Microwave assisted solvent free synthesis of 1,3-diphenylpropenones
© Kakati et al 2011
Received: 19 September 2010
Accepted: 18 February 2011
Published: 18 February 2011
1,3-Diphenylpropenones (chalcones) are well known for their diverse array of bioactivities. Hydroxyl group substituted chalcones are the main precursor in the synthesis of flavonoids. Till date various methods have been developed for the synthesis of these very interesting molecules. Continuing our efforts for the development of simple, eco-friendly and cost-effective methodologies, we report here a solvent free condensation of aryl ketones and aldehydes using iodine impregnated alumina under microwave activation. This new protocol has been applied to a variety of substituted aryl carbonyls with excellent yield of substituted 1,3-diphenylpropenones.
Differently substituted chalcones were synthesized using iodine impregnated neutral alumina as catalyst in 79-95% yield in less than 2 minutes time under microwave activation without using any solvent. The reaction was studied under different catalytic conditions and it was found that molecular iodine supported over neutral alumina gives the best yield. The otherwise difficult single step condensation of hydroxy substituted aryl carbonyls is an attractive feature of this protocol to obtain polyhydroxychalcones in excellent yields. In order to find out the general applicability of this new endeavor it was successfully applied for the synthesis of 15 different chalcones including highly bioactive prenylated hydroxychalcone xanthohumol.
A new, simple and solvent free method was developed for the synthesis of substituted chalcones in environmentally benign way. The mild reaction conditions, easy work-up, clean reaction profiles render this approach as an interesting alternative to the existing methods.
1,3-Diphenylpropenones (chalcones) exhibit a broad spectrum of biological activities . These are the main precursor in the biosynthesis of flavonoids  abundant in edible plants. They have been reported to show various pharmacological activities like anticancer [3, 4], antimalarial , anti-inflammatory , anti-tubercular , cytotoxic , gastroprotective , modulation of nitric oxide production  and so on. These compounds are important synthons for the preparation of five and six membered ring systems  as well as intermediate in the synthesis of many pharmaceuticals . Having such a varied pharmacological activity and synthetic utility, chalcones have attracted chemists to develop newer strategies for their synthesis.
By far the most popular way of synthesis of chalcone is the Claisen-Schmidt condensation of an appropriate acetophenone with benzaldehyde in presence of aqueous bases like NaOH [13–15], KOH , Ba(OH)2 [17, 18] etc. Other base catalysts such as magnesium t-butoxide , potassium carbonate , alumina , MgO , calcinated hydrotalcites [23, 24], natural phosphate/NaNO3 [25, 26], KF/natural phosphate  and piperidine  have also been used for their synthesis.
The various activities of chalcones are largely dependent on the number and positions of hydroxy, methoxy and other substituent groups in both A and B rings . Hydroxy chalcones are the main synthon for the synthesis of a number of naturally occurring bioactive flavonoids . Literature data reveals that presence of hydroxyl substituent on the benzaldehyde aromatic ring hinders the base catalyzed aldol reaction. This happens because of the decreased reactivity of the carbonyl component due to the delocalization of the phenoxide anion formed . Thus it becomes necessary to use protecting groups to stop the formation of the phenoxide ion in the preparation of hydroxychalcones under basic conditions [31, 32]. This problem can be overcome by using acid catalysts like HCl, BF3, B2O3, PTSA, SOCl2/EtOH , AlCl3 , BF3-Et2O , TiCl4 , zeolites , RuCl3 , Bronsted acidic ionic liquids  and H2SO4 in AcOH , but many of them suffer from the drawbacks of lower yields and harsh, environmentally detrimental reaction conditions.
In an ongoing project on the synthesis of bio-active molecules, we required a number of hydroxychalcones. The results obtained using existing methods were not satisfactory. We therefore tried some new catalysts for this conversion including iodine-alumina because of our previous experience of using iodine as an inexpensive, nontoxic, readily available catalyst in many other reactions [40–44]. Due to stringent and growing environmental regulations, the chemical industry needs the development of more eco-compatible synthetic methodologies . The use of heterogeneous catalysts under solvent free conditions represents a potentially valuable and clean route to a range of organic products . Microwave assisted synthetic reactions are gaining importance in recent years because of its endorsement under Green chemistry protocol [47, 48]. We found iodine-alumina to be an excellent catalyst for the synthesis of chalcones under microwave irradiation giving 79-95% yield in a very short reaction time. During the preparation of this manuscript, Sashidhara et al  reported the synthesis of chalcones using iodine as catalyst but their method suffers from the requirement of dry dioxane as solvent and longer reaction time.
