Organocatalytic [4 + 2] cyclizations of para-quinone methide derivatives with isocyanates

2019 ◽  
Vol 17 (27) ◽  
pp. 6662-6670 ◽  
Author(s):  
Yu-Chun Cheng ◽  
Cong-Shuai Wang ◽  
Tian-Zhen Li ◽  
Feng Gao ◽  
Yinchun Jiao ◽  
...  
Keyword(s):  
Quinone Methide ◽  
Bronsted Acids ◽  
High Yields

The first [4 + 2] cyclizations of o-hydroxyphenyl-substituted p-quinone methide derivatives with isocyanates have been established under the catalysis of Brønsted acids or Brønsted bases, which efficiently constructed benzoxazin-2-one frameworks in generally high yields.

scholarly journals Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

2018 ◽  
Vol 14 ◽  
pp. 2897-2906 ◽  
Author(s):  
Stanislav V Lozovskiy ◽  
Alexander Yu Ivanov ◽  
Olesya V Khoroshilova ◽  
Aleksander V Vasilyev
Keyword(s):  
Dft Calculations ◽  
Reaction Mechanisms ◽  
Dft Study ◽  
Bronsted Acids ◽  
Allyl Alcohols ◽  
High Yields ◽  
Hydrolysis Of

In strong Brønsted acids (CF3SO3H, FSO3H, D2SO4), (arysulfonyl)allenes (ArSO2–CR1=C=CR2R3) and (arylsulfinyl)allenes (ArSO–CR1=C=CR2R3) undergo cyclization into the corresponding stable 1,2-oxathiolium ions, which were studied by means of NMR and DFT calculations. Quenching of solutions of these cations with low nucleophilic media, aqueous HCl, leads to their deprotonation with a stereoselective formation of (arysulfonyl)butadienes (for instance, ArSO2–CR1=C–C(Me)=CH2, for R2 = R3 = Me, yields of 87–98%). Reactions of (arysulfonyl)allenes in the system TfOH (0.1 equiv)–HFIP (hexafluoropropan-2-ol) followed by hydrolysis give rise to allyl alcohols (ArSO2–CR1=CH–C(OH)R2R3, yields of 78–99%). Reflux of solutions of (arysulfonyl)allenes in the presence of TfOH (1 equiv) in 1,2-dichlorobenzene leads to the cyclization into thiochromene 1,1-dioxides in high yields. Under the action of TfOH or AlX3 (X = Cl, Br) followed by hydrolysis of reaction mixtures, (arylsulfinyl)allenes give allyl alcohols (ArSO2–CR1=CH–C(OH)R2R3). Plausible reaction mechanisms have been proposed for all studied reactions.

The Acceleration of the Rearrangement of α-Hydroxy Aldimines by Lewis or Brønsted Acids

Synlett ◽  
2018 ◽  
Vol 29 (15) ◽  
pp. 2015-2018 ◽  
Author(s):  
William Wulff ◽  
Xin Zhang ◽  
Yijing Dai
Keyword(s):  
Silica Gel ◽  
Efficient Method ◽  
Bronsted Acids ◽  
High Yields

An efficient method was developed for the synthesis of α-amino ketones from α-hydroxy imines. The reaction occurs through an α-iminol rearrangement involving the migration of a substituent of the carbinol carbon to the imine carbon. The optimal catalysts were found to be silica gel or montmorillonite K 10, which effected migration of a variety of aryl and alkyl substituents in high yields. The rearrangement can also be carried out on imines generated in situ from aldehydes and amines in essentially the same yields as those from the preformed imines.

scholarly journals N-Triflylphosphorimidoyl Trichloride: A Versatile Reagent for the Synthesis of Strong Chiral Brønsted Acids

Synlett ◽  
2017 ◽  
Vol 28 (12) ◽  
pp. 1478-1480 ◽  
Author(s):  
Benjamin List ◽  
Sunggi Lee ◽  
Philip Kaib
Keyword(s):  
Bronsted Acids ◽  
Sterically Hindered ◽  
High Yields ◽  
Chiral Brønsted Acids ◽  
Versatile Reagent

A series of strong Brønsted acids has been synthesized in high yields using N-triflylphosphorimidoyl trichloride as reagent. The syntheses proceed efficiently with electron-rich, electron-deficient, and sterically hindered substrates.

