1619-73-4Relevant academic research and scientific papers
A simple and efficient method for mild and selective oxidation of propargylic alcohols using TEMPO and calcium hypochlorite
Reddy, Sabbasani Rajasekhara,Chadha, Anju
, p. 14929 - 14933 (2013)
Oxidation of propargylic alcohols to the corresponding aldehydes and ketones was achieved at room temperature using 2,2,6,6-tetramethylpiperidine-1- oxyl (TEMPO) and calcium hypochlorite (Ca(OCl)2). Propargylic diols yielded corresponding dialdehydes as the product. This system was found to be very efficient for both the electron donating and electron withdrawing groups such as methoxy and nitro substituted alcohols, respectively. This method does not require any additives and demonstrates the controlled, selective oxidation of propargylic alcohols affording up to 97% isolated yield. The Royal Society of Chemistry 2013.
Chiral Phosphoric Acid-Catalyzed Enantioselective Synthesis of Pyrazole-Based Unnatural α-Amino Acid Derivatives
Woldegiorgis, Alemayehu Gashaw,Han, Zhao,Lin, Xufeng
supporting information, p. 274 - 280 (2021/11/01)
An enantioselective synthesis of unnatural pyrazole-based α-chiral amino acid derivatives from the asymmetric reaction of N-aryl-5-aminopyrazoles with β,γ-alkynyl-α-imino esters using a chiral spirocyclic phosphoric acid catalyst was developed. Using the established methodology, various pyrazole-based α-amino acid derivatives with tetrasubstituted carbon stereocenters were obtained in 67–98% yields and with 73–99% enantioselectivities. The NH2 functionality in the corresponding products enables further transformations to a chiral thiourea and a lactam. (Figure presented.).
Organocatalytic Asymmetric Dearomatization Reaction for the Synthesis of Axial Chiral Allene-Derived Naphthalenones Bearing Quaternary Stereocenters
Woldegiorgis, Alemayehu Gashaw,Han, Zhao,Lin, Xufeng
, p. 6606 - 6611 (2021/09/02)
The highly regio-, diastereo-, and enantioselective dearomatization reaction of 1-substituted 2-naphthols and β,γ-alkynyl-α-imino esters with complete atom economy is disclosed via chiral phosphoric acid catalysis. This protocol provides facile and effici
Organocatalytic Enantioselective Synthesis of Tetrasubstituted α-Amino Allenoates by Dearomative γ-Addition of 2,3-Disubstituted Indoles to β,γ-Alkynyl-α-imino Esters
Yang, Junxian,Wang, Zheng,He, Zeyuan,Li, Guofeng,Hong, Liang,Sun, Wangsheng,Wang, Rui
supporting information, p. 642 - 647 (2019/11/28)
The first asymmetric synthesis of tetrasubstituted α-amino allenoates by a chiral phosphoric acid catalyzed dearomative γ-addition reaction of 2,3-disubstituted indoles to β,γ-alkynyl-α-imino esters is reported. This method provides access to a series of
Activating Pyrimidines by Pre-distortion for the General Synthesis of 7-Aza-indazoles from 2-Hydrazonylpyrimidines via Intramolecular Diels-Alder Reactions
Le Fouler, Vincent,Chen, Yu,Gandon, Vincent,Bizet, Vincent,Salomé, Christophe,Fessard, Thomas,Liu, Fang,Houk,Blanchard, Nicolas
supporting information, p. 15901 - 15909 (2019/10/22)
Pyrimidines are almost unreactive partners in Diels-Alder cycloadditions with alkenes and alkynes, and only reactions under drastic conditions have previously been reported. We describe how 2-hydrazonylpyrimidines, easily obtained in two steps from commercially available 2-halopyrimidines, can be exceptionally activated by trifluoroacetylation. This allows a Diels-Alder cycloaddition under very mild reaction conditions, leading to a large diversity of aza-indazoles, a ubiquitous scaffold in medicinal chemistry. This reaction is general and scalable and has an excellent functional group tolerance. A straightforward synthesis of a key intermediate of Bayer's Vericiguat illustrates the potential of this cycloaddition strategy. Quantum mechanical calculations show how the simple N-trifluoroacetylation of 2-hydrazonylpyrimidines distorts the substrate into a transition-state-like geometry that readily undergoes the intramolecular Diels-Alder cycloaddition.
An Unprecedented Organocascade Synthesis of Functionalized Bicyclic Nitrones from 2-Aminomalonate Derived Nucleophiles and 1-Nitro-1,3-Enynes via Allenes Formation and Subsequent Rearrangement
Huang, Wan-Yun,Gurubrahamam, Ramani,Chen, Kwunmin
supporting information, p. 170 - 175 (2018/12/11)
An efficient organocatalytic cascade reaction for synthesising functionalized bicyclic nitrones is reported. The reaction of dielectrophilic ethyl 2-(nitromethylene)-4-arylbut-3-ynoate and (E)-diethyl 2-((2-hydroxybenzylidene)-amino)malonates to give a un
Synthesis of α-(4-Oxazolyl)amino Esters via Br?nsted Acid Catalyzed Tandem Reaction
Lee, Ansoo,Oh, Seohee,Kim, Hyunwoo
supporting information, p. 3319 - 3322 (2018/06/11)
A one-step, Br?nsted acid catalyzed tandem reaction for the synthesis of α-(4-oxazolyl)amino esters was developed. 4-Nitrobenzenesulfonic acid was found to be an efficient catalyst for the coupling of ethyl 2-oxobut-3-ynoates with amides to provide variou
Organocatalytic synthesis of densely functionalized oxa-bridged 2,6-epoxybenzo[: B] [1,5]oxazocine heterocycles
Gurubrahamam, Ramani,Nagaraju, Koppanathi,Chen, Kwunmin
supporting information, p. 6048 - 6051 (2018/06/18)
Metal-free addition of salicylhydrazones to electron deficient internal alkynes catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) to yield oxa-bridged 2,6-epoxybenzo[b][1,5]oxazocine heterocycles was achieved. The demonstrated protocol proceeds through an o-quinone methide formation, aza-Michael addition, stereoselective protonation, enamine promoted aromatization, O,O-acetalization and O,N-aminalization sequence to provide privileged heterocycles in good yields with high diastereoselectivities.
Asymmetric “Acetylenic” [3+2] Cycloaddition of Nitrones Catalyzed by Cationic Chiral PdII Lewis Acid
Honda, Kazuya,Mikami, Koichi
supporting information, p. 2838 - 2841 (2018/09/14)
Highly enantioselective [3+2] cycloaddition of ynones and nitrones has been developed. Very bulky ligand, DTBM-SEGPHOS, was used for an effective asymmetric induction over distal reaction centers on the linear ynone dipolarophile and for prevention of PdII catalyst deactivation by coordination of the nitrones. The reaction has wide scope of substrates in both ynones and nitrones.
Cationic Chiral Pd-Catalyzed “Acetylenic” Diels–Alder Reaction: Computational Analysis of Reversal in Enantioselectivity
Honda, Kazuya,Ohkura, Shun,Hayashi, Yoshihiro,Kawauchi, Susumu,Mikami, Koichi
supporting information, p. 2842 - 2846 (2018/09/25)
The highly enantioselective Diels–Alder reaction of acetylenic dienophiles is shown to be effectively catalyzed by cationic chiral palladium complexes. Not only the degree but also the sense of enantioselectivity critically depends on the steric demand of ligands. Computational analyses indicate that the steric demand does not affect the endo/exo-selectivity but the enantioface selectivity of dienes.
