1864-97-7Relevant academic research and scientific papers
The formyloxyl radical: Electrophilicity, C-H bond activation and anti-Markovnikov selectivity in the oxidation of aliphatic alkenes
Iron, Mark A.,Khenkin, Alexander M.,Neumann, Ronny,Somekh, Miriam
, p. 11584 - 11591 (2020/11/23)
In the past the formyloxyl radical, HC(O)O, had only been rarely experimentally observed, and those studies were theoretical-spectroscopic in the context of electronic structure. The absence of a convenient method for the preparation of the formyloxyl radical has precluded investigations into its reactivity towards organic substrates. Very recently, we discovered that HC(O)O is formed in the anodic electrochemical oxidation of formic acid/lithium formate. Using a [CoIIIW12O40]5- polyanion catalyst, this led to the formation of phenyl formate from benzene. Here, we present our studies into the reactivity of electrochemically in situ generated HC(O)O with organic substrates. Reactions with benzene and a selection of substituted derivatives showed that HC(O)O is mildly electrophilic according to both experimentally and computationally derived Hammett linear free energy relationships. The reactions of HC(O)O with terminal alkenes significantly favor anti-Markovnikov oxidations yielding the corresponding aldehyde as the major product as well as further oxidation products. Analysis of plausible reaction pathways using 1-hexene as a representative substrate favored the likelihood of hydrogen abstraction from the allylic C-H bond forming a hexallyl radical followed by strongly preferred further attack of a second HC(O)O radical at the C1 position. Further oxidation products are surmised to be mostly a result of two consecutive addition reactions of HC(O)O to the CC double bond. An outer-sphere electron transfer between the formyloxyl radical donor and the [CoIIIW12O40]5- polyanion acceptor forming a donor-acceptor [D+-A-] complex is proposed to induce the observed anti-Markovnikov selectivity. Finally, the overall reactivity of HC(O)O towards hydrogen abstraction was evaluated using additional substrates. Alkanes were only slightly reactive, while the reactions of alkylarenes showed that aromatic substitution on the ring competes with C-H bond activation at the benzylic position. C-H bonds with bond dissociation energies (BDE) ≤ 85 kcal mol-1 are easily attacked by HC(O)O and reactivity appears to be significant for C-H bonds with a BDE of up to 90 kcal mol-1. In summary, this research identifies the reactivity of HC(O)O towards radical electrophilic substitution of arenes, anti-Markovnikov type oxidation of terminal alkenes, and indirectly defines the activity of HC(O)O towards C-H bond activation.
Mechanistic Insight into Weak Base-Catalyzed Generation of Carbon Monoxide from Phenyl Formate and Its Application to Catalytic Carbonylation at Room Temperature without Use of External Carbon Monoxide Gas
Konishi, Hideyuki,Matsubara, Mika,Mori, Keisuke,Tokiwa, Takaki,Arulmozhiraja, Sundaram,Yamamoto, Yuta,Ishikawa, Yoshinobu,Hashimoto, Hiroshi,Shigeta, Yasuteru,Tokiwa, Hiroaki,Manabe, Kei
supporting information, p. 3592 - 3601 (2017/10/24)
The mechanisms of the weak base-catalyzed generation of carbon monoxide (CO) and phenol from phenyl formate were investigated by experimental and theoretical methods. Kinetic studies revealed a first-order reaction in both phenyl formate and the base. The reaction was found to proceed by an E2 α-elimination pathway, which involves the abstraction of the formyl proton of phenyl formate, simultaneously generating CO and phenoxide. The reaction rate was affected by the substituents on phenyl formate, the polarity of solvents, and the basicity of bases. The mechanistic insight obtained from these studies permitted the chemical control of the rate of CO generation, which was the key to the development of the external CO-free Pd-catalyzed phenoxycarbonylation of haloarenes at room temperature. Because of the mild reaction conditions and wide substrate scope, this phenoxycarbonylation constitutes a general, safe, and practical method to synthesize arenecarboxylic acid esters. (Figure presented.).
Solvent- and catalyst-free N-formylations of amines at ambient condition: Exploring the usability of aromatic formates as N-formylating agents
Batuta, Shaikh,Begum, Naznin Ara
, p. 137 - 147 (2017/01/11)
A solvent- and catalyst-free N-formylation protocol has been developed for amines (1s–21s) where aromatic formates (1r–6r) were used as the N-formylating agents. The amine substrates include both primary and secondary aromatic amines (1s–19s) as well as aliphatic amine (20s) and a primary amide (21s). Structures of both the aromatic formate and amine components strongly influenced the rate of the reaction and yield of the N-formamide products. The reaction condition is mild and easy to operate. This protocol can be done smoothly under ambient conditions and gives high yield of formamide products. Furthermore, the present method cannot be applied for the formylation of thiol group (22s). This signifies its possible use for the chemoselective N-formylation of amine in the presence of thiol functionality.
Palladium-Catalyzed Carbonylative Synthesis of Aryl Formates under Mild Conditions
Jiang, Li-Bing,Li, Rui,Li, Hao-Peng,Qi, Xinxin,Wu, Xiao-Feng
, p. 1788 - 1791 (2016/06/01)
Aryl formates have been extensively applied as CO sources in CO-free carbonylation reactions. However, there are no catalytic synthetic procedures for their preparation. In this manuscript, we developed a convenient palladium-catalyzed procedure for the synthesis of aryl formates. Good yields were achieved under mild reaction conditions with formic acid as the formyl source. A formyl meeting: A convenient palladium-catalyzed carbonylation procedure for the synthesis of aryl formates is developed. Good yields are achieved under mild reaction conditions with formic acid as the formyl source.
