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Synlett 2009(7): 1175-1179  
DOI: 10.1055/s-0028-1088153
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Hg(OTf)2-Catalyzed Instantaneous Hydration of β- and δ-Hydroxy Internal Alkynes with Complete Regioselectivity

Mugio Nishizawa*, Takayuki Takemoto, Ikuo Sasaki, Mayo Nakano, Elisabeth Ho, Kosuke Namba, Hirofumi Yamamoto, Hiroshi Imagawa
Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan
Fax: +81(88)6553051; e-Mail: mugi@ph.bunri-u.ac.jp;
Further Information

Publication History

Received 13 January 2009
Publication Date:
20 March 2009 (online)

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Abstract

The hydration of β- and δ-hydroxy internal alkynes catalyzed by Hg(OTf)2 took place instantaneously to give ketones with complete regioselectivity under mild conditions, whereas the hydration of internal alkyne without hydroxy moiety was very slow and gave a mixture of ketones. If the hydroxy group is located more than five carbons from the triple bond it has no significant effect upon the hydration reaction.

Key words

Hg(OTf)2 - homogeneous catalysis - hydroxy internal alkyne - regioselectivity - neighboring-group effects

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Present address: Division of Chemistry, Graduate School of Science, Hokkaido University, Kita-ku, Saporo 060-0810, Japan.

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Typical Experimental Procedure
To a stirred mixture of dec-5-yn-1-ol (3, 280 mg, 2 mmol) and H2O (108 mg, 6 mmol) in MeCN (6.6 mL) was added a solution of Hg(OTf)2 (0.1 M MeCN soln, 0.2 mL, 0.02 mmol) at r.t., and the mixture was stirred for 5 min at the same temperature. After addition of Et3N (30 µL) and then brine (6 mL), the organic materials were extracted with Et2O. Dried and concentrated extract was subjected to a column chromatography on SiO2 using hexane and EtOAc (2:1) as an eluent to give 1-hydroxydecan-5-one (4, 275 mg, 90% yield) as a colorless oil.²0a

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All new compounds were fully characterized by spectroscopic methods.