Results and discussions
Condensation of A and B under different reaction conditions:
Catalyst loading a
Synthetic chalcones prepared using Iodine-alumina under microwave irradiation:
4'-OCH2CH = CH2
The electron donating and electron withdrawing substituents in the aryl ring of the ketones or of the aldehydes were well tolerated to give moderate to high yields of the desired chalcones. In general the reaction was clean and no side products were detected.
This new method of preparation of chalcones is particularly attractive since it specifically generates the E isomer from substituted benzaldehyde and acetophenones, a large number of which or their derivatives show one or the other biological activity. Inspection of the 1H NMR spectra clearly indicates that the chalcones were both geometrically pure and were configured trans.
All commercially available chemicals and reagents were purchased from Aldrich and used without further purification. Melting points were determined with a Buchi B 540 apparatus in open capillaries and are uncorrected. IR spectra were recorded on a Perkin-Elmer 1640 FT-IR instrument. The 1H- and 13C-NMR spectra were recorded on Bruker DPX-300 NMR machine. Unless otherwise specified, CD3OD and CDCl3 were used as solvent. Mass spectra were recorded with a Trace DSQ GCMS system. Elemental analyses were carried out using a Perkin- Elmer series II CSNS/O Model 2400 analyzer. The I2-Al2O3 catalyst was prepared by the procedure reported earlier .
In conclusion, we have developed a new, simple and solvent free method for the synthesis of substituted chalcones using iodine-alumina. The mild reaction conditions, clean reaction profiles, zero side product and cost efficiency render this approach as a useful alternative to the existing methods. Further studies on the application of this method for the synthesis of highly functionalized biologically active chalcones are underway.
4'-Hydroxy acetophenone (100 mg, 0.735 mmol), 4-hydroxy benzaldehyde (90 mg, 0.735 mmol) and 200 mg 5% I2-Alumina was taken and homogenized in a mortar. Then the mixture was irradiated in a reaction vessel of a Synthwave 402 Prolabo focused microwave reactor for 80 seconds after setting reaction temperature at 60°C and power at 40% (maximum output 300 W). After cooling to room temperature ethyl acetate (15 mL) was added to the reaction mixture and filtered the mixture through a general laboratory filter paper to separate the solid catalyst. After washing the filtrate with Na2S2O3 solution (1 × 15 mL) and water (1 × 15 mL) the separated organic layer was concentrated under reduced pressure and the product was recrystallized from hot ethanol.
Analytical data of some new compounds as well as melting points of known compounds with their literature values are given below.
1,3-Diphenylpropenone (Entry 1)
Yellow needles. M.P. 56-57°C, Lit. [56-57°C] 
3-(4-Hydroxyphenyl)-1-phenylpropenone (Entry 2):
Pale yellow solids. M.P. 181-182°C, Lit. [180-181°C] 
1-(2-Hydroxyphenyl)-3-phenylpropenone (Entry 3):
Pale yellow solids. M. P. 88°C, Lit. [88°C] 
Fine yellow crystals. M. P. 55°C. IR (KBr) 1660, 1590, 1451, 1310, 1253, 1036, 778. 1H NMR (300 MHz, CD3OD): 6.0 (s, 2H, CH2O2); 6.9 (d, J = 8.0, 1H, 3-H); 7.25 (dd, J = 1.6, 8.4, 1H, 6-H); 7.4 (d, J = 1.6 Hz, 1H, 1-H); 7.53-7.66 (m, 4H, 3'-H, 5'-H, α-H, 4'-H); 7.7 ( d, J = 15.6, 1H, β-H); 8.11-8.10 ( m, 2H, 2'-H, 6'-H). 13C NMR (75 MHz, CDCl3):122.07 (O-CH2-O), 128.49 (C-3, C-6), 128.54 (C-α, C-1), 128.66 (C-3', C-5'), 128.99 (C-2', C-6'), 130.6 (C-1), 132.84 (C-4'), 134.88 (1'), 138.2 (C-β), 144.9 (C-4, C-5), 190.61 (C = O). MS (ESI+): m/z 253 [M+H] +. Anal. Calcd. for C16H12O3: C 76.18, H 4.79. Found: C 76.21; H 4.81.
