Synlett 2014; 25(14): 2067-2071
DOI: 10.1055/s-0034-1378333
letter
© Georg Thieme Verlag Stuttgart · New York

Lithium(1+)-Catalyzed Nazarov-Type Cyclization of 1-Arylbuta-2,3-dien-1-ols: Synthesis of Benzofulvene Derivatives

Masahiro Sai
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan   Fax: +85(75)3832438   Email: matsubara.seijiro.2e@kyoto-u.ac.jp
,
Seijiro Matsubara*
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan   Fax: +85(75)3832438   Email: matsubara.seijiro.2e@kyoto-u.ac.jp
› Author Affiliations
Further Information

Publication History

Received: 02 May 2014

Accepted after revision: 25 May 2014

Publication Date:
09 July 2014 (online)


Abstract

Lithium hexafluorophosphate proved to be an effective catalyst for a Nazarov-type cyclization of 1-arylbuta-2,3-dien-1-ols to afford benzofulvenes, valuable as building blocks for functional materials and bioactive compounds.

Supporting Information

 
  • References and Notes

  • 5 Toda F, Ooi N, Akagi K. Bull. Chem. Soc. Jpn. 1971; 44: 1050
  • 7 Cordier P, Aubert C, Malacria M, Lacôte E, Gandon V. Angew. Chem. Int. Ed. 2009; 48: 8757
  • 8 Poonoth M, Krause N. Adv. Synth. Catal. 2009; 351: 117 ; and references cited therein
  • 9 Activation of the alcohol functionality by a combination of LiNTf2 and Bu4NPF6 has been reported, see: Niggemann M, Meel MJ. Angew. Chem. Int. Ed. 2010; 49: 3684
  • 10 α-Allenols can be readily prepared by titanium-mediated selective allenylation of ketones and aldehydes, see: Nakagawa T, Kasatkin A, Sato F. Tetrahedron Lett. 1995; 36: 3207
  • 11 Benzofulvenes 2 readily undergo polymerization even at low temperature (–20 °C) when they are stored as neat oils.
  • 12 LiPF6 (H2O: 20 ppm max; 99.9+%-Li) was purchased from Strem Chemicals, Inc., Newburyport, MA, USA.
  • 13 A combination of LiPF6 with hexane has been reported to be an efficient system for the tetrahydropyranylation of tertiary alcohols, see: Hamada N, Sato T. Synlett 2004; 1802
  • 14 The spectroscopic data for E-3 were in full agreement with those reported in the literature.
  • 16 2,3-Dimethyl-1-methylene-1H-indene (2a); Typical Procedure In a glove box, an oven-dried test tube equipped with a magnetic stirrer bar was charged with LiPF6 (3.8 mg, 0.025 mmol). The tube was removed from the glove box and a solution of α-allenol 1a (87.1 mg, 0.50 mmol) in hexane (3.0 mL) was added. The mixture was heated at 65 °C for 1 h, cooled to r.t., and passed through a short column of activated alumina, eluting with Et2O. The eluent was concentrated and the residue was purified by column chromatography (silica gel, hexane) to give a yellow oil; yield: 67.7 mg (87%). IR (neat): 3047, 2971, 1611, 1441, 1412 cm–1; 1H NMR (500 MHz, CDCl3): δ = 2.05–2.07 (m, 3 H), 2.08–2.10 (m, 3 H), 5.57 (s, 1 H), 5.89 (s, 1 H), 7.10–7.14 (m, 2 H), 7.23 (ddd, J = 7.5, 7.5, 1.0 Hz, 1 H), 7.48–7.52 (m, 1 H); 13C NMR (125 MHz, CDCl3) δ = 9.8, 10.7, 108.4, 117.7, 119.0, 124.8, 128.1, 132.0, 136.2, 137.3, 144.7, 148.7; HRMS (EI): m/z [M+] calcd for C12H12: 156.0939; found: 156.0933.