Construction of chiral chroman scaffolds via catalytic asymmetric (4 + 2) cyclizations of para-quinone methide derivatives with 3-vinylindoles

2020 ◽  
Vol 18 (28) ◽  
pp. 5388-5399 ◽  
Author(s):  
Shu-Fang Wu ◽  
Man-Su Tu ◽  
Qing-Qing Hang ◽  
Shu Zhang ◽  
Haixia Ding ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Quinone Methide ◽  
Title Reaction ◽  
Chiral Phosphoric Acid ◽  
Catalytic Asymmetric ◽  
High Yields

The title reaction has been established in the presence of chiral phosphoric acid, affording chiral chroman derivatives bearing an indole moiety in high yields and with moderate to good stereoselectivities.

Application of Benzofuran-Derived Azadienes as Two-Carbon Building Blocks in Annulations: Chemo- and Diastereoselective Construction of Spiro-Benzofuran Scaffolds

Synthesis ◽  
2020 ◽  
Author(s):  
Jin-Peng Zhang ◽  
Wei Tan ◽  
Feng Shi ◽  
Ye-Xin Wang ◽  
Yi-Nan Lu ◽  
...  
Keyword(s):  
Building Blocks ◽  
Quinone Methide ◽  
High Yields

A base-promoted (2+4) annulation of benzofuran-derived azadienes with para-quinone methide derivatives has been established, which afforded spiro-benzofuran derivatives in generally high yields (57–97%) and with good diastereoselectivities (85:15 to >95:5 dr). This reaction not only represents the first application of benzofuran-derived azadienes as two-carbon building blocks in annulations, but also provides an efficient protocol for the construction of spiro-benzofuran scaffolds with chemoselectivity and high diastereoselectivity. This approach will enrich the chemistry of benzofuran-derived azadiene-involved reactions.

Phosphine-catalyzed [4 + 2] cyclization of para-quinone methide derivatives with allenes

2019 ◽  
Vol 17 (9) ◽  
pp. 2361-2369 ◽  
Author(s):  
Fu-Ru Yuan ◽  
Fei Jiang ◽  
Ke-Wei Chen ◽  
Guang-Jian Mei ◽  
Qiong Wu ◽  
...  
Keyword(s):  
Quinone Methide ◽  
Phosphine Catalysis ◽  
High Yields

The first [4 + 2] cyclization of para-quinone methide derivatives with allenes has been established via phosphine catalysis, which afforded a series of chroman derivatives in high yields (up to 97%) and excellent (E/Z)-selectivities (all >95 : 5 E/Z).

Brønsted Acids of Anionic Chiral Cobalt(III) Complexes as Catalysts for the Iodoglycosylation or Iodocarboxylation of Glycals

Synlett ◽  
2019 ◽  
Vol 30 (09) ◽  
pp. 1077-1084
Author(s):  
Rui Wang ◽  
Wen-Qiang Wu ◽  
Na Li ◽  
Jia Shen ◽  
Kun Liu ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Phase Transfer ◽  
Bronsted Acids ◽  
Phase Transfer Catalysts ◽  
Biological Importance ◽  
High Yields

Brønsted acids of anionic chiral Co(III) complexes were found to act as efficient phase-transfer catalysts for the diastereoselective iodoglycosylation or iodocarboxylation of glycals with a variety of alcohols or carboxylic acids, respectively, with N-iodosuccinimide as the iodo cation source. The corresponding 2-deoxy-2-iodoglycosides, including monosaccharides and disaccharides, and 2-deoxy-2-iodoglycosyl carboxylates, which are of high synthetic and biological importance, were obtained in high yields (up to 88%) with good diastereoselectivities (up to 9:1 dr).

