1914-05-2Relevant academic research and scientific papers
Palladium-catalyzed selective N -allylation of indoles assisted by PEG-water system
Peng, Bai-Jing,Huang, Yi-Ting,Fül?p, Ferenc,Lin, I-Ling,Yang, Shyh-Chyun
, p. 11549 - 11553 (2019)
The synthesis of N-allylic indoles is of great interest because of their potential biological properties. It is a true challenge to develop new methods for the N-allylation of indoles due to the favorable C3-allylation. We uncovered a new strategy to synthesize N-allylic indoles via a palladium catalyst as a promoting agent, providing the N-allylated indoles in high yields. In addition, the organic reaction with polyethylene glycol (PEG) in water is one of the key emerging strategies that is currently attracting tremendous attention, which is intended to provide alternative eco-friendly and efficient ways for the construction of covalent bonds. In this study, the palladium-catalyzed indoles with allylic acetates in a PEG-water system were investigated under various conditions. This system provides a simple, convenient, and efficient way to afford a high yield of N-allylated indoles.
Synthesis of pyrroloindolines through formal [3 + 2]-cycloaddition of indoles with chiral N-2-acetamidoacrylyl oxazolidinones
Smith, Isaac T.,Neeley, Jared B.,Brinley, Tanner D.,Fullmer, Peter R.,Andrus, Merritt B.
supporting information, (2020/05/01)
Chiral N-2-acetamidoacrylyl oxazolidinones were produced and reacted with indoles under Lewis acid conditions to generate hexahydropyrrolo[2,3-b]indole products in a formal [3 + 2] cycloaddition process. Optimal conditions included the use of tin(IV) chloride in methylene chloride at 0 °C. Pyrroloindoline products were obtained from various indoles with shorter reaction times (12 hr) up to 91% yield with high, >20:1 exo selectivity. A mechanism involving reversible conjugate addition followed by an enamine lone-pair-iminium capture, tautomerization, and tin-enolate protonation accounts for the selectivity. The method enables selective applications to pyrroloindoline targets and further refinement with chiral catalysts.
Synthesis of Pyrido[2,3-b]indole Derivatives via Rhodium-Catalyzed Cyclization of Indoles and 1-Sulfonyl-1,2,3-triazoles
An, Yuehui,Chen, Yidian,Duan, Shengguo,Li, Chuan-Ying,Xu, Ze-Feng,Xue, Bing,Zhang, Wan
supporting information, (2020/04/22)
Acyloxy-substituted α,β-unsaturated imines generated in situ from triazoles can act as aza-[4 C] synthons and be trapped by indoles in a stepwise [4 + 2] cycloaddition reaction, thus providing rapid access to valuable pyrido[2,3-b]indoles in high yields. Attractive features of this reaction system include operational simplicity, readily available substrates, construction of sterically demanding quaternary centers, and convenient derivatization using triflate. (Figure presented.).
Platinum-catalyzed selective N-allylation of 2,3-disubstituted indoles with allylic acetates in water
Peng, Bai-Jing,Hsueh, Wen-Ting,Fül?p, Ferenc,Yang, Shyh-Chyun
supporting information, p. 58 - 62 (2019/01/04)
Due to their biological activity, indoles and substituted indoles have attracted considerable attention from both synthetic and medicinal scientists. Much effort has been directed toward the development of methods for the functionalization of the indole nucleus. The protocol uses a catalytic amount of catalyzed platinum as a promoting agent, producing N-allylated indoles in considerable yields. Moreover, water, with its large heat capacity, is one of the most abundant molecules on earth. The use of water as a solvent may bring about many environmental benefits. Herein, we have demonstrated that the platinum-catalyzed selective N-allylation of 2,3-disubstituted indoles proceeds in water. This method provides a simple, convenient, and efficient way to afford a high yield of N-allylated indoles.
Harnessing the Polarizability of Conjugated Alkynes toward [2 + 2] Cycloaddition, Alkenylation, and Ring Expansion of Indoles
Pradhan, Tapas R.,Kim, Hong Won,Park, Jin Kyoon
supporting information, p. 5286 - 5290 (2018/09/12)
Reported is the utilization of electronically biased conjugated alkynes in the development of highly diastereo- and regioselective dearomative [2 + 2] cycloadditions, alkenylations, and ring expansions of electron-rich indoles. Regioselective protonations of cross- and linear-conjugated alkynes were found to be crucial for accessing various cyclobutene-fused indoline and alkenylated indole derivatives. Furthermore, the facile ring expansion of [2 + 2] keto adducts, which were successfully synthesized from ynones, provided 1H-benzo[b]azepine scaffolds.