1,3-Bis(4-hydroxyphenyl)propenone (Entry 5):
Yellow solid. M. P. 197-198°C, Lit. [196-198°C] 
3-(4-Chlorophenyl)-1-(4-methoxyphenyl)-propenone (Entry 6):
Pale yellow crystals. M. P. 130-131°C, Lit. [130-131°C] 
1-(4-Hydroxyphenyl)-3-(4-methoxyphenyl)-propenone (Entry 7):
Pale yellow solid. M. P. 183-184°C, Lit. [184-185°C] 
3-(4-Nitrophenyl)-1-phenylpropenone (Entry 8):
Pale yellow solid. M. P. 162°C, Lit. [155-157°C] 
3-(3,4-Dihydroxyphenyl)-1-phenylpropenone (Entry 9):
Pale yellow solid. M. P. 200-201°C, Lit. [202-204°C] 
3-(4-Hydroxy-3-methoxyphenyl)-1-(2-hydroxyphenyl)-propenone (Entry 10):
Yellow solid. M. P. 155-157°C, Lit. [153-156°C] 
1-(3-Hydroxyphenyl)-3-(2-nitrophenyl)-propenone (Entry 11):
Pale yellow solid. M. P. 185-186°C, Lit. [187-189°C] 
1,3-Bis-(4-methoxyphenyl)-propenone (Entry 12):
Yellow crystals. M. P. 100°C, Lit. [98-100°C] 
3-(3,4-Dihydroxyphenyl)-1-(4-hydroxyphenyl)-propenone (Entry 13):
Pale yellow solid. M. P. 219-220°C, Lit. [218-219°C] 
1-(4-Allyloxyphenyl)-3-(4-methoxyphenyl)propenone (Entry 14):
Light yellow crystals. M. P. 76°C. IR (KBr): 2925, 2839, 1658, 1602, 1511, 1254, 1016, 818. 1H NMR (300 MHz, CDCl3): 3.85 (s, 3H, OCH3), 4.63 (s, 2H, 2''-H), 5.31 (d, Jcis = 10.3, 1H, 4''-H); 5.42 (d, Jtran s = 17.3, 1H, 4''-H); 6.08 (m, 1H, 3''-H); 6.92-7.0 (m, 4H, 3-H, 5-H, 3'-H, 5'-H); 7.46 (d, J = 15.6, 1H, α-H); 7.6 (d, J = 7.6, 2H, 2-H, 4-H); 7.8 (d, J = 15.5, 1H, β-H); 7.94-8.04 (m, 2H, 2'-H, 6'-H). 13C NMR (75 MHz, CDCl3): 55.42 (OCH3), 68.91 (2''-C), 114.38 (3-C, 5-C), 114.49 (3'-C, 5'-C), 118.23 (4''-C), 119.49 (C-α), 127.79 (C-1), 130.14 (C-2, C-6), 130.7 (C-2', C-6'), 131.43 (C-1'), 132.55 (3''-C), 143.86 (β-C), 161.51 (4-C), 162.26 (4'-C), 186.76 (C = O). MS (ESI+): m/z 295 [M+H] +. Anal. Calcd. for C19H18O3: C 77.53, H 6.16. Found: C 77.51; H 6.19.