Understanding the efficacy of N,N-dimethylformamide and oxalyl chloride combination as chemoselective O-formylating agent: An unified experimental and theoretical study
Batuta, Shaikh,Ali, Md. Ashif,Chatterjee, Anirban,Alam, Md. Niharul,Das, Sreeparna,Mandal, Debabrata,Begum, Naznin Ara
supporting information, p. 692 - 700 (2016/06/08)
We have developed a simple but efficient synthetic protocol for the O-formylation of a wide range of aromatic hydroxyl/phenolic substrates using an N,N-dimethylformamide (DMF) and oxalyl chloride [(COCl)2] combination in dichloromethane (DCM) as solvent at ambient temperature. The DMF/(COCl)2combination was found to be highly chemoselective for the aromatic/phenolic hydroxyl group over aliphatic hydroxyl or aromatic amine/thiol groups. This chemoselectivity of DMF/(COCl)2combination towards O-formylation of aromatic alcohols was explained on the basis of outcomes of both experimental and density functional theory–based theoretical studies.
Three step procedure for the preparation of aromatic and aliphatic difluoromethyl ethers from phenols and alcohols using a chlorine/fluorine exchange methodology
Dolbier Jr., William R.,Wang, Fei,Tang, Xiaojun,Thomoson, Charles S.,Wang, Linhua
, p. 72 - 76 (2014/03/21)
Difluoromethyl ethers are prepared from phenols in three steps via their respective formate ester derivatives. The formates are first converted to dichloromethyl ethers by treatment with PCl5. These ethers are then induced to undergo chlorine/fluorine exchange to form the respective difluoromethyl ethers. The chlorine/fluorine exchange is carried out by either a room temperature, solvolytic process using THF-5HF or Et3N-3HF as exchange medium, where HF is the ultimate source of fluorine, or by a direct displacement process in sulfolane at 125 C, where KF is the source of fluorine. By one or another of these processes, virtually all phenols, electron-rich and electron-poor, can be converted to their respective difluoromethyl ethers in good yields. Aliphatic alcohols are also able to be converted to their difluoromethyl ether derivatives using the Et3N-3HF exchange medium.
Palladacycle-catalyzed carbonylation of aryl iodides or bromides with aryl formates
Chen, Guangwei,Leng, Yuting,Yang, Fan,Wang, Shiwei,Wu, Yangjie
, p. 1488 - 1494 (2014/01/06)
An efficient palladacycle-catalyzed aromatic carbonylation reaction of aryl formates with aryl iodides or bromides has been developed. Commercially available and easily prepared aryl formates were employed as carbonyl sources without the use of external carbon monoxide. The present catalytic system shows broad functional group tolerance and affords aryl benzoate derivatives in good to excellent yields. Copyright
Palladium-catalyzed esterification of aryl halides using aryl formates without the use of external carbon monoxide
Fujihara, Tetsuaki,Hosoki, Tomoya,Katafuchi, Yuko,Iwai, Tomohiro,Terao, Jun,Tsuji, Yasushi
experimental part, p. 8012 - 8014 (2012/09/08)
Aryl formates are efficient carbon monoxide sources in palladium-catalyzed esterification of aryl halides. The carbonylation readily proceeds at ambient pressure without the use of external carbon monoxide to afford the corresponding esters in high yields.
O-acylation of substituted phenols with various alkanoyl chlorides under phase-transfer catalyst conditions
Simion, Alina Marieta,Hashimoto, Iwao,Mitoma, Yoshiharu,Egashira, Naoyoshi,Simion, Cristian
scheme or table, p. 921 - 931 (2012/02/01)
Esterification of several types of mono-and disubstituted phenols with various mono-and dialkanoyl chlorides was performed in phase-transfer catalysis conditions, using tetrabutylammonium chloride in a mixture of aqueous NaOH and dichloromethane. The process is particularly efficient (almost quantitative yields) as well as rapid (only 5 min reaction time, at a temperature of0°C). Taylor & Francis Group, LLC.
Palladium-catalyzed hydroesterification of alkynes employing aryl formates without the use of external carbon monoxide
Katafuchi, Yuko,Fujihara, Tetsuaki,Iwai, Tomohiro,Terao, Jun,Tsuji, Yasushi
supporting information; experimental part, p. 475 - 482 (2011/04/22)
A highly efficient hydroesterification of alkynes employing aryl formates has been developed without the use of external carbon monoxide and at ambient pressure. The reaction in the presence of a palladium-xantphos catalyst system selectively affords α,β-unsaturated esters in good to high yields. Use of an aryl formate is crucial and alkyl formates did not react at all. The hydroesterification of norbornene and terminal alkenes also readily proceeded under similar reaction conditions. A mechanistic study showed that conversion of aryl formates to carbon monoxide and phenol derivatives occurred in the hydroesterification. Xantphos is highly effective as a ligand both in the conversion of aryl formates and the hydroesterification reactions.
