Synlett 2018; 29(10): 1319-1323
DOI: 10.1055/s-0036-1591756
letter
© Georg Thieme Verlag Stuttgart · New York

High-Pressure Au-Catalyzed Cycloisomerization of Internal 1,6- and 1,7-Enynes

Małgorzata Kocój
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Email: wojciech.chaladaj@icho.edu.pl
,
Elżbieta Jarosińska
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Email: wojciech.chaladaj@icho.edu.pl
,
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Email: wojciech.chaladaj@icho.edu.pl
› Author Affiliations
Financial support from the Polish National Science Centre (Grant decision DEC-2013/11/D/ST5/02979) and the Polish Ministry of Science and Higher Education (stipend for W.C.) is gratefully acknowledged.
Further Information

Publication History

Received: 28 October 2017

Accepted after revision: 02 January 2018

Publication Date:
02 February 2018 (online)


Published as part of the Special Section 9th EuCheMS Organic Division Young Investigator Workshop

Abstract

The influence of high pressure (in the kbar region) on the outcome of the Au(I)-catalyzed cycloisomerization of 1,6- and 1,7-enynes is presented. The positive effect of pressure is particularly marked for reactions involving sterically biased substrates (e.g. 1,6-enynes bearing atert-butyl substituent at the alkyne moiety) and the challenging cyclization of internal 1,7-enynes.

Supporting Information

 
  • References and Notes

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  • 14 General Procedure for the Gold-Catalyzed Cycloisomerization of Nonterminal Enynes; Enyne (0.3 mmol) was weighted in a 3-mL Teflon ampoule. Then, a solution of PPh3AuNTf2 {or [3,5-(t-Bu)2PhO]3PAuNTf2, prepared in situ from gold chloride complex and Ag NTf2} in CH2Cl2 (ca. 2.5 mL) was added. The ampoule was closed with a Teflon screw cap (with a small hole) fitted with a rubber O-ring. Then, the solvent (CH2Cl2) was introduced through a syringe to fill the ampoule completely (no air bubbles left), which was next tightly closed with a screw (bolt) equipped with a rubber O-ring. The ampoule was then placed in a high pressure chamber filled with petroleum ether and compressed to 6 kbar (or to 10 kbar). The procedure is illustrated in the Supporting Information (Figure S2). After 4 h (or 24 h), the system was decompressed, the reaction mixture was transferred to a flask, concentrated and subjected to chromatography (silica gel ca. 10 g, hexane–EtOAc, 95:5).
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  • 17 Mixture 2b/3b (1:7): Prepared in the reaction of 1d following the general procedure with 2 mol% of [3,5-(t-Bu)2PhO]3PAuNTf2 as the catalyst. The mixture of title compounds was isolated in 66% yield as a colorless oil. 1H NMR (400 MHz, CDCl3): δ = 5.14–5.18 (m, 1 H), 3.71 (s, 6 H), 2.94–2.99 (m, 2 H), 2.83 (br s, 2 H), 2.75 (br s, 2 H), 1.65 (s, 3 H), 1.63 (s, 3 H), 1.57 (s, 3 H). Compound 3d: 13C NMR (101 MHz, CDCl3): δ = 172.7, 140.4, 125.7, 124.7, 121.0, 59.2, 52.7, 42.8, 40.5, 35.8, 20.5, 20.3, 18.3. 1H NMR (400 MHz, CDCl3): δ = 6.09 (d, J = 16.1 Hz, 1 H), 5.60 (d, J = 16.0 Hz, 1 H), 5.42–5.46 (m, 1 H), 3.73 (s, 6 H), 3.10 (s, 2 H), 3.07 (s, 2 H), 1.02 (s, 9 H). Compound 2d: 1H NMR (400 MHz, CDCl3): δ = 6.09 (d,J = 16.1 Hz, 1 H), 5.60 (d, J = 16.1 Hz, 1 H), 5.42–5.46 (m, 1 H), 3.73 (s, 6 H), 3.10 (s, 2 H), 3.07 (s, 2 H), 1.02 (s, 9 H). 13C NMR (101 MHz, CDCl3): δ = 172.6, 143.3, 139.7, 124.0, 120.6, 58.6, 52.8, 40.8, 39.9, 33.1, 31.1, 29.5. IR (CH2Cl2): 2954, 2866 (C–H), 1739 (C=O), 1642 (C=C), 1436, 1362, 1256, 1218, 1201 (C–O), 1073, 971 cm–1. HRMS (ESI): m/z [M + Na+] calcd for C15H22O4Na: 289.1416; found: 289.1417.
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  • 25 Compound 7d: Prepared in the reaction of 6d following the general procedure with 0.5 mol% of PPh3AuNTf2 as the catalyst. The title compound was isolated in 61% yield as a colorless oil. 1H NMR (400 MHz, CDCl3): δ = 5.09 (s, 1 H), 3.70 (s, 6 H), 2.65 (d, J = 17.1 Hz, 1 H), 2.34–2.42 (m, 1 H), 2.18–2.29 (m, 2 H), 1.68 (s, 3 H), 164 (s, 3 H), 1.62 (d, J = 1.2 Hz, 3 H), 1.51 (dd, J = 13.0, 10.8 Hz, 1 H), 1.02 (d, J = 6.8 Hz, 3 H). 13C NMR (101 MHz, CDCl3): δ = 172.7, 171.4, 137.1, 130.4, 127.7, 125.9, 54.1 52.5, 52.3, 36.1, 32.9, 27.9, 21.5, 21.2, 19.9, 17.5. IR (CH2Cl2): 2954, 2925 (C–H), 1738 (C=O), 1448, 1435, 1373, 1249, 1200 (C–O), 1084, 1038, 974 cm–1. HRMS (ESI): m/z [M + Na+] calcd for C16H24O4Na: 303.1572; found: 303.1570.
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  • 28 Compound 16a: Prepared in the reaction of 15a following the general procedure (10 kbar) with 2 mol% of PPh3AuNTf2 as the catalyst. The title compound was isolated in 65% yield as a colorless oil. 1H NMR (400 MHz, CDCl3): δ = 5.23–5.27 (m, 1 H), 3.71 (s, 6 H), 2.55–2.62 (m, 2 H), 2.17 (t, J = 6.4 Hz, 2 H), 1.98–2.06 (m, 2 H), 1.62 (s, 6 H), 1.55 (s, 3 H). 13C NMR (101 MHz, CDCl3): δ = 172.2, 140.4, 130.8, 125.4, 119.3, 52.8, 52.5, 30.7, 28.1, 24.7, 21.2, 19.8, 17.9. IR (CH2Cl2): 2952, 2917 (C–H), 1737 (C=O), 1435, 1326, 1253, 1216 (C–O), 1086, 1060 cm–1. HRMS (ESI): m/z [M + Na+] calcd for C15H22O4Na: 289.1416; found: 289.1413.