Synthesis of Naturally Occurring 5-Allyl-2-aryl-7-methoxybenzofuran and 2-Aryl-5-(3-hydroxypropyl)-7-methoxybenzofurans$ Raghao S. Mali* and Archna Patience Massey Garware Research Centre, Department of Chemistry, University of Pune, Pune-7, India A convenient and general procedure is described for the synthesis of 5-allyl-2-aryl-7-methoxybenzofurans (8a±e) from 2-allyloxy-3-methoxybenzaldehyde (3). The compounds 8a and 8b on hydroboration followed by oxidation provide the naturally occurring benzofurans (1a and 1b).A few compounds, containing the 2-arylbenzofuran nucleus (1a, 1b, 2 and 8a), have been isolated from plants.2±4 Egonol (1a) and homoegonol (1b) were isolated2,3 from the seeds of Styrax japonicum and Styrax o�cinalis L. respect- ively, while (2)-machicendiol 2 was isolated4 from the leaf extracts of Machilus glaucescens, which are used for the treatment of asthma, rheumatism and ulcers. These com- pounds are also reported for their cytostatic activity against human leukemic HL-60 cells.5 In view of the natural occurrence and valuable biological activities associated with 1a, 1b and 2, several methods have been developed for their synthesis.7±9,11 Four approaches are known7±9,11 for egonol 1a and one 8,9 each for homo- egonol 1b and neolignan 8a.We report herein a convenient, general approach (Scheme 1) for the synthesis of egonol 1a, homoegonol 1b and neolignan 8a, starting from 2-allyloxy-3-methoxy- benzaldehyde13 3.When a solution of aldehyde 3 in N,N-dimethylaniline was irradiated in a microwave oven for 10 min, 5-allyl-2-hydroxy-3-methoxybenzaldehyde 4 was obtained in 65% yield along with minor amount (15%) of 2-allyl-6-methoxyphenol. The aldehyde 4 on reduction with sodium tetrahydroborate in ethyl acetate solution, gave the benzyl alcohol 5 as a thick liquid in 76% yield. Reaction of 5 with thionyl chloride in methylene chloride, followed by treatment with triphenylphosphine in benzene solution yielded the phosphonium salt 6, which on reaction with benzoyl chlorides in toluene solution, in the presence of J.Chem. Research (S), 1998, 230±231 J. Chem. Research (M), 1998, 1109±1120 Scheme 1 triethylamine, furnished the 2-arylbenzofurans (8a±e) in 60±89% yields via the intermediacy of phosphonium salts 7a±e. $Dedicated to Professor Dr Dieter Seebach on the occasion of his 60th birthday. *To receive any correspondence (e-mail: rsmali@chem.unipune. ernet.in). 230 J.CHEM. RESEARCH (S), 1998The present work thus describes the total synthesis of neolignan 8a and the related compounds 8b�}e. Conversion of 2-arylbenzofuran 8a into egonol 1a has already been reported8 in the literature using the hydroboration approach. The compound 8b on similar reaction provided homoegonol 1b, mp 121 8C (lit.,3 mp 120�}122 8C) in 70% yield, which is another natural product. We thank Professor N. S. Narasimhan for critical reading of the manuscript and valuable discussions.A.P.M. thanks CSIR, New Delhi for the award of Senior Research Fellowship. Techniques used: IR, 1H NMR, elemental analyses, TLC and column chromatography References: 15 Received, 17th October 1997; Accepted, 14th January 1998 Paper E/7/07498K References cited in this synopsis 2 H. Okada, J. Pharm. Soc. Jpn., 1915, 657. 3 R. Segal, I. M. Goldzweig, S. Sokolo€ and D. V. Zaitschek, J. Chem. Soc. C, 1967, 2402. 4 B. Talaparta, T. Ray and S. Talaparta, Indian J. Chem., Sect. B, 1976, 14, 613. 5 T. Hirano, M. Goto and K. Oka, Life Sci., 1994, 55, 1061. 7 S. Kawai, T. Nakamura and N. Sugiyama, Ber. Dtsch. Chem. Ges., 1939, 72, 1146. 8 E. Ritchie and W. C. Taylor, Aust. J. Chem., 1969, 22, 1329. 9 F. G. Schreiber and R. Stevenson, J. Chem. Soc., Perkin Trans. 1, 1976, 1514. 11 Y. Aoyagi, T. Mizusaki, A. Hatori, T. Asakura, T. Aihara, S. Inaba, K. Hayatsu and A. Ohta, Heterocycles, 1995, 41, 1077. 13 R. S. Mali and A. P. Massey, Indian J. Chem., Sect. B, 1995, 34, 686. J. CHEM. RESEARCH (S), 19