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Synlett 2003(6): 0858-0860
DOI: 10.1055/s-2003-38734
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

One-Pot Synthesis of Dihydropyrimidinones Using Iodotrimethylsilane. Facile and New Improved Protocol for the Biginelli Reaction at Room Temperature [1]

Gowravaram Sabitha*, G. S. Kiran Kumar Reddy, Ch. Srinivas Reddy, J. S. Yadav
Organic Chemical Sciences, Indian Institute of Chemical Technology, Hyderabad-500 007, India
Fax: +91(40)27160512; e-Mail: sabitha@iict.ap.nic.in;
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Publication History

Received 19 December 2002
Publication Date:
17 April 2003 (online)

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Abstract

A novel one pot condensation of an aldehyde, β-ketoester and urea has been performed using TMSI in acetonitrile for the first time at room temperature affording dihydropyrimidinones in excellent yields.

Key words

Biginelli reaction - dihydropyrimidinones - iodotrimethyl silane - one-pot condensation - room temperature

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IICT Communication No. 01/10/03.

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IICT Communication No. 01/10/03.

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One-Pot Synthesis of Dihydropyrimidinone. Typical Procedure: TMSCl (8 mmol) was added to a stirred mixture of benzaldehyde (10 mmol), β-ketoester (10 mmol), urea (12 mmol), and NaI (8 mmol) in MeCN at r.t. Immediately the solid product precipitated out and the reaction was complete in 30 min as monitored by TLC. The precipitate was filtered and the product was washed with 20% EtOAc in hexane to give pure dihydropyrimidinone 4a in 98% yield. Spectral data for selected compounds. 4b: Mp 205-206 °C. 1H NMR (200 MHz, DMSO-d 6): δ = 1.00 (t, 3 H, J = 8.0 Hz), 2.40 (s, 3 H), 3.90 (q, 2 H, J = 8.0 Hz), 5.80 (sd, 1 H, J = 3.0 Hz), 6.42 (br s, NH), 7.38-7.68 (m, 3 H, ArH), 7.82 (d, 1 H, J = 8.5 Hz, ArH), 9.20 (br s, NH). IR (KBr): 1592, 1652, 1705, 1720, 2983, 3238 cm-1. 4h: Mp 207-208 °C. 1H NMR (200 MHz, CDCl3): δ = 1.20 (t, 3 H, J = 8.5 Hz), 2.25 (s, 3 H), 4.10 (q, 2 H, J = 8.5 Hz), 5.55 (sd, 1 H, J = 3.5 Hz), 6.80-7.00 (m, 2 H, ArH), 7.10 (m, 1 H), 7.40 (br s, NH), 9.00 (br s, NH). IR (KBr): 1695, 1715, 3240 cm-1. 4i: Mp 195-196 °C. 1H NMR (300 MHz, DMSO-d 6): δ = 0.75 (d, 3 H, J = 6.2 Hz), 0.90 (d, 3 H, J = 6.2 Hz), 1.25 (t, 3 H, J = 7.0 Hz), 1.75 (m, 1 H), 2.25 (s, 3 H), 4.0 (t, 1 H, J = 3.5 Hz), 4.05 (q, 2 H, J = 8.5 Hz), 7.0 (br s, NH), 8.80 (br s, NH).
IR (KBr): 1650, 1700, 3109, 3245 cm-1. 4k: Mp 206-207 °C. 1H NMR (200 MHz, DMSO-d 6): δ = 1.15 (t, 3 H, J = 7.0 Hz), 2.30 (s, 3 H), 4.05 (q, 2 H, J = 7.0 Hz), 5.22 (sd, 1 H, J = 3.5 Hz), 7.25 (m, 4 H, ArH), 7.70 (s, 1 H), 9.30 (br s, NH), 9.95 (br s, NH). IR (KBr): 1585, 1672, 3100, 3185, 3338 cm-1. 6a: Mp 161-163 °C. 1H NMR (200 MHz, DMSO-d 6): δ = 0.90 (t, J = 7.1 Hz, 3 H), 2.99 (d, J = 10.7 Hz, 1 H), 3.85 (q, J = 7.1 Hz, 1 H), 4.85 (d, J = 10.7 Hz, 1 H), 6.95 (br s, NH), 7.15 (br s, NH). IR (KBr): 1685, 1710, 3200, 3450 cm-1.