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Synlett 2006(13): 2071-2074  
DOI: 10.1055/s-2006-948198
LETTER
© Georg Thieme Verlag Stuttgart · New York

Dibutyltin Oxide Catalyzed Allyl-Transfer Reaction from Tertiary ­Homoallylic Alcohols to Aldehydes

Akira Yanagisawa*a, Takahiro Aokib, Takayoshi Araia
a Department of Chemistry, Faculty of Science, Chiba University, Inage, Chiba 263-8522, Japan
b Graduate School of Science and Technology, Chiba University, Inage, Chiba 263-8522, Japan
Fax: +81(43)2902789; e-Mail: ayanagi@scichem.s.chiba-u.ac.jp;
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Publication History

Received 22 May 2006
Publication Date:
09 August 2006 (online)

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Abstract

A catalytic allyl-transfer reaction from tertiary homo­allylic alcohols to aldehydes was achieved using dibutyltin oxide as a catalyst in toluene under reflux conditions. Various secondary ­homoallylic alcohols were prepared in high yield (up to 99%). When β-alkylated tertiary homoallylic alcohols were used, branched products were exclusively obtained.

Key words

aldehydes - allylations - organometallic reagents - regio­selectivity - tin

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Typical experimental procedure for crotyl-transfer reaction to aldehydes catalyzed by dibutyltin oxide (Table [2] , Entry 4). Under an argon atmosphere, 4-methoxybenzaldehyde (68.1 mg, 0.50 mmol) was added to a solution of dibutyltin oxide (12.4 mg, 0.05 mmol) and crotyl donor (238 mg, 1.00 mmol) in dry toluene (2 mL) at r.t. After stirring for 30 min the mixture was heated at reflux (oil bath temperature: 125-130 °C) for 24 h and then treated with MeOH (2 mL), brine (2 mL), and solid KF (ca. 2 g) at r.t. for 2 h. The resulting precipitate was filtered off and the filtrate diluted with H2O (30 mL) and extracted with Et2O (3 ¥ 30 mL). The combined organic extracts were washed with brine (20 mL), dried over anhydrous Na2SO4, and concentrated in vacuo after filtration. The residual crude product was purified by column chromatography on silica gel to give a syn/anti mixture of the corresponding homoallylic alcohol (96.0 mg, >99% yield). The syn/anti ratio was determined to be 73:27 by 1H NMR analysis. Spectral data of a 73:27 mixture of the syn and anti isomers: TLC R f = 0.17 (hexane-EtOAc, 7:1); 1H NMR (400 MHz, CDCl3): δ = 0.82 (d, J = 7.0 Hz, 0.81 H), 0.99 (d, J = 6.8 Hz, 2.19 H), 2.31 (br s, 1 H), 2.42 (m, 0.27 H), 2.51 (m, 0.73 H), 3.76 (s, 3 H), 4.26 (d, J = 8.0 Hz, 0.27 H), 4.46 (d, J = 5.8 Hz, 0.73 H), 4.97-5.01 (m, 1.46 H), 5.12-5.18 (m, 0.54 H), 5.64-5.74 (m, 0.73 H), 5.74-5.85 (m, 0.27 H), 6.83 (d, J = 8.7 Hz, 1.46 H), 6.85 (d, J = 8.5 Hz, 0.54 H), 7.17 (d, J = 8.7 Hz, 1.46 H), 7.21 (d, J = 8.5 Hz, 0.54 H); 13C NMR (100 MHz, CDCl3): δ = 14.4, 16.4, 44.5, 46.1, 55.0, 55.0, 76.9, 77.3, 113.2, 113.4, 115.1, 116.3, 127.6, 127.8, 134.5, 134.7, 140.2, 140.8, 158.6, 158.9. Spectral data (1H and 13C NMR) of the mixture of the syn and anti isomers indicated good agreement with reported data. [10]