Platinum-catalyzed allylation of 2,3-disubstituted indoles with allylic acetates
Peng, Bai-Jing,Wu, Wen-Ting,Yang, Shyh-Chyun
, (2018/01/17)
Given the importance of heterocycle indole derivatives, much effort has been directed toward the development of methods for functionalization of the indole nucleus at N1 and C3 sites. Moreover, the platinum-catalyzed allyation of nucleophiles was an established and efficient way, which has been applied to medicinal and organic chemistry. In our research, the platinum-catalyzed 2,3-disubstitued indoles with allylic acetates was investigated under different conditions. Herein, we established a simple, convenient, and efficient method, which afforded high yield of allylated indoles.
Electron-Transfer and Hydride-Transfer Pathways in the Stoltz–Grubbs Reducing System (KOtBu/Et3SiH)
Smith, Andrew J.,Young, Allan,Rohrbach, Simon,O'Connor, Erin F.,Allison, Mark,Wang, Hong-Shuang,Poole, Darren L.,Tuttle, Tell,Murphy, John A.
supporting information, p. 13747 - 13751 (2017/10/12)
Recent studies by Stoltz, Grubbs et al. have shown that triethylsilane and potassium tert-butoxide react to form a highly attractive and versatile system that shows (reversible) silylation of arenes and heteroarenes as well as reductive cleavage of C?O bonds in aryl ethers and C?S bonds in aryl thioethers. Their extensive mechanistic studies indicate a complex network of reactions with a number of possible intermediates and mechanisms, but their reactions likely feature silyl radicals undergoing addition reactions and SH2 reactions. This paper focuses on the same system, but through computational and experimental studies, reports complementary facets of its chemistry based on a) single-electron transfer (SET), and b) hydride delivery reactions to arenes.
Regioselective N-allylation and N-cinnamylation of indoles using CuI-exchanged hierarchical nanoporous material
Senthilkumar,Kumarraja
supporting information, p. 86 - 89 (2015/08/24)
Regioselective N-allylation and N-cinnamylation of indoles are achieved using a novel catalyst of CuI-exchanged hierarchically architectured nanoporous material (MMZCuIY). The catalyst was characterized by electron microscopy and X-ray methods. Other advantages like functional tolerance, easy separation and reusability of the catalyst are also highlighted.
Microwave-assisted facile synthesis of [a]-annelated pyrazolopyrroloindoles via intramolecular azomethine imine 1,3-dipolar cycloaddition
Shinde, Anand H.,Vidyacharan, Shinde,Sharada, Duddu S.
supporting information, p. 3064 - 3069 (2014/05/20)
The synthesis of [a]-annelated pyrazolopyrroloindoles via intramolecular 1,3-dipolar cycloaddition of in situ generated azomethine imine from N-allylated indole-2-carboxaldehyde, in regio- and stereoselective manner by using microwave irradiation is described. A one-pot strategy for the expedient synthesis of pyrazolopyrroloindoles has been developed.
Enantioselective TADMAP-catalyzed carboxyl migration reactions for the synthesis of stereogenic quaternary carbon
Shaw, Scott A.,Aleman, Pedro,Christy, Justin,Kampf, Jeff W.,Va, Porino,Vedejs, Edwin
, p. 925 - 934 (2007/10/03)
The chiral, nucleophilic catalyst TADMAP [1, 3-(2,2,2-triphenyl-1- acetoxyethyl)-4-(dimethylamino)-pyridine] has been prepared from 3-lithio-4-(dimethylamino)pyridine (5) and triphenylacetaldehyde (3), followed by acylation and resolution. TADMAP catalyzes the carboxyl migration of oxazolyl, furanyl, and benzofuranyl enol carbonates with good to excellent levels of enantioselection. The oxazole reactions are especially efficient and are used to prepare chiral lactams (23) and lactones (30) containing a quaternary asymmetric carbon. TADMAP-catalyzed carboxyl migrations in the indole series are relatively slow and proceed with inconsistent enantioselectivity. Modeling studies (B3LYP/6-31G*) have been used in qualitative correlations of catalyst conformation, reactivity, and enantioselectivity.
