Reduction cyclization of C60 with ketene under solvent free mechanical grinding

In traditional chemical organic reactions, most of the reactions need to use a large number of toxic and harmful solvents, which brings serious harm to the health and environment of the experimenters In order to solve this problem, solvent-free mechanochemistry has been introduced into organic synthesis The earliest such fullerene reaction was completed by Wang Guanwu et al In 1996, the solvent-free reformatsky reaction of fullerene was realized (chem Commun 1996, 2059-2060) In 1997, Wang Guanwu and others accidentally obtained the dumbbell shaped molecule C 120 (nature 1997, 387, 583-586) under the condition of solvent-free mechanical grinding, which is the first time to prepare, separate and identify C 120 by chemical method In the next 20 years, all kinds of reactions were successfully realized under the condition of solvent-free mechanical grinding Wang Guanwu summarized his research progress in fullerene chemistry and organic small molecule reactions, and published a review article in the mechanochemistry of chem SOC Rev 2013, 42, 7668-7700; chem SOC Rev 2013, 42, 7535-7570 Recently, Professor Wang Guanwu's research group used cheap and easily available zinc as reducing agent to realize the reduction cyclization reaction of C60 and ketene under the condition of solvent-free mechanical grinding, and obtained a series of fullerene Cyclopentanol derivatives, whose products can also be dehydrated to obtain the corresponding fullerene cyclopentene derivatives Relevant research results were published in org Lett (DOI: 10.1021/acs.orglett.9b00612) Wang Guanwu was studied in the Department of chemistry, Lanzhou University from September 1983 to June 1993 He obtained bachelor's degree, master's degree and doctor's degree respectively From July 1993 to April 2000, he successively engaged in postdoctoral research at Fudan University, Kyoto University, Kentucky University, University of Chicago and Yale University In May 2000, he was introduced to the Department of chemistry, University of science and technology of China through the "hundred talents plan" of Chinese Academy of Sciences in 1999 Winner of National Science Fund for Distinguished Young Scholars in 2001; now deputy editor in chief of mini reviews in Organic Chemistry (2017 present), editorial board member of Organic Chemistry (2007 present), current organic chemistry (2014 present), Journal of Chemistry (2015 present), current organic chemistry (2016 present) In 2004, he was selected as one of the first batch of national candidates for the "one million talents project in the new century" of seven ministries and commissions; in 2005, he was awarded the "seventh Anhui Youth Science and Technology Award" by the Organization Department of Anhui provincial Party committee, the Department of personnel of Anhui Province, and the Anhui Science and Technology Association; in 2005, he was granted the special allowance of the State Council; in 2007, he was awarded the "Wuxi apptec Life Chemistry Research Award"; in 2012, he was awarded the Asian award Core Program Lectureship Award; in 2017, he was interviewed by the chemical promotion center of the Ministry of science and technology of Taiwan (Visiting Lectureship) In recent years, research achievements have been made in the fields of fullerene chemistry and green chemistry, such as fullerene mechanochemistry, fullerene free radical chemistry, fullerene electrochemistry, solvent-free organic synthesis, C-H bond activation, etc., including nature, J am Chem SOC., angel Chem Int ed., ACS catalyst., Chem SCI., org Lett., chem Commin., chem EUR J More than 210 articles were published in famous journals Cutting edge scientific research achievements: fullerene is a kind of electron deficient substance, known as "free radical sponge", which is easy to be attacked by other electron rich reagents, but it is difficult to attack other reagents by itself However, it becomes a fullerene anion after receiving electrons, which is nucleophilic Compared with other chemical or electrochemical methods, fullerene anion can be prepared by active metal in solvent-free mechanical grinding Based on the above research, the author successfully realized the reaction of C60 with alkene ketone (α, β - unsaturated carbonyl compounds) under the condition of mechanical grinding and solvent-free by using cheap and commercial zinc powder as reducing agent Fig 1 Reduction cyclization of C60 and ketene (source: org Lett.) first, the author used C60, zinc powder and chalcone 1A as starting materials to screen the reaction It was found that the reaction can only be started under the action of water At the same time, a small number of two different products were separated, one is alkylated fullerene hydrogen, the other is fullerene Cyclopentanol derivative According to the structure inference, the author speculates that alkylated fullerene hydrogen is the reaction intermediate and can be converted into the final product under the action of alkali Through a series of screening conditions, the author finally determined the reaction conditions for the production of fullerene Cyclopentanol derivatives by one pot two-step method alone, with the final yield of 42% (Figure 2) Figure 2 Screening of reaction conditions (source: org Lett.) then, the author examined the substrate applicability of the reaction (Figure 3) When the aromatic ring of chalcone was replaced by halogen, methyl and methoxy, the reaction proceeded smoothly and the corresponding products were obtained In addition, the reaction can also be compatible with other types of ketene, such as heterocycles, naphthalene rings, methyl and dimethylsubstituted substrates Figure 3 Substrate development (source: org Lett.) further, in order to determine the reaction mechanism, the author conducted a series of control experiments (Figure 4) Fullerene hydrogen and the final product can be separated by the reaction without adding alkali Fullerene hydrogen can be efficiently transformed into product under the action of alkali, that is to say, fullerene hydrogen is determined as the intermediate Secondly, the author uses deuterium water instead of water, and finds that fuller hydrogen and the product are deuterium, indicating that water is the proton source of the reaction As zinc powder can also reduce alkene ketone to generate corresponding free radicals, polysubstituted Cyclopentanol can be obtained without adding C60, the source of which is the coupling of chalcone free radicals; however, its formation was not observed when adding C60, that is to say, the possibility of the existence of chalcone free radicals in this reaction was excluded Fig 4 Control experiment (source: org Lett.) based on the above control experiment, the author proposed the possible reaction mechanism (Fig 5) Firstly, C60 is reduced to C602 -, and then C602 - reacts with alkene ketone by Michael addition to form RC 60 -, and then the intramolecular nucleophilic reaction takes place to obtain the final product The intermediate is produced by the reaction of part of RC 60 - reacts with water to form fullerene hydrogen, which can be converted into product under alkaline condition Figure 5 Possible reaction mechanism (source: org Lett.) finally, through dehydration experiment, the author found that fullerene cyclopentene can be formed by fullerene Cyclopentanol under the joint action of acid and anhydrous magnesium sulfate Taking products 2a and 2b as examples, the corresponding products 6A (91%) and 6B (84%) can be obtained with high yield under the condition of ball milling Fig 6 Dehydration experiment (source: org Lett.) Professor Wang Guanwu's research group reported a reaction of [60] fullerenes and ketenes under solvent-free and ball milling conditions, and obtained a series of fullerenes and Cyclopentanol derivatives, which can be dehydrated to form fullerenes and cyclopentenes under ball milling conditions This method not only has a good range of substrate application, but also uses cheap and easy to get raw materials, and is easy to operate At the same time, it provides a new idea and strategy for the synthesis of fullerene derivatives under the condition of mechanical grinding This article was recently published in org Lett (DOI: 10.1021 / ACS Orglett 9b00612) Liu Hongwei, a graduate student of the University of science and technology of China, is the first author of this paper, and Professor Wang Guanwu is the corresponding author Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeangoapp, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.