1-(2,4-Dimethoxy-phenyl)-3-(4-methoxy-phenyl)-propenone: (Entry 15)
Yellow crystals. M. P. 84°C. IR (CHCl3): 2938, 1651, 1573, 1251, 1126, 1026, 828. 1H NMR (300 MHz, CDCl3): 3.85 (s, 3H, OCH3); 3.87 (s, 3H, OCH3); 3.9 (s, 3H, OCH3); 6.49 (d, J = 2.2, 1H, 3'-H); 6.54 (dd, J = 2.2, 8.6, 1H, 5'-H); 6.9-6.94 (m, 2H, 3-H, 5-H); 7.36 (d, J = 15.8, 1H, α-H); 7.53 (d, J = 9.7, 2H, 2-H, 6-H); 7.62 (d, J = 15.7, 1H, β-H); 7.73 (d, J = 8.6, 1H, 6'-H). 13C NMR (CDCl3, 75 MHz): 55.39 (OCH3), 55.56 (OCH3), 55.76 (OCH3), 98.66 (C-3'), 105.07 (C-5'), 114.29 (C-3, C-5), 122.44 (C-1'), 124.98 (C-α), 128.14 (C-1), 130.01(C-2, C-6), 132.75 (C-6'), 142.11 (C-β), 160.25 (C-4), 161.23 (C-2'), 163.97 (C-4'), 190.71 (C = O). MS (ESI+): m/z 298.6 [M+H] +. Anal. Calcd. for C18H18O4: C 72.47, H 6.08. Found: C 72.50; H 6.10.
The authors thank the Director, NEIST for providing necessary facilities, the Analytical Chemistry Division, NEIST for their help and Dr. N C Barua for constant encouragement.
- Li Y, Fang H, Xu W: Recent advance in the research of flavonoids as anticancer agents. Mini-Rev. Med. Chem. 2007, 7: 663-670. 10.2174/138955707781024463.View ArticleGoogle Scholar
- Dhar DN: The Chemistry of Chalcones and Related Compounds. 1981, John Wiley and Sons: New YorkGoogle Scholar
- Anto RJ, Sukumaran K, Kuttan G, Rao MNA, Subbaraju V, Kuttan R: Anticancer and antioxidant activity of synthetic chalcones and related compounds. Cancer Lett. 1995, 97: 33-37. 10.1016/0304-3835(95)03945-S.View ArticleGoogle Scholar
- Xia Y, Yang ZY, Xia P, Bastow KF, Nakanishi Y, Lee KH: Antitumor Agents. Part 202: Novel 2'-Amino Chalcones: Design, Synthesis and Biological Evaluation. Bioorg. Med. Chem. Lett. 2000, 10: 699-701. 10.1016/S0960-894X(00)00072-X.View ArticleGoogle Scholar
- Li R, Chen X, Gong B, Dominguez JN, Davidson E, Kurzban G, Miller RE, Nuzum EO, Rosenthal PJ: In Vitro Antimalarial Activity of Chalcones and Their Derivatives. J. Med. Chem. 1995, 38: 5031-5037. 10.1021/jm00026a010.View ArticleGoogle Scholar
- Ballesteros JF, Sanz MJ, Ubeda A, Miranda MA, Iborra S, Paya M, Alcaraz MJ: Synthesis and Pharmacological Evaluation of 2'-Hydroxychalcones and Flavones as Inhibitors of Inflammatory Mediators Generation. J. Med. Chem. 1995, 38: 2794-2797. 10.1021/jm00014a032.View ArticleGoogle Scholar
- Lin YM, Zhou Y, Flavin MT, Zhou LM, Nie W, Che FC: Chalcones and Flavonoids as Anti-Tuberculosis Agents. Bioorg. Med. Chem. 2002, 10: 2795-2802. 10.1016/S0968-0896(02)00094-9.View ArticleGoogle Scholar
- Bhat BA, Dhar KL, Puri SC, Saxena AK, Shanmugavel M, Qazi GN: Synthesis and biological evaluation of chalcones and their derived pyrazoles as potential cytotoxic agents. Bioorg. Med. Chem. Lett. 2005, 15: 3177-3180. 10.1016/j.bmcl.2005.03.121.View ArticleGoogle Scholar
- Ares JJ, Outt PE, Randall JL, Johnston JN, Murray PD, O'Brien LM, Weisshaar PS, Ems BL: Synthesis and biological evaluation of flavonoids and related compounds as gastroprotective agents. Bioorg. Med. Chem. Lett. 1996, 6: 995-998. 10.1016/0960-894X(96)00134-5.View ArticleGoogle Scholar
