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Synlett 2003(11): 1639-1642
DOI: 10.1055/s-2003-41420
LETTER
© Georg Thieme Verlag Stuttgart · New York

Lewis Acid-Catalyzed Reaction of Allenes with Activated Ketone

Bo Xu, Min Shi*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, P. R. of China
Fax: +86(21)64166128; e-Mail: mshi@pub.sioc.ac.cn.;
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Publication History

Received 19 June 2003
Publication Date:
22 September 2003 (online)

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Abstract

Allenes react with activated ketone to give the corresponding addition products in good yields and good stereoselectivities in the presence of Lewis acid Yb(OTf)3 and acetic anhydride or acetyl chloride as a quencher under mild reaction conditions.

Key words

allenes - Lewis acid - activated ketone - acetic anhydride - acetyl chloride

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The X-ray crystal data of 3 has been deposited in CCDC with number 208298. Empirical Formula: C14H14O5. Formula weight: 262.25. Crystal color, habit: colorless, prismatic. Crystal dimensions: 0.267 × 0.251 × 0.189 mm. Crystal system: monoclinic. Lattice type: primitive. Lattice parameters: a = 7.9550(8) Å, b = 9.5303 (9) Å, c = 17.5333 (17) Å, α = 90°, β = 98.933 (2)°, γ = 90°, V = 1313.1 (2) Å3. Space group: P2 (1)/n; Z value = 4; D calc = 1.327 g/cm3; F 000 = 552. Diffractometer: Rigaku AFC7R; Residuals: R1; wR2: 0.0413, 0.0722.

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Typical Procedure for the Reaction of Allenes with an Activated Ketone: Under argon atmosphere, allene 1a (58 mg, 0.5 mmol), Yb(OTf)3 (0.0025 mmol) and mesoxalate 2 (139 mg, 0.8 mmol), acetyl chloride (1.5 mmol) was dissolved in 1.5 mL of CH2Cl2, the reaction mixture was stirred for 18 h at r.t., then the reaction was quenched with aq. NaHCO3 solution. The organic layer was washed with H2O and dried over MgSO4. The solvent was removed under reduced pressure and the residue was purified by passing through a silica gel column chromatography (SiO2, hexane/EtOAc = 10/1 as an eluent) to afford adducts 5a (156 mg) as a colorless oil, yield 85%. IR (neat): 2893, 1754, 1446, 1241, 1055, 912 cm-1. 1H NMR (300 MHz, CDCl3, TMS): δ = 1.32 (t, J = 7.2 Hz, 6 H), 2.28 (s, 3 H), 4.30 (q, J = 7.2 Hz, 4 H), 4.43 (s, 2 H), 7.10 (s, 1 H), 7.34-7.48 (m, 5 H, Ar). 13C NMR (75 MHz, CDCl3): δ = 13.70, 20.52, 39.26, 62.55, 82.33, 128.41, 128.55, 128.69, 130.38, 134.40, 136.10, 165.07, 169.22. MS (EI): m/z = 368, 333, 308, 273, 235, 199, 143, 115. HRMS (EI): Calcd for C18H21ClO6 (M+): 368.1027. Found: 368.1026.