Reduction (3 + 2) cyclization of benzoyl and pyran salt

In recent years, the redox adducts of o-dicarbonyl compounds and trivalent phosphine reagents have become a very important class of α - carbonyl carbene analogues, which are used in a series of cyclization reactions different from traditional ones, such as (1 + 4) cyclization to construct dihydrofuran ring However, in the reported cyclization reactions, such active intermediates are mainly derived from α - ketoacids and are only used as C1 synthesis modules Recently, Wang Rixin's research group of East China Normal University successfully explored the C3 synthesis module function of this kind of active intermediate by using the subsequent rearrangement reaction caused by the strong nucleophilic ability of carbonyl oxygen in the phosphine adducts derived from benzoyl compounds, and found the reduction (3 + 2) cyclization reaction between the active intermediate of this kind of adducts and pyran salt It is worth pointing out that in this reaction, a challenging CIS chalcone polysubstituted furan analogue was synthesized stereoselectively under mild conditions The results were published in org Lett (DOI: 10.1021/acs.orglett.9b02182) Introduction to Professor Wang Rixin: sunewang R Wang, professor and doctoral supervisor of East China Normal University, young scholar of "Zijiang" of East China Normal University, and Humboldt scholar of Germany Mainly engaged in the study of elemental organic and organometallic chemistry He received his bachelor's degree from Shanghai Jiaotong University in 2006, master's degree from Shanghai Institute of organic chemistry, Chinese Academy of Sciences in 2009, and doctor's degree from Chinese University of Hong Kong in 2012 Later, he engaged in postdoctoral research in PSU, UCSD and University of welzburg, Germany In June 2018, he joined Chuang Changgong Institute of Shanghai Institute of organic chemistry, Chinese Academy of Sciences, East China Normal University So far, 10 SCI papers have been published in J am Chem SOC And angelw Chem Int ed (Signature: sunwang R Wang) Due to the needs of scientific research, the research group is looking for one postdoctoral and several research assistants For more information, please pay attention to the website of the research group: https://faculty.ecnu.edu.cn/s/3887/main.jspy Cutting edge scientific research achievements: reduction (3 + 2) cyclization of benzoyl and pyranoate in order to avoid the interference of reaction between trivalent phosphine and pyranoate, the author first dissolved P (NME 2) 3 and benzoyl in acetonitrile solvent, and then added pyranoate into the reaction solution (Figure 1) The reaction system changed from light yellow to red immediately After several minutes, the reaction precipitated The yellow solid with 63% yield was obtained by column chromatography, and its structure was confirmed to be CIS chalcone substituted by furan by crystal diffraction data of similar products In view of the fact that the raw material benzoyl can not be completely converted, the author has instead optimized the reaction conditions with pyranoate as the limited reagent When using 1.2 equivalent benzoyl and 1.1 equivalent P (NME 2) 3, the author was able to separate the target compound 4 in 70% yield (Table 1) Fig 1 P (NME 2) 3-mediated reaction of benzoyl with 2,6-diphenylpyranoate (source: org Lett.) table 1 Condition optimization (source: org Lett.) after determining the optimal reaction conditions, the author first studied the substrate range of 2,6-disubstituted pyranoate (Fig 2) Although the reaction efficiency of electron rich aromatic ring substituted pyranes is slightly poor, most of the reactions of para -, meta -, and ortho functionalized aromatic and alkyl substituted pyranes and benzoyls can achieve medium to good yields Figure 2 Substrate range of pyranoate (source: org Lett.) next, the author studied the substrate applicability of symmetric and asymmetric benzoyl Different from the substituent effect of pyranoate, the substituent of benzoyl group shows obvious electronic effect and steric resistance effect (Fig 3) In particular, para - or meta alkyl, halogenated, and alkynyl substituted benzoyls exhibit similar reactivity to unsubstituted benzoyls However, the activity of 4,4 '- dimethoxy benzoyl is very low, and the BIS ortho substituted benzoyl is almost non reactive Based on the remarkable substituent effect of the reaction, the selective cyclization of asymmetric benzoyl was studied, which further expanded the diversity of product structure It should be noted that the reaction is still limited to o-dicarbonyl benzoyl compounds Fig 3 Substrate range of benzoyl (source: org Lett.) although the cyclization takes place on the 2,3-position double bond of pyranoate, the (3 + 2) cyclization cannot take place on the 4-position substituted pyranoate For example, 2,4,6-triphenylpyran salt is hydrolyzed under reaction conditions (formula 1) Considering the importance of 4-substituents, the author proposed the possible reaction mechanism of 3,4-double bond cyclopropane intermediates (Fig 4) Although the author has not been able to separate or detect the reaction intermediates involved, the author indirectly proved the feasibility of the proposed reaction mechanism through the electrophilic cyclization of cyclopropane and 3,4-dihydropyranoate intermediates promoted by trifluoromethylsulfonic acid (Fig 5) (source: org Lett.) Fig 4 Possible reaction mechanism (source: org Lett.) Fig 5 Preparation of cyclopropynone and tfoh promoted reaction (source: org Lett.) this achievement was recently published on organic letters (DOI: 10.1021/acs.org TT 9b02182) The author of this paper is: Pengwei tan (Tan Pengwei), sunwang R Wang * (Wang Rixin) The research work was supported by East China Normal University 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 website, chembeangoapp, chembeango official micro blog, CBG information wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the representative research groups in China, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit