Synlett 2003(10): 1469-1473
DOI: 10.1055/s-2003-40857
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Facile Double Nucleophilic Addition of Thiols and Tetraallyltin to Latent 2-Alkynals Using in situ Hydrolysis of the Imino Functionality Promoted by Tin(IV) Chloride Pentahydrate

Makoto Shimizu*, Takafumi Nishi, Akihiro Yamamoto
Department of Chemistry for Materials, Mie University, Tsu, Mie 514-8507, Japan
Fax: +81(59)2319413; e-Mail: mshimizu@chem.mie-u.ac.jp;
Further Information

Publication History

Received 2 May 2003
Publication Date:
24 July 2003 (online)

Abstract

In the presence of SnCl4˙5H2O, a mixture of thiols and tetraallyltin underwent 1,4- and 1,2-addition, respectively, with the imines derived from 3-alkynals to give (Z)-1-sulfenyl-1,5-alkadien-3-ols in good yields, where the hydrolysis of the intermediary imino species was found to be crucial.

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A Typical Procedure for the Addition Reaction: To a suspension of SnCl4˙5H2O (31.2 mg, 0.06 mmol) in PhCH3 (1.5 mL) was added a solution of N-(1-phenethyl)phenyl-propargylidenamine (46.7 mg, 0.2 mmol) in CH2Cl2 (1.5 mL) at -85 °C, and the mixture was stirred at -85 °C for
5 min. A solution of benzyl mercaptan (37.3 mg, 0.3 mmol) in PhCH3 (1.5 mL) was added to the resulting mixture at
-85 °C, and the mixture was stirred at -85 °C for 10 min. A solution of tetraallyltin (28.3 mg, 0.1 mmol) in PhCH3 (1.5 mL) was added to the resulting mixture at -85 °C and the mixture was gradually warmed to r.t. during 17 h. Sat. aq NaHCO3 was added to the mixture which was extracted with EtOAc. The combined extracts were dried (Na2SO4) and concentrated in vacuo to give a crude oil. Purification on silica gel TLC (n-hexane:EtOAc = 4:1 as an eluent) gave (Z)-1-benzylthio-1-phenylhexa-1,5-dien-3-ol (47.6 mg, 84%) as a colorless oil.

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When TiCl4 or SnCl4 was used as a Lewis acid, only 1,4-addition of thiol was observed.

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The olefin geometry was determined using the NOESY experiment.