Iridium-Catalyzed Carbonyl Allylations by Allylic Alcohols with Tin(II) Chloride

Abstract

Iridium complex [IrCl(cod)]₂ can function as a catalyst for the allylation of aldehydes and ketones by allylic alcohols upon addition of an equimolar amount of SnCl₂ in THF-H₂O; the reaction is carried out between room temperature and 50 °C to give the corresponding homoallylic alcohols.

nucleophilic addition - carbonyl allylation - π-allyliridium - tin(II) chloride - allylic alcohols

References

1 Masuyama Y. Kaneko Y. Kurusu Y. Tetrahedron Lett.  2004,  45:  8969 

For reviews containing carbonyl allylations by allylic alcohols via umpolung of π-allylpalladium, see:

2a Masuyama Y. J. Synth. Org. Chem., Jpn.  1992,  50:  202 

2b Masuyama Y. In Advances in Metal-Organic Chemistry   Vol. 3:  Liebeskind LS. JAI Press; Greenwich CT: 1994.  p.255-303  

2c Tamaru Y. In Perspectives in Organopalladium Chemistry for the XXI Century   Tsuji J. Elsevier Science; Switzerland: 1999.  p.215-231  

2d Tamaru Y. In Handbook of Organopalladium Chemistry for Organic Synthesis   Negishi E. Wiley; New York: 2002.  p.1917-1953  

3 For the palladium-catalyzed carbonyl allylation by allylic alcohols with SnCl₂, see: Takahara JP. Masuyama Y. Kurusu Y. J. Am. Chem. Soc.  1992,  114:  2577 

Palladium-catalyzed carbonyl allylations need over two equivalents of reducing agent for one equivalent of allylic alcohol and/or aldehyde:

4a For triethylborane, see: Kimura M. Tomizawa T. Horino Y. Tanaka S. Tamaru Y. Tetrahedron Lett.  2000,  41:  3627 

4b For indium iodide, see: Araki S. Kamei T. Hirashita T. Yamamura H. Kawai M. Org. Lett.  2000,  2:  847 

4c For diethylzinc, see: Kimura M. Shimizu M. Tanaka S. Tamaru Y. Tetrahedron  2005,  61:  3709 

5 For nickel-catalyzed carbonyl allylation with over two equivalents of indium iodide and one equivalent of aldehyde, see: Hirashita T. Kambe S. Tsuji H. Omori H. Araki S. J. Org. Chem.  2004,  69:  5054 

6 Takeuchi R. Synlett  2002,  1954 ; and references cited therein

7

A typical procedure is as follows: To a solution of 1 (0.087 g, 1.5 mmol), benzaldehyde (0.11 g, 1.0 mmol), and SnCl₂ (0.28 g, 1.5 mmol) in THF (2 mL) and H₂O (0.1 mL) was added [IrCl(cod)]₂ (0.013 g, 0.02 mmol), and the solution was stirred at r.t. for 20 h. The solution was diluted with Et₂O-CH₂Cl₂ (2:1; 120 mL), washed with aq 10% HCl solution (20 mL), aq NaHCO₃ solution (20 mL), H₂O (20 mL), and brine (20 mL). The extracts were dried over anhyd MgSO₄. After evaporation of the solvent, column chromatography (silica gel; hexane-EtOAc, 7:1), and then HPLC (Japan Analytical Industry Co. Ltd., LC-908, JAIGEL-2H; CHCl₃) afforded 0.13 g (87%) of 1-phenyl-3-buten-1-ol as a colorless oil.

The structures and/or ratios were confirmed by comparison of the IR and ¹H NMR spectra with those of authentic samples, see:

8a

ref. 3

8b Ito A. Kishida M. Kurusu Y. Masuyama Y. J. Org. Chem.  2000,  65:  494 

Since the reactivity of cyclohexanecarboxaldehyde is low, initially produced 5b may react with excess cyclohexanecarboxaldehyde and isomerize to sterically unhindered and thermodynamically stable 5a via a homoallyloxycarbenium ion intermediate:

9a Nokami J. Ohga M. Nakamoto H. Matsubara T. Hussain I. Kataoka K. J. Am. Chem. Soc.  2001,  123:  9168 

9b

Ref. 1.

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¹H NMR (500 MHz): δ = 3.93 (d, J = 6 Hz, 2 H), 5.09 (d, J = 10 Hz, 1 H), 5.23 (d, J = 17 Hz, 1 H), 5.83-5.91 (m, 1 H); ¹³C NMR (125 MHz): δ = 71.5, 116.0, 136.1.