Amide Synthesis from Esters with Nitriles under Solvent-free Conditions Using Molecular Iodine as a Catalyst

Abstract

and ZnCl 2 /SiO 2 12). These are strong acids or heavy metal compounds, which are very expensive and/or toxic. In addition, solvent-free reactions are important in green chemistry. Accordingly, we investigated the amidation of esters Abstract: The reaction of esters with nitriles, using iodine as a catalyst under solvent-free conditions, was investigated. For example, 1-phenylethyl acetate reacted with benzonitrile in the presence of iodine to afford the amide, N-(1-phenylethyl)benzamide. Addition of water was effective in promoting amidation. The most suitable conditions were investigated, and determined as follows: temperature = 80℃, molar ratio of nitrile:alcohol:iodine:water = 1:3:0.2:1.0, and reaction time = 18 h. The amidation reactivity depended on the stability of the cationic intermediate formed from the ester. Only the reaction of 2-phenylpropan-2-yl acetate with benzonitrile gave no amide compound; rather, the cyclic compound, 1,1,3-trimethyl-3-phenyl-2,3-dihydro-1H-indene was obtained in 90% yield. The reaction of (-)-bornyl acetate with benzonitrile produced the racemic amide compound, (±)-exo-N-isobornylbenzamide, in 82% yield.

Crystal structures of two (±)-exo-N-isobornylacetamides

“…When the optically active (À)-borneol was submitted to standard Ritter reaction conditions, the expected compounds were isolated in acceptable yields albeit in the racemic form. A similar type of racemization due to a 6,2hydride shift was described in the Ritter reaction of (À)bornyl acetate (Hanzawa et al, 2012.). Previously, compounds (AE)-(1) and (AE)-(2) have been obtained as side products in a ISSN 2056-9890 cationic rearrangement of (À)--pinene in the presence of the corresponding nitriles (Ung et al, 2014).…”

Zn(ClO4)2⋅6H2O‐Catalyzed One‐Pot Synthesis of Amides via Ritter Reaction with Alcohols, Acetic Anhydride and Nitriles

“…Subsequently, a series of novel catalysts including homogeneous and heterogeneous catalysts were developed for replacing the employment of acids . On the other hand, some alternative starting substrates such as acetic esters, halohydrocarbons and ethers were also explored to react with nitriles to form amides. Among these novel starting materials, acetic esters were ease to be obtained compared with ethers and halohydrocarbons.…”

Iodine mediated one-pot synthesis of 3-cyano and 3-cyano-4-methylcoumarins

“…The former reaction between 2-hydroxybenzaldehyde and malononitrile gives 2-imino-2Hchromene-3-carbonitrile as an intermediate that has to be hydrolysed under acidic conditions. [20][21][22][23] Thus, it was thought worthwhile to study the reaction of 2-hydroxybenzaldehydes and malononitrile using iodine as catalyst, which led to the synthesis of 3-cyanocoumarins in a single step. 19 In recent years, molecular iodine was used as a mild and efficient condensing agent in various organic reactions.…”