speciedtime (Table 3).The reaction was worked up as described earlier toaord the alkoxylated product (3a¡Óg).V.B. is grateful to UGC, New Delhi, for the award ofSRF.Received, 11th May 1998; Accepted, 28th July 1998Paper E/8/03513JReferences1 G. Nagy, S. V. Filip, E. Surducan and V. Surducan, Synth.Commun., 1997, 27, 3729.2 D. M. P. Mingos and D. R. Baghurst, Chem. Soc. Rev., 1991,20, 1.3 P. C. Thapliyal, J. Sharma, K. P. Singh and R. N. Khanna, Ind.J.Chem., 1995, 34B, 994.4 R. N. Khanna, K. P. Singh, S. K. Yadav and S. Srinivas, Synth.Commun., 1989, 19, 3151.5 L. F. Fieser, J. Am. Chem. Soc., 1926, 48, 2922.6 L. F. Fieser, J. Am. Chem. Soc., 1926, 48, 3201.Table 4 Spectral data of quinones 3d¡ÓeQuinone dH /cm£¾13d 1.00 (t, J 7.0, 3 H, CH3), 1.50¡Ó2.10(m, 2 H, CH2CH3), 3.80 (t, J 7.0,2 H, OCH2), 5.90 (s, 1 H, C3-H),7.30¡Ó7.90 (m, 4 H, Ar-H)1620, 16803e 1.10 (d, J 7.0, 6 H, 2 CH3), 1.90¡Ó2.40 (m, 1 H, OCH), 3.60 (d, J 7.0,2 H, OCH2), 5.90 (s, 1 H, C3-H),7.30¡Ó7.90 (m, 4 H, Ar-H)1640, 1680Table 3 Alkoxylation of 1,4-naphthoquinones (1a¡Óc)Yield (%) t/minQuinone Alcohol Product D m D m Mp/8C [lit. mp]1a CH3OH 3a 70 80 120 5 182 [182¡Ó183]41b 75 85 60 51c 70 85 60 51a CH3CH2OH 3b 65 75 120 5 116 [115¡Ó117]41b 80 85 60 51c 82 85 60 51a (CH3)2CHOH 3c 65 72 180 6 115 [115]41b 75 80 150 61c 80 86 150 61a CH3(CH2)2OH 3d 60 72 240 7 901b 65 75 180 61c 62 78 210 61a (CH3)2CHCH2OH 3e 55 65 240 7 781b 65 75 180 71c 60 78 180 71a CH3(CH2)3OH 3f 50 65 240 8 104 [104]51b 60 75 180 71c 62 75 180 71a CH2.CHCH2OH 3g 55 62 180 8 99 [98.5]61b 58 70 150 81c 60 72 150 8J. CHEM. RESEARCH (S), 1998