- Rojas J, Paya M, Dominguez JN, Ferrandiz ML: The Synthesis and Effect of Fluorinated Chalcone Derivatives on Nitric Oxide Production. Bioorg. Med. Chem. Lett. 2002, 12: 1951-1954. 10.1016/S0960-894X(02)00317-7.View ArticleGoogle Scholar
- Powers DG, Casebier DS, Fokas D, Ryan WJ, Troth JR, Coffen DL: Automated Parallel Synthesis of Chalcone-Based Screening Libraries. Tetrahedron. 1998, 54: 4085-4096. 10.1016/S0040-4020(98)00137-9.View ArticleGoogle Scholar
- Perozo-Rondon E, Martín-Aranda RM, Casal B, Duran-Valle CJ, Lau WN, Zhang XF, Yeung KL: Sonocatalysis in solvent free conditions: An efficient eco-friendly methodology to prepare chalcones using a new type of amino grafted zeolites. Catal. Today. 2006, 114: 183-187. 10.1016/j.cattod.2006.01.003.View ArticleGoogle Scholar
- Lawrence NJ, Rennison D, McGown AT, Ducki S, Gul LA, Hadfield JA, Khan N: Linked Parallel Synthesis and MTT Bioassay Screening of Substituted Chalcones. J. Comb. Chem. 2001, 3: 421-426. 10.1021/cc000075z.View ArticleGoogle Scholar
- Satyanarayana M, Tiwari P, Tripathi BK, Srivastava AK, Pratap R: Synthesis and antihyperglycemic activity of chalcone based aryloxypropanolamines. Bioorg. Med. Chem. 2004, 12: 883-889. 10.1016/j.bmc.2003.12.026.View ArticleGoogle Scholar
- Palleros DR: Solvent-Free Synthesis of Chalcones. J. Chem. Educ. 2004, 81: 1345-1347. 10.1021/ed081p1345.View ArticleGoogle Scholar
- Bu X, Zhao L, Li Y: A Facile Synthesis of 6-C-Prenylflavanones. Synthesis. 1997, 1246-1248. 10.1055/s-1997-1348.Google Scholar
- Sathyanarayana S, Krishnamurthy HG: Corroborative Studies on the Highly Efficient Preparation of 2'-Hydroxychalcones using Partially Dehydarted Barium Hydroxide Catalyst. Curr. Sci. 1988, 57: 1114-1116.Google Scholar
- Sinisterra JV, Garcia-Raso A, Cabello JA, Marians JM: An Improved Procedure for the Claisen-Schmidt Reaction. Synthesis. 1984, 502-503. 10.1055/s-1984-30882.Google Scholar
- Guthrie JL, Rabjhon N: Some Reactions Effected by Means of Bromomagnesium t-Alkoxides. J. Org. Chem. 1957, 22: 176-179. 10.1021/jo01353a022.View ArticleGoogle Scholar
- Rochus W, Kickuth R: Potassium-carbon compounds as catalysts for base catalyzed organic reactions. 1957, German Patent 1 095 832Google Scholar
- Varma RS, Kabalka GW, Evans LT, Pagni RM: Aldol Condensations on Basic Alumina: The Facile Syntheses of Chalcones and Enones in a Solvent-Free Medium. Synth. Commun. 1985, 15: 279-284. 10.1080/00397918508063800.View ArticleGoogle Scholar
- Drexler MT, Amiridis MD: Kinetic Investigation of the Heterogeneous Synthesis of Flavanone over MgO. Catal. Lett. 2002, 79: 175-181. 10.1023/A:1015320711566.View ArticleGoogle Scholar
- Climent MJ, Corma A, Iborra S, Primo J: Base Catalysis for Fine Chemicals Production: Claisen-Schmidt Condensation on Zeolites and Hydrotalcites for the Production of Chalcones and Flavanones of Pharmaceutical Interest. J. Catal. 1995, 151: 60-66. 10.1006/jcat.1995.1008.View ArticleGoogle Scholar
- Guida A, Lhouty MH, Tichit D, Figueras F, Geneste P: Hydrotalcites as base catalysts. Kinetics of Claisen-Schmidt condensation, intramolecular condensation of acetonylacetone and synthesis of chalcone. Appl. Catal., A. 1997, 164: 251-264. 10.1016/S0926-860X(97)00175-0.View ArticleGoogle Scholar
