Oxidative Decarboxylation of 2-Aryl Carboxylic Acids Using (Diacetoxyiodo)benzene for Preparation of Aryl Aldehydes, Ketones, and Nitriles

Abstract

A novel synthetic application of the hypervalent iodine reagent, (diacetoxyiodo)benzene, and catalytic amount of sodium azide in acetonitrile for oxidative decarboxylation of 2-aryl carboxylic acids into corresponding aldehydes, ketones, and nitriles at room temperature is described. The advantages of this protocol are shorter reaction times and mild reaction conditions to obtain moderate to good yields

Key words

(diacetoxyiodo)benzene - decarboxylation - aldehydes - ketones - nitriles

References and Notes

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17

Representative Procedure for Decarboxylation of Phenylacetic Acid (Table 1, Entry 1)
(Diacetoxyiodo)benzene (1.5 equiv) and NaN₃ (0.12 equiv) in MeCN (10 mL) were stirred at 0 ˚C for 2 min, then phenyl acetic acid (1 equiv) was added to the stirred solution. The reaction mixture was allowed to come at r.t. and stirring continued until completion of reaction (TLC), when it was quenched with H₂O (25 mL) and extracted with CHCl₃ (3 × 10 mL). The combined organic layers were washed with dilute NaHCO₃ (20 mL), followed by H₂O (3 × 20 mL), dried over Na₂SO₄, and concentrated in vacuo. The residue was purified by column chromatography on silica gel (hexane-EtOAc = 9:1) to yield benzaldehyde (88%) as a colorless liquid.

18

Representative Procedure for Decarboxylation of α-Amino(phenyl)acetic Acid (Table 1, Entry 13)
(Diacetoxyiodo)benzene (1.5 equiv) and NaN₃ (0.12 equiv) in MeCN (10 mL) were stirred at r.t. for 2 min, then α-amino-(phenyl)acetic acid (1 equiv) was added to the stirred solution. Stirring was continued until completion of reaction (TLC), when it was quenched with H₂O (25 mL) and worked up as mentioned above to yield benzonitrile (90%) as a colorless liquid; bp 188 ˚C. IR (neat): 2230, 2256, 2178, 1682, 1572, 1492 cm^-¹. ^¹³C NMR (75 MHz, CDCl₃): δ = 132.84, 132.10, 129.21, 118.82, 112.41.