Synlett 2009(18): 2971-2976  
DOI: 10.1055/s-0029-1218280
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Temperature-Controlled Selectivity toward [1,3]- or [3,3]-Sigmatropic Rearrangement: Regioselective Synthesis of Substituted 3,4-Dihydrocoumarins

Yunkui Liu*, Jianqiang Qian, Shaojie Lou, Zhenyuan Xu*
State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014, P. R. of China
e-Mail: ykuiliu@zjut.edu; e-Mail: greensyn@zjut.edu.cn;
Further Information

Publication History

Received 21 July 2009
Publication Date:
08 October 2009 (online)

Abstract

Either [1,3]- or [3,3]-sigmatropic rearrangements were selectively accessed by controlling the reaction temperature in the gold(III)-catalyzed tandem rearrangement/cyclization of (E)-2-(aryloxymethyl)alk-2-enoates to afford diversely substituted 3,4-dihydrocoumarin derivatives in moderate to good yields and in excellent regioselectivity.

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Typical Experimental Procedure for the Synthesis of 2 under Condition A: AuCl3 (9.1 mg, 0.03 mmol), AgOTf (23.1 mg, 0.09 mmol), and DCE (2 mL) were added to a 10-mL flask. The mixture was stirred at r.t. for 5 min before a DCE solution of 1a (0.35 g, 1.0 mmol diluted in 1 mL of solvent) was added. Then the reaction mixture was stirred at 80 ˚C for 4 h. Upon completion of the reaction, the resulting mixture was diluted with CH2Cl2 (10 mL) and filtered through Celite. After evaporation of the solvent under vacuum, the residue was purified by column chromatog-raphy on silica gel (200-300 mesh) using cyclohexane-EtOAc (12:1) as eluent to give pure 2a.
Typical Experimental Procedure for the Synthesis of 3 under Condition B: AuCl3 (9.1 mg, 0.03 mmol), AgOTf (23.1 mg, 0.09 mmol), and DCE or DCB (2 mL) were added to a 10-mL sealed vessel. The mixture was stirred at r.t. for 5 min before a DCE or DCB solution of 1a (0.35 g, 1.0 mmol diluted in 1 mL of solvent) was added. Then the reaction mixture was stirred at 120 ˚C for 2 h. Upon completion of the reaction, the resulting mixture was diluted with CH2Cl2 (10 mL) and filtered through Celite. After evaporation of the solvent under vacuum, the residue was purified by column chromatography on silica gel (200-300 mesh) using cyclohexane-EtOAc (12:1) as eluent to give pure 3a.

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Representative Data for Compound 2 and 3:
Compound 2b: white solid; R f 0.46 (cyclohexane-EtOAc, 12:1); mp 198.3-201.0 ˚C. ¹H NMR (500 MHz, CDCl3): δ = 4.32 (d, 2 H, J = 2.5 Hz, CH2), 7.25 (d, 1 H, J = 8.5 Hz, ArH), 7.43-7.85 (m, 9 H, ArH), 8.03 (t, 1 H, J = 2.5 Hz, ArCH=). ¹³C NMR (125 MHz, CDCl3): δ = 26.12, 112.14, 117.50, 122.28, 122.91, 124.27, 125.25, 127.33, 128.87, 129.25, 130.76, 130.91, 131.74, 132.17, 133.55, 142.13, 147.77, 163.60. IR (KBr): 1711 (C=O), 1630 (C=C) cm. GC-MS: m/z = 364 [M+], 366 [M+ + 2]. HRMS (EI): m/z calcd for C20H13O2Br: 364.0099; found: 364.0113.
Compound 3c: white solid; R f 0.56 (cyclohexane-EtOAc, 12:1); mp 114.5-114.6 ˚C. ¹H NMR (500 MHz, CDCl3): δ = 2.28 (s, 3 H, Me), 4.90 (s, 1 H), 5.72 (s, 1 H), 6.44 (s, 1 H), 6.89-7.33 (m, 8 H, ArH). ¹³C NMR (125 MHz, CDCl3): δ = 20.80, 48.26, 117.04, 124.28, 127.52, 127.76, 128.96, 129.08, 129.26, 129.43, 134.53, 136.88, 140.77, 148.59, 163.26. IR (KBr): 1746 (C=O), 1627 (C=C) cm. GC-MS: m/z = 250 [M+]. HRMS (EI): m/z calcd for C17H14O2: 250.0994; found: 250.1001.