Indian Journal of Chemistry Vol. 53B, January 2014, pp 124-126 An improved procedure of Miyashita protocol for the preparation of ureidomethylene derivatives of 1,3-dicarbonyl compounds A Majee*, S K Kundu, S Santra & A Hajra Department of Chemistry, Visva-Bharati (A Central University), Santiniketan 731 235, India E-mail: [email protected] Received 12 July 2012; accepted (revised) 8 September 2013 A facile method has been developed for the synthesis of ureidomethylene derivatives by the condensation of 1,3-dicarbonyl compounds, urea and trimethylorthoformate in presence of Zn(OTf)2 under solvent-free conditions. A variety of 1,3-dicarbonyl compounds undergo this reaction to yield the corresponding ureidomethylene derivatives in good yields. Methyl substituted ureas also give the condensation product under similar reaction conditions. Keywords: 1,3-Diones, urea, trimethyl orthoformate, zinc triflate, solvent-free Miyashita et al1 reported the synthesis of uracil Results and Discussions derivatives by condensation of diethyl malonate, urea Over the years efforts are focused towards the and triethyl orthoformate followed by treatment of introduction of better methodologies3 in organic base with the intermediate 2-ureidomethylene- synthesis. Here, the Miyashita protocol has been malonic acid diethyl ester. W D Jones Jr2 used the selected for the synthesis of ureidomethylene same condensation of 1,3-dicarbonyl compound, derivatives. In the present technique the condensation powdered urea and trimethyl orthoformate at 140°C of 1,3-dicarbonyl compounds (1 mmol), urea following this Miyashita protocol to get the same (1.5 mmol) and trimethylorthoformate (1 mmol) has condensed product 2-ureidomethylene-malonic acid been carried out in presence of Zn(OTf)2 (5 mol%) Scheme I diethyl ester. Although this method is quite useful for under solvent-free conditions ( ). It has been observed that the yield of the product can be enhanced the preparation of the ureidomethylene derivatives, to 78-85% in place of 45-66% in presence of however the reported yields are within 45-66% only. Zn(OTf) (5 mol%) under the solvent-free conditions et al2 synthesized 2 Using this intermediate Jones, Jr at RT. 5- and 6-acyl-2(1H)-pyrimidones whereas uracil To optimize the reaction conditions, the condensation derivatives have also been synthesized by Miyashita 1 of acetylacetone, urea and trimethylorthoformate was et al . Accordingly, they have not given much selected as a model to examine the effects of the importance to improve the yield or to modify the catalyst (0-10 mol%) and temperature. The best result reaction conditions towards a lower temperature. So, was achieved by carrying out the reaction with to improve the yield of this ureidomethylene 1:1.5:1 mole ratios of acetylacetone, urea and intermediate under simpler reaction conditions is of trimethyl-orthoformate in the presence of 5 mol% great interest as the overall yield of the reaction is Zn(OTf)2. Higher amount of the catalyst did not dependent on the intermediate. improve the results to a great extent. A wide range of O O O O O 1 2 R R + Zn(OTf)2 CH(OMe)3 + H N NH R1 R2 2 2 RT H NH 1 2 3 O NH2 4a-f Scheme I Scheme I MAJEE et al.: IMPROVED MIYASHITA PROTOCOL 125 structurally diverse 1,3-dicarbonyl compounds was delightful to observe that the product was underwent this reaction to provide ureidomethylene obtained in good yields without formation of any side derivatives in good yields. From the results it is products (Scheme III). obvious that this procedure is equally efficient for all Finally, the focus was turned toward the possibility the dicarbonyl compounds. The results are of using methyl substituted trimethylorthoformate summarized in Table I. (1,1,1-trimethoxyethane) and phenyl substituted The reaction proceeds very well with cyclic trimethylorthofomate (trimethoxymethyl-benzene) but dicarbonyl compound like 5,5-dimethyl-cyclohexane- unfortunately, enamine was found as the sole product 1,3-dione under the present reaction conditions in both the cases (Scheme IV). (Scheme II). Two 1,3-dicarbonyl systems have been used in In addition, the capacity and effectiveness of the addition to substituted trimethyl orthoformate but reaction was explored for the substituted urea and it each time only the enamines were obtained which are summarized in Table II. Table I — Synthesis of uriedomethylene derivatives Entry R1 R2 Time Product Yield Experimental Section (hr) (%)a Melting points were determined on a glass disk with an electrical bath and are uncorrected. 