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Synlett 2006(19): 3309-3313  
DOI: 10.1055/s-2006-951555
LETTER
© Georg Thieme Verlag Stuttgart · New York

Gold-Catalyzed Cyclization of O-Propargyl Carbamates under Mild ­Conditions: A Convenient Access to 4-Alkylidene-2-oxazolidinones

Stefanie Ritter, Yoshikazu Horino, Johann Lex, Hans-Günther Schmalz*
University of Cologne, Institute of Organic Chemistry, Greinstr. 4, 50939 Köln, Germany
Fax: +49(221)4703064; e-Mail: schmalz@uni-koeln.de;
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Publikationsverlauf

Received 20 July 2006
Publikationsdatum:
23. November 2006 (online)

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Abstract

On treatment with catalytic amounts of gold(I) chloride (AuCl) and a base co-catalyst, O-propargyl carbamates smoothly undergo a 5-exo-dig cyclization at room temperature to afford 4-methylene-2-oxazolidinones in high yield. Substrates with a sub­stituent at the alkyne terminus stereoselectively give rise to (Z)-4-alkylidene-2-oxazolidinones.

Key words

oxazolidinones - heterocycles - gold catalysis - alkynes

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Crystal data for compound 9a: colorless crystals (from cyclohexane); mp 87-88 °C; C16H19NO4S, FW = 321.10, triclinic, space group P-1; a = 7.2854 (2) Å, b = 8.7222 (3) Å, c = 12.7763 (4) Å; α = 96.866 (2)°, β = 100.075 (2)°, γ = 99.598 (2)°; V = 778.85 (4) Å3; Z = 2; d calc = 1.370 g/cm3; R = 0.0391, R w = 0.0837 for 2517 reflections having I > 2σ(I). Further crystallographic data have been deposited at the Cambridge Crystallographic Data Centre. Copies of the data (CCDC 613241) can be obtained free of charge from CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: +44 (1223)336033; e-mail: deposit@ccdc.cam.ac.uk].

