Synlett 2007(2): 0215-0218  
DOI: 10.1055/s-2007-967997
LETTER
© Georg Thieme Verlag Stuttgart · New York

A New Organocatalytic Process of Cyclotrimerization of Acetylenic Ketones Mediated by 2,4-Pentanedione

Qing-Fa Zhou, Fei Yang, Qing-Xiang Guo, Song Xue*
Department of Chemistry, University of Science and Technology of China, Hefei, 230026, P. R. of China
Fax: +86(551)3606689; e-Mail: xuesong@ustc.edu.cn;
Further Information

Publication History

Received 24 September 2006
Publication Date:
24 January 2007 (online)

Abstract

A new organocatalytic process of cyclotrimerization of the aliphatic and aromatic acetylenic ketones was developed. The reaction catalyzed by DMAP in the presence of 2,4-pentanedione gave 1,3,5-trisubstituted benzenes in almost quantitative yields ­under very mild conditions. 2,4-Pentanedione was used as a co-­catalyst to promote the reaction efficiently, particularly for aliphatic acetylenic ketones.

10

Typical Procedure.
A round-bottomed flask, equipped with a stirring bar, was charged with 2,4-pentanedione (0.15 mmol) and acetylenic ketone (0.3 mmol) dissolved in CH2Cl2 (2 mL) followed by DMAP (0.03 mmol). The reaction was run at r.t. for the indicated time (monitored by TLC). The reaction was concentrated under reduced pressure on a rotary evaporator and purified by silica gel chromatography using PE-EtOAc (10:1 to 3:1).
Compound 3a: 1H NMR (300 MHz, CDCl3): δ = 8.63 (s, 3 H), 2.64 (s, 9 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 196.7, 138.0, 131.8, 26.9 ppm. IR (KBr): ν = 1690, 1227 cm-1. HRMS (EI): m/z calcd for C12H12O3 [M]+: 204.0786; found: 204.0791.
Compound 3b: 1H NMR (300 MHz, CDCl3): δ = 8.56 (s, 3 H), 7.25-7.10 (m, 15 H), 3.31 (t, J = 7.5 Hz, 6 H), 3.03 (t, J = 7.5 Hz, 6 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 197.9, 140.8, 137.8, 131.3, 128.7, 128.6, 126.4, 40.8, 30.1 ppm. IR (KBr): ν = 1694, 1162 cm-1. HRMS (EI): m/z calcd for C33H30O3 [M]+: 474.2195; found: 474.2192.
Compound 6: 1H NMR (300 MHz, CDCl3): δ = 8.49 (d, J = 1.5 Hz, 2 H), 8.29 (d, J = 1.5 Hz, 1 H), 7.76 (d, J = 7.6 Hz, 4 H), 7.57-7.54 (m, 2 H), 7.47-7.42 (m, 4 H), 2.63 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 195.4, 193.9, 137.4, 136.4, 135.4, 133.8, 132.2, 131.5, 129.0, 127.6, 25.8 ppm. IR (KBr): ν = 1691, 1662, 1242 cm-1. HRMS (EI): m/z calcd for C22H16O3 [M]+: 328.1099; found: 328.1092.