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All posts   Subject: Pd-catalyzed synth of aldehydes from aryl iodides   Please login to post  

 
    Lego
(Hive Bee)
11-11-04 21:04
No 541078
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      Pd-catalyzed synth of aldehydes from aryl iodides
(Rated as: excellent)
    

Palladium-Catalyzed Synthesis of Aldehydes from Aryl Iodides and Acetic Formic Anhydride
Sandro Cacchi, Giancarlo Fabrizi, and Antonella Goggiamani
J. Comb. Chem., 2004, 6(5), 692-694
DOI:10.1021/cc049906h




entry aryl iodide 1 procedure yield % of 2b  
1 p-MeO-C6H4-I A 72 2a
2 m-MeO-C6H4-I A 60 2b
3 p-Me-C6H4-I A 82 2c
4 o-Me-C6H4-I A 50 2d
5 p-MeCONH-C6H4-I Ac 75 2e
6 p-MeCONH-C6H4-I Ac,d 51 2e
7 p-EtOOC-C6H4-I Be 71 2f
8 p-EtOOC-C6H4-I Bf,g 57 2f
9 p-HOOC-C6H4-I B 76 2g
10 m-HOOC-C6H4-I B 66 2h
11 p-MeCO-C6H4-I B 83 2i
12 2-Me-5-NO2-C6H3-I B 62 2j
13 4-Me-3-NO2-C6H3-I B 62 2k
14 p-NO2-C6H4-I B 25 2l


a Unless otherwise stated, reactions were carried out at 60 °C for 48 h on a 0.855-mmol scale in 3 mL of anhydrous solvent using, procedure A, 1 equiv of aryl iodide, 2 equiv of acetic formic anhydride, 0.025 equiv of Pd2(dba)3, 0.05 equiv of dppe, 1.5 equiv of Et3SiH, and 2 equiv of EtN(Pr-i)2 in 3 mL of MeCN; procedure B, 1 equiv of aryl iodide, 2 equiv of acetic formic anhydride, 0.025 equiv of Pd2(dba)3, 0.05 equiv of dppe, 1.5 equiv of Et3SiH, 2 equiv of EtN(Pr-i)2, 3 equiv of LiCl in 3 mL of DMF.
b All products gave appropriate 1H and 13C NMR and IR spectra.
c 65 h.
d In DMF.
e 2f was isolated in 62% yield when the reaction was carried out with 4 equiv of anhydride at 80 °C for 30 h.
f In MeCN, using 0.05 equiv of Pd/C 5%. Ethyl benzoate, derived from the reduction of the corresponding arylpalladium oxidative addition complex, was isolated in 22% yield. When the same reaction was run omitting LiCl, the aldehyde product was isolated in 18% yield.
g 4 days.



Therefore, we decided to investigate the utilization of preformed acetic formic anhydride, which can be readily prepared from acetyl chloride and sodium formate.12

12 Krimen, L. I., Org. Synth., 1970, 50, 1 (http://www.orgsyn.org/orgsyn/prep.asp?prep=cv6p0008)




Please note that this approach is only for people with too much money as triethylsilane (Et3SiH) and Pd2(dba)3 are quite expensive. For alternatives to synthesize benzaldehydes from aryl halogenides see for example:
Post 473103 (Rhodium: "Phenyl-MgBr + Orthoformate -> Benzaldehyde", Methods Discourse)
Post 377691 (moo: "Aldehydes from Grignard reagents with formic acid", Methods Discourse)
Post 365801 (Rhodium: "Strangest benzaldehyde synth this far", Novel Discourse)

The tendency is to push it as far as you can
 
 

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