scholarly journals Asymmetric synthesis of chromene skeletons via organocatalytic domino reactions of in situ generated ortho-quinone methide with malononitrile and β-functionalized ketone

RSC Advances ◽  
2017 ◽  
Vol 7 (62) ◽  
pp. 39216-39220 ◽  
Author(s):  
Lili Zhang ◽  
Xiao Zhou ◽  
Pengfei Li ◽  
Zhantao Liu ◽  
Yang Liu ◽  
...  
Keyword(s):  
Asymmetric Synthesis ◽  
Quinone Methide ◽  
Domino Reactions ◽  
Quinone Methides ◽  
High Yields

Enantioselective organocatalytic domino reactions of in situ generated ortho-quinone methides with malononitrile and β-functionalized ketones have been developed. This strategy could generate various chiral chromenes in high yields and stereoselectivities.

A Simple Method for Preparing Fibrinogen

1966 ◽  
Vol 16 (01/02) ◽  
pp. 198-206 ◽  
Author(s):  
W Straughn ◽  
R. H Wagner
Keyword(s):  
Barium Sulfate ◽  
Caproic Acid ◽  
Aminobutyric Acid ◽  
Gamma Aminobutyric Acid ◽  
Human Fibrinogen ◽  
Simple Method ◽  
High Yields ◽  
Marked Stability

SummaryA simple new procedure is reported for the isolation of canine, bovine, porcine, and human fibrinogen. Two molar β-alanine is used to precipitate fibrinogen from barium sulfate adsorbed plasma. The procedure is characterized by dependability and high yields. The material is 95% to 98% clottable protein but still contains impurities such as plasminogen and fibrin-stabilizing factor. Plasminogen may be removed by adsorption with charcoal. The fibrinogen preparations exhibit marked stability to freezing, lyophilization, and dialysis. Epsilon-amino-n-caproic acid and gamma-aminobutyric acid which were also studied have the property of precipitating proteins from plasma but lack the specificity for fibrinogen found with β-alanine.

A Novel Method for the Rapid Purification of Human and Rat Fibrin(OGEN) Degradation Products in High Yields

1979 ◽  
Author(s):  
W. Nieuwenhuizen ◽  
I. A. M. van Ruijven-Vermeer ◽  
F. Haverkate ◽  
G. Timan
Keyword(s):  
Degradation Products ◽  
Complete Separation ◽  
Purification Method ◽  
Amino Terminal ◽  
Novel Method ◽  
Rapid Purification ◽  
The One ◽  
High Yields ◽  
Size Heterogeneity ◽  
D Dimer

A novel method will be described for the preparation and purification of fibrin(ogen) degradation products in high yields. The high yields are due to two factors. on the one hand an improved preparation method in which the size heterogeneity of the degradation products D is strongly reduced by plasmin digestion at well-controlled calcium concentrations. At calcium concentrations of 2mM exclusively D fragments, M.W.= 93-000 (Dcate) were formed; in the presence of 1OmM EGTA only fragments M.W.= 80.000 (D EGTA) were formed as described. on the other hand a new purification method, which includes Sephadex G-200 filtration to purify the D:E complexes and separation of the D and E fragments by a 16 hrs. preparative isoelectric focussing. The latter step gives a complete separation of D (fragments) (pH = 6.5) and E fragments (at pH = 4.5) without any overlap, thus allowing a nearly 100% recovery in this step. The overall recoveries are around 75% of the theoretical values. These recoveries are superior to those of existing procedures. Moreover the conditions of this purification procedure are very mild and probably do not affect the native configuration of the products. Amino-terminal amino acids of human Dcate, D EGTA and D-dimer are identical i.e. val, asx and ser. in the ratgly, asx and ser were found. E 1% for rat Dcate=17-8 for rat D EGTA=16.2 and for rat D- dimer=l8.3. for the corresponding human fragments, these values were all 20.0 ± 0.2.

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