Synlett 2010(16): 2513-2517  
DOI: 10.1055/s-0030-1258551
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

N-Heterocyclic Carbene Catalyzed Vinylogous Aldol Reaction of 2-(Trimethylsilyloxy)furan and Aldehydes

Guang-Fen Du, Lin He*, Cheng-Zhi Gu, Bin Dai
School of Chemistry and Chemical Engineering, Shi He Zi University, Xin Jiang 832000, P. R. of China
Fax: +86(993)2057270; e-Mail: helin@shzu.edu.cn;
Further Information

Publication History

Received 18 June 2010
Publication Date:
03 September 2010 (online)

Abstract

A N-Heterocyclic carbenes (NHC) catalyzed vinylogous aldol reaction between 2-(trimethylsilyloxy)furan and aldehydes has been developed, providing γ-substituted butenolides in high yields with good diastereoselectivities. Furthermore, the catalyst loading can be reduced to 1 mol%.

20

General Procedure for NHC-Catalyzed Vinylogous Aldol Reaction of 2-(Trimethylsilyloxy)furan with Aldehydes
To a solution of 2 (4.0 mg, 0.012 mmol) in anhyd THF (2.0 mL) was added KOt-Bu (1.1 mg, 0.01 mmol) under N2. After stirred for 30 min at r.t., the solution was then cooled to 0 ˚C and aldehyde (1.0 mmol) was added followed by 2-(trimethylsilyloxy)furan (1.3 mmol, 200 µL). The reaction mixture was then stirred at r.t. until full consumption of the starting aldehyde as indicated by TLC. The solution was then cooled to 0 ˚C and quenched with 10% aq HCl. The mixture was stirred for 30 min and neutralized by sat. aq NaHCO3 and then extracted with EtOAc. The combined organic phase was dried over anhyd Na2SO4, filtered, and concentrated. The ratio of anti/syn was determined by ¹H NMR analysis of the crude products, and the configurations were assigned by ¹H NMR comparison with literature data. The crude products were purified through silica gel chromatography (EtOAc-PE) to afford pure anti products or a mixture of anti/syn isomers.
Data for 8g Yield 83%; white solid; R f  = 0.14 (PE-EtOAc, 4:1); mp 134.5-135.5 ˚C. ¹H NMR (400 MHz, CDCl3): δ = 7.61 (dd, J = 7.6, 1.2 Hz, 1 H), 7.20-7.45 (m, 4 H), 6.20 (dd, J = 5.6, 2.0 Hz, 1 H), 5.62 (t, J = 4.0 Hz, 1 H), 5.36-5.44 (m, 1 H), 3.36 (d, J = 4.4 Hz, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 172.3, 151.2, 134.5, 130.8, 128.6, 126.9, 126.4, 122.5, 83.6, 68.4. IR (KBr): ν = 3390, 1726, 1465, 1437, 1342, 1188, 1108, 1025, 918, 819, 744, 609 cm. ESI-HRMS: m/z calcd for C11H9ClO3Na: 247.0132; found: 247.0156.