1H NMR 1 CH CH 7.5 4a 85 3 3 (300 MHz) and 13C NMR (75 MHz) spectra were 2 CH3 OCH2CH3 8 4b 85 recorded in CDCl3 solutions. IR spectra were taken as 3 CH3 OCH3 8 4c 83 KBr pellets in a Shimadzu 8400S FTIR instrument. 4 CH3 OC(CH3)3 9 4d 78 All the products were characterized by comparing 5 CH3 OAllyl 7.5 4e 78 with authentic samples and the spectral data of the 6 OCH2CH3 OCH2CH3 7 4f 80 compounds which has not been reported in literature aIsolated yield. are given in the supporting information. O Zn(OTf)2 + O O CH(OMe)3 + H N NH 2 2 7h, RT OO H NH 5 2 3 O NH2 6 (85%) Scheme II O O O O O Zn(OTf)2 O + CH(OMe)3 + H2NN OCH2CH3 H 8h, RT H NH 7 2 8 O N H 9 (56%) Scheme III 3 O O O R 4 Zn(OTf)2 + R C(OMe) + 3 H N NH R3 2 2 8h, RT O HN O NH 10 11 3 2 12a-d Scheme IV 126 INDIAN J. CHEM., SEC B, JANUARY 2014 Table II — Synthesis of enamine derivatives Conclusions 3 4 a In conclusion, a simple and efficient methodology Entry R R Time (hr) Product Yield (%) has been developed for the synthesis of 1 OCH2CH3 CH3 8 12a 82 ureidomethylene derivatives through a three- 2 OAllyl CH3 7 12b 84 component condensation reaction under solvent-free 3 OCH2CH3 Ph 8 12c 83 conditions. The non-hazardous experimental 4 OAllyl Ph 8 12d 78 conditions, ease of reaction and high yields are the aIsolated yield. notable advantages of this procedure. Thus, it provides a better and more practical alternative to the existing Miyashita protocol. Typical procedure for synthesis of (2-acetyl-3-oxo- but-1-enyl)-urea, 4a Acknowledgments In a typical experimental procedure, a mixture of AM and AH acknowledge financial support from acetylacetone (1 mmol, 100 mg), urea (1.5 mmol, 90 CSIR (Grant No. 01(2251)/08/EMR-II). SS thanks the mg) and trimethylorthoformate (1 mmol, 106 mg) was UGC for his fellowship. The authors are thankful to taken in presence of Zn(OTf)2 (5 mol%, 18 mg) in a DST-FIST and UGC-SAP. round bottom flask fitted with a guard tube under atmospheric pressure (no need of inert atmosphere) References and was stirred at RT until the whole mixture was 1 Jones W D Jr, Huber E W, Grisar J M & Schnettler R A, solidified. After completion of the reaction J Heterocycl Chem, 24, 1987, 1221. 2 Miyashita O, Matsumura K, Shimadzu H & Hashimoto N, (solidification), methanol was evaporated and the Chem Pharm Bull, 29, 1981, 3181. reaction mixture was extracted from ethyl acetate- 3 (a) Santra S, Majee A & Hajra A, Tetrahedron Lett, 52, water mixture. The organic layer was dried over 2011, 3825; (b) Santra S, Majee A & Hajra A, Tetrahedron anhydrous Na SO and on evaporation of solvent Lett, 53, 2012, 1974; (c) Kundu D, Majee A & Hajra A, 2 4 Chemistry-An Asian Journal, 6, 2011, 406; (d) Kundu D, under reduced pressure, the solid crude product was Bagdi A K, Majee A & Hajra A, Synlett, 2011, 1165; (e) obtained. The crude product was purified by washing Kundu D, Majee A & Hajra A, Catal Commun, 11, 2010, with ether to obtain the desired compound in good 1157; (f) Rahman M, Kundu D, Hajra A & Majee A, ° Tetrahedron Lett, 51, 2010, 2896; (g) Kundu D, Debnath R yield (145 mg, 85%). m.p. 181-82 C, IR (KBr): 3309, K, Majee A & Hajra A, Tetrahedron Lett, 50, 2009, 6998; (h) -1 1 1620, 1558, 1411, 1228, 1157 cm ; H NMR: δ 11.35 Rahman M, Roy A, Majee A & Hajra A, J Chem Res, 2009, (d, J = 12Hz, 1H, NH), 8.21 (d, J = 12Hz, 1H), 7.50 178; (i) Urinda S, Kundu D, Majee A & Hajra A, J Het Atom, 20, 2009, 232; (j) Kundu D, Majee A & Hajra A, (s, br, 1H, NH2), 6.00 (s, br, 1H), 2.23 (s, 3H), 2.13 (s, 13 δ Tetrahedron Lett, 50, 2009, 2668; (k) Roy A, Rahman M, 3H); C NMR: 200.28, 196.02, 153.58, 149.25, Das S, Kundu D, Kundu S K, Majee A & Hajra A, Synth 114.83, 31.57, 26.64. Commun, 39, 2009, 590. .