- Sebti S, Solhy A, Tahir R, Boulaajaj S, Mayoral JA, Fraile JM, Kossir A, Oumimoun H: Calcined sodium nitrate/natural phosphate: an extremely active catalyst for the easy synthesis of chalcones in heterogeneous media. Tetrahedron Lett. 2001, 42: 7953-7955. 10.1016/S0040-4039(01)01698-7.View ArticleGoogle Scholar
- Sebti S, Solhy A, Tahir R, Abdelatif S, Boulaajaj S, Mayoral JA, García JI, Fraile JM, Kossir A, Oumimoun H: Application of natural phosphate modified with sodium nitrate in the synthesis of chalcones: a soft and clean method. J. Catal. 2003, 213: 1-6. 10.1016/S0021-9517(02)00017-9.View ArticleGoogle Scholar
- Macquarrie DJ, Nazih R, Sebti S: KF/natural phosphate as an efficient catalyst for synthesis of 2'-hydroxychalcones and flavanones. Green Chem. 2002, 4: 56-59. 10.1039/b109015c.View ArticleGoogle Scholar
- Trivedi JC, Bariwal JB, Upadhyay KD, Naliapara YT, Joshi SK, Pannecouque CC, Clercq ED, Shah AK: Improved and rapid synthesis of new coumarinyl chalcone derivatives and their antiviral activity. Tetrahedron Lett. 2007, 48: 8472-8474. 10.1016/j.tetlet.2007.09.175.View ArticleGoogle Scholar
- Boumendjel A, Boccard J, Carrupt PA, Nicolle E, Blanc M, Geze A, Choisnard L, Wouessidjewe D, Matera EL, Dumontet C: Antimitotic and Antiproliferative Activities of Chalcones: Forward Structure Activity Relationship. J. Med. Chem. 2008, 51: 2307-2310. 10.1021/jm0708331.View ArticleGoogle Scholar
- Petrov O, Ivanova Y, Gerova M: SOCl2/EtOH: Catalytic system for synthesis of chalcones. Catal. Commun. 2008, 9: 315-316. 10.1016/j.catcom.2007.06.013.View ArticleGoogle Scholar
- Sogawa S, Nihro Y, Ueda H, Izumi A, Miki T, Matsumoto H, Satoh T: 3,4-Dihydroxychalcones as potent 5-lipoxygenase and cyclooxygenase inhibitors. J. Med. Chem. 1993, 36: 3904-3909. 10.1021/jm00076a019.View ArticleGoogle Scholar
- Chimenti F, Bizzarri B, Manna F, Bolasco A, Secci D, Chimenti P, Granese A, Rivanera D, Lilli D, Scaltrito MM, Brenciaglia MI: Synthesis and in vitro selective anti-Helicobacter pylori activity of pyrazoline derivatives. Bioorg. Med. Chem. Lett. 2005, 15: 603-607. 10.1016/j.bmcl.2004.11.042.View ArticleGoogle Scholar
- Calloway NO, Green LD: Reactions in the Presence of Metallic Halides. α, β-Unsaturated Ketone Formation as a Side Reaction in Friedel-Crafts Acylations. J. Am. Chem. Soc. 1937, 59: 809-811. 10.1021/ja01284a011.View ArticleGoogle Scholar
- Narender T, Reddy KP: A simple and highly efficient method for the synthesis of chalcones by using borontrifluoride-etherate. Tetrahedron Lett. 2007, 48: 3177-3180. 10.1016/j.tetlet.2007.03.054.View ArticleGoogle Scholar
- Mazza L, Guaram A: An Improved Synthesis of 1,3-Diphenyl-2-buten-1-ones (β-Methylchalcones). Synthesis. 1980, 41-43. 10.1055/s-1980-28916.Google Scholar
- Climent MJ, Garcia H, Primo J: Zeolites as catalysts in organic reactions. Claisen-Schmidt condensation of acetophenone with benzaldehyde. Catal. Lett. 1990, 4: 85-91. 10.1007/BF00764874.View ArticleGoogle Scholar
- Iranpoor N, Kazemi F: RuCI3 Catalyses Aldol Condensations of Aldehydes and Ketones. Tetrahedron. 1998, 54: 9475-9480. 10.1016/S0040-4020(98)00575-4.View ArticleGoogle Scholar