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General Procedure for the AuCl-Catalyzed Cyclization of O -Propargyl Carbamates: To a solution of an O-propargyl carbamate (6 or 8a-8f; 0.5 mmol) and a base co-catalyst (0.025 mol, 5 mol%) in solvent (2 mL) was added AuCl (0.025 mol, 5 mol%). The mixture was stirred at r.t. or 60 °C for the time specified in Tables [2] and [3] . Conversion was monitored by TLC and/or GLC analyses. The reaction mixture was filtered through a small pad of Celite® (elution with CH2Cl2). Removal of the solvent under reduced pressure and purification of the residue by flash chromatog-raphy on SiO2 (cyclohexane-EtOAc, 3:1) afforded the products (7 or 9) as colorless oils or solids.
4-Methylene-3-(toluene-4-sulfonyl)-1-oxa-3-azaspiro[4.5]decan-2-one ( 9a): 1H NMR (300 MHz, CDCl3): δ = 1.34-1.74 (m, 10 H), 2.41 (s, 3 H), 4.39 (d, 2 J = 3 Hz, 1 H, C=CH), 5.46 (d, 2 J = 3 Hz, 1 H, C=CH), 7.31 (d, 3 J = 8.3 Hz, 2 H), 7.89 (d, 3 J = 8.3 Hz, 2 H). 13C NMR (75 MHz, CDCl3): δ = 21.36 (t), 21.65 (q), 24.28 (t), 36.64 (t), 84.83 (s), 90.14 (t), 127.92 (d), 129.75 (d), 134.31 (s), 144.96 (s), 145.94 (s), 150.26 (s). IR (ATR): 1782 (ss, C=O), 1660 (s, C=C) cm-1. MS (DIP-EI, 70 eV): m/z (%) = 321 [M+], 166 (14), 155 (24), 105 (12), 94 (23), 91 (100), 81 (16), 65 (33). HRMS (EI): m/z [M]+ calcd for 12C16H19 14N16O4 32S: 321.1035; found: 321.104.
( Z )-4-Ethylidene-3-tosyloxazolidin-2-one ( 9b): 1H NMR (250 MHz, CDCl3): δ = 1.85 (td, 5 J = 1.8 Hz, 3 J = 7.36 Hz, 3 H, CH3), 2.42 (s, 3 H), 4.62 (app pent, 2 H,), 5.24 (tq, 4 J = 1.8 Hz, 3 J = 7.4 Hz, 1 H), 7.33 (d, 3 J = 8 Hz, 2 H), 7.92 (d, 3 J = 8 Hz, 2 H). Characteristic signals of the minor isomer iso-9b: 1H NMR (250 MHz, CDCl3): δ = 4.56 (dt, 5 J t = 1 Hz, 3 J d = 6 Hz, 2 H), 5.43 (tq, 4 J q = 1 Hz, 3 J t = 5 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 14.63 (q), 21.75 (q), 70.14 (t), 112.43 (q), 128.28 (d), 129.87 (d), 135.4 (s), 138.84 (s), 145.77 (s), 153.54 (s, C=O). IR (ATR): 2923 (w, C=CCH3), 1782 (ss, C=O) cm-1. MS (DIP-EI, 70 eV): m/z (%) = 267 [M+], 155 (34), 112 (11), 95 (32), 91 (100), 65 (23), 57 (44). HRMS (EI): m/z [M]+ calcd for 12C12H13 14N16O4 32S: 267.0565; found: 267.056.
( Z )-4-Benzylidene-3-(toluene-4-sulfonyl)oxazolidin-2-one ( 9c): 1H NMR (250 MHz, CDCl3): δ = 2.42 (s, 3 H), 4.82 (d, 4 J = 2 Hz, 2 H), 6.15 (t, 4 J = 2 Hz, 1 H), 7.25-7.31 (m, 7 H), 7.68 (d, 3 J = 8.5 Hz, 2 H). 13C NMR (75 MHz, CDCl3): δ = 21.71 (q), 70.28 (t), 115.87 (d), 127.13 (s), 127.79 (d), 128.48 (d), 128.54 (d), 129.57 (d), 134.49 (s), 134.80 (s), 145.76 (s), 153.90 (s, C=O). IR (ATR): 3058 (w, C=CR), 1788 (ss, C=O) cm-1. MS (DIP-EI, 70 eV): m/z (%) = 329 [M+], 174 (12), 155 (33), 130 (68), 103 (25), 91 (100), 77 (26), 65 (31), 51 (9). HRMS (EI): m/z [M]+ calcd for 12C17H15 14N16O4 32S: 321.0721; found: 321.072.
4-Methylene-3-phenyloxazolidin-2-one ( 9d): 1H NMR (250 MHz, CDCl3): δ = 4.12 (d, 2 J = 2.5 Hz, 1 H, C=CH), 4.21 (d, 2 J = 2.5 Hz, 1 H, C=CH), 5.01 (t, 2 J = 2 Hz, 2 H), 7.30-7.46 (m, 5 H). 13C NMR (75 MHz, CDCl3): δ = 67.10 (t), 82.00 (t), 126.91 (d), 128.94 (d), 129.15 (d), 133.55 (s), 141.72 (s), 155.97 (s, C=O). IR (ATR): 1757 (ss, C=O), 1680 (s, C=CH) cm-1. MS (DIP-EI, 70 eV): m/z (%) = 175 [M+], 130 (100), 103 (56), 91 (8), 77 (68), 63 (10), 51 (46). HRMS (EI): m/z [M]+ calcd for 12C10H9 14N16O2: 175.0633; found: 175.063.
( Z )-4-Ethylidene-3-phenyloxazolidin-2-one ( 9e): 1H NMR (250 MHz, CDCl3): δ = 1.06 (td, 5 J = 2.3 Hz, 3 J = 7.3 Hz, 3 H), 4.47 (tq, 4 J = 2.3 Hz, 3 J = 7.3 Hz, 1 H), 4.91 (m, 2 H), 7.30-7.43 (m, 5 H). 13C NMR (75 MHz, CDCl3): δ = 10.43 (q), 66.06 (t), 93.17 (d), 127.09 (d), 127.17 (d), 128.21 (d), 128.59 (d), 129.55 (d), 129.87 (d), 130.59 (s), 135.16 (s). IR (ATR): 1771 (ss, C=O), 1699 (s, C=CH) cm-1. MS (DIP-EI, 70 eV): m/z (%) = 207 [M+], 189 (32), 149 (33), 132 (36), 119 (100), 104 (27), 91 (29), 84 (74), 77 (69), 57 (77), 49 (94). HRMS (EI): m/z [M]+ calcd for 12C11H11 14N16O2: 189.079; found: 189.079.
( Z )-4-Benzylidene-3-phenyloxazolidin-2-one ( 9f): 1H NMR (300 MHz, CDCl3): δ = 5.10 (d, 4 J = 2.1 Hz, 2 H), 5.67 (s, 1 H), 6.63 (d, J = 1.7 Hz, 2 H), 6.81-6.90 (m, 3 H), 6.98-7.06 (m, 5 H). 13C NMR (75 MHz, CDCl3): δ = 68.03 (t), 99.89 (t), 125.88 (d), 126.96 (d), 128.12 (d), 128.16 (d), 128.68 (d), 129.74 (d), 132.27 (s), 132.83 (s), 134.60 (s), 156.95 (s, C=O). IR (ATR): 3053 (w, C=CR), 1769 (ss, C=O) cm-1. MS (DIP-EI, 70 eV): m/z (%) = 251 [M+], 206 (23), 104 (100), 89 (9), 77 (32), 63 (8), 51 (22). HRMS (EI): m/z [M]+ calcd for 12C16H13 14N16O2: 251.0946; found: 251.094.