Formamides

About: Formamides is a research topic. Over the lifetime, 842 publications have been published within this topic receiving 12785 citations.

A Well‐Defined Iron Catalyst for the Reduction of Bicarbonates and Carbon Dioxide to Formates, Alkyl Formates, and Formamides

Abstract: Keywords: carbon dioxide ; formate ; homogeneous catalysis ; hydrogenation ; iron ; Formic-Acid ; Homogeneous Hydrogenation ; Aqueous-Solution ; Metal-Complexes ; Dihydrogen ; Efficient ; Ketones ; Co2 ; Hydrosilylation ; Conversion Reference EPFL-ARTICLE-172116doi:10.1002/anie.201004263View record in Web of Science Record created on 2011-12-16, modified on 2017-05-12

Silver-Mediated Direct Amination of Benzoxazoles: Tuning the Amino Group Source from Formamides to Parent Amines

Abstract: The construction of C N bonds of heteroaromatic compounds is a highly important transformation in synthetic chemistry since it can offer nitrogen-containing molecules of great interest in biological, pharmaceutical, and materials sciences. During the past decades, remarkable progresses have been made in the metal-facilitated C N bond-forming reactions such as hydroamination or oxidative amidation of double or triple bonds as well as the Buchwald–Hartwigtype cross couplings. Despite these significant advances, direct installation of amino groups or their surrogates on aryl or alkyl C H bonds is still challenging. To meet this demand, a new approach involving oxidative addition of amino or amido moieties into hydrocarbons has been extensively studied. 6] In particular, site-selective amination of preorganized arenes through catalytic C H bond activation was recently developed. An ortho-selective amination of naphthols through thermal cleavage of disubstituted hydrazines was also reported. Most recently, Mori and co-workers have reported an oxidative amination of azoles using copper salts at high temperature ( 140 8C). Herein, we describe an unprecedented silver-mediated C N bond formation of benzoxazoles by decarbonylative coupling with formamides. On the basis of mechanistic considerations, we have also developed a direct amination protocol with parent amines under very mild reaction conditions. In line with our recent efforts on metal-catalyzed C H bond functionalization, we wondered whether subjection of electron-rich heteroarenes to Pd/Ag-catalytic systems in the presence of formamides could provide amidated products (Scheme 1). To our surprise, when benzoxazole (1a) was treated with N,N-dimethylformamide (DMF) using the Pd(OAc)2/Ag2CO3 system in the presence of an acetic acid additive, 2-aminated benzoxazole 2a was obtained as a single product, albeit in moderate yield. In contrast, no amidated product 3a was observed under other reaction conditions examined. Subsequent studies revealed that the unexpected decarbonylative amination reaction also proceeded even in the absence of the palladium catalyst and with slightly higher yields. Encouraged by these preliminary result, we subsequently tried to optimize the decarbonylative amination conditions using benzoxazole (1a) in neat DMF (40 equiv), as shown in Table 1. Although no desired product was obtained in the absence of the silver salt or the acid additives (entries 1 and 2), addition of certain types of carboxylic acids promoted the transformation in the presence of silver salts (entries 3–8). Among various acids examined, p-anisic acid turned out to be most effective for the amination reaction (entry 8). Catalytic amounts of Ag2CO3 did not furnish the desired product (entry 9), thus indicating that the use of stoichiometric amounts of silver salts is essential for smooth conversion under these reaction conditions. In addition, other silver sources such as Ag2O, AgOAc, AgOTf (Tf = triflate), or AgF (entry 10) were less effective when compared to Ag2CO3. [13] Scheme 1. Decarbonylative amination of benzoxazole (1a).

ZnO as a new catalyst for N-formylation of amines under solvent-free conditions.

Abstract: The treatment of amines with formic acid in the presence of ZnO under solvent-free conditions brings about highly and efficient N-formylation to give the corresponding formamides in excellent yields. The N-formylation reaction not only involves mild conditions, simple operation, and high yields but also high chemoselectivity.

Highly Efficient Ruthenium-Catalyzed N-Formylation of Amines with H₂ and CO₂.

Abstract: A highly efficient catalyst system based on ruthenium-pincer-type complexes has been discovered for N-formylation of various amines with CO2 and H2, thus affording the corresponding formamides with excellent productivity (turnover numbers of up to 1,940,000 in a single batch) and selectivity. Using a simple catalyst recycling protocol, the catalyst was reused for 12 runs in N,N-dimethylformamide production without significant loss of activity, thus demonstrating the potential for practical utilization of this cost-effective process. A one-pot two-step procedure for hydrogenation of CO2 to methanol via the intermediacy of formamide formation has also been developed.

Betaine Catalysis for Hierarchical Reduction of CO2 with Amines and Hydrosilane To Form Formamides, Aminals, and Methylamines

Abstract: An efficient, sustainable organocatalyst e.g. glycine betaine was developed for reductive functionalization of CO2 with amines and diphenylsilane. Methylamines and formamides could respectively be obtained with high yield via tuning CO2 pressure and reaction temperature. Betaine catalysis was efficient for the formation of formamide at 10 bar CO2, 50 oC. Exclusively yielding methylamines from various amines with atmospheric pressure of CO2 was attained at 70 oC. Based on identification of the key intermediate i.e. aminal, an alternative mechanism for methylation involving the C0 silyl acetal and aminal was proposed. Furthermore, reducing CO2 amount to approx. 1 equiv. afforded aminal with high yield and selectivity. Therefore, betaine catalysis in this study afforded the products with diversified energy content i.e. formamide, aminal and methylamine respectively through hierarchical 2-, 4- and 6-electron reduction of CO2 coupled with C-N bond formation for the first time.