- Shen J, Wang H, Liu H, Sun Y, Liu Z: Brønsted acidic ionic liquids as dual catalyst and solvent for environmentally friendly synthesis of chalcone. J. Mol. Catal. A: Chem. 2008, 280: 24-28. 10.1016/j.molcata.2007.10.021.View ArticleGoogle Scholar
- Konieczny MT, Konieczny W, Sabisz M, Skladanowski A, Wakiec R, Augustynowicz-Kopec E, Zwolska Z: Acid-catalyzed synthesis of oxathiolone fused chalcones. Comparison of their activity toward various microorganisms and human cancer cells line. Eur. J. Med. Chem. 2007, 42: 729-733. 10.1016/j.ejmech.2006.12.014.View ArticleGoogle Scholar
- Deka N, Sarma JC: Microwave-mediated selective monotetrahydropyranylation of symmetrical diols catalyzed by iodine. J. Org. Chem. 2001, 66: 1947-1948. 10.1021/jo000863a.View ArticleGoogle Scholar
- Deka N, Sarma JC: Microwave assisted catalytic protection and deprotection of alcohols with 3,4-dihydro-2h-pyran. Synth. Commun. 2000, 30: 4435-4441. 10.1080/00397910008087070.View ArticleGoogle Scholar
- Kalita DJ, Bora R, Sarma JC: A selective catalytic method of enol-acetylation under microwave Irradiation. J. Chem. Research (S). 1999, 404-405. 10.1039/a902094b.Google Scholar
- Kalita DJ, Bora R, Sarma JC: A new selective catalytic acetalization method promoted by microwave irradiation. Tetrahedron Lett. 1998, 39: 4573-4574. 10.1016/S0040-4039(98)00809-0.View ArticleGoogle Scholar
- Saikia M, Kakati D, Joseph MS, Sarma JC: Iodine-Alumina Catalyzed Aza- Michael Addition under Solvent Free Conditions. Lett. Org. Chem. 2009, 6: 654-658. 10.2174/157017809790442961.View ArticleGoogle Scholar
- Hofer R, Bigorra J: Green chemistry-a sustainable solution for industrial specialties applications. Green Chem. 2007, 9: 203-212. 10.1039/b606377b.View ArticleGoogle Scholar
- Clark JH, Macquarrie DJ: Catalysis of liquid phase organic reactions using chemically modified mesoporous inorganic solids. Chem. Comm. 1998, 853-860. 10.1039/a709143e.Google Scholar
- Perreux L, Loupy A: Microwaves in Organic Synthesis. Edited by: Loupy, A. 2002, Willey-VCH: Weinheim, 61-62.View ArticleGoogle Scholar
- Dallinger D, Kappe CO: Microwave-Assisted Synthesis in Water as Solvent. Chem. Rev. 2007, 107: 2563-2591. 10.1021/cr0509410.View ArticleGoogle Scholar
- Sashidhara KV, Rosaiah JN, Kumar A: Iodine-Catalyzed Mild and Efficient Method for the synthesis of Chalcones. Synth. Commun. 2009, 39: 2288-2296. 10.1080/00397910802654724.View ArticleGoogle Scholar
- Khupse RS, Erhardt PW: Total Synthesis of Xanthohumol. J. Nat. Prod. 2007, 70: 1507-1509. 10.1021/np070158y.View ArticleGoogle Scholar
- Deka N, Sarma JC: Highly efficient dithioacetalization of carbonyl compounds catalyzed with iodine supported on neutral alumina. Chem. Lett. 2001, 794-795. 10.1246/cl.2001.794.Google Scholar
- Montes-Avila J, Diaz-Camacho SP, Sicairos-Felix J, Delgado-Vargas F, Rivero IA: Solution-phase parallel synthesis of substituted chalcones and their antiparasitary activity against Giardia lamblia. Bioorg. Med. Chem. 2009, 17: 6780-6785. 10.1016/j.bmc.2009.02.052.View ArticleGoogle Scholar