Chemoselective reduction of isothiocyanates to thioformamides mediated by the Schwartz reagent

2019 ◽  
Vol 17 (7) ◽  
pp. 1970-1978 ◽  
Author(s):  
Karen de la Vega-Hernández ◽  
Raffaele Senatore ◽  
Margherita Miele ◽  
Ernst Urban ◽  
Wolfgang Holzer ◽  
...  
Keyword(s):  
Partial Reduction ◽  
Schwartz Reagent

Thioformamides are easily prepared – under full chemocontrol – through the partial reduction of isothiocyanates with the in situ generated Schwartz reagent.

A new method for the in situ generation of Cp2Zr(H)Cl (Schwartz' Reagent)

1990 ◽  
Vol 31 (50) ◽  
pp. 7257-7260 ◽  
Author(s):  
Bruce H. Lipshutz ◽  
Robert Keil ◽  
Edmund L. EIIsworth
Keyword(s):  
New Method ◽  
Schwartz Reagent ◽  
In Situ Generation

Partial Reduction of NiAl2O4 - Mechanism and the Influence of Doping

1995 ◽  
Vol 398 ◽  
Author(s):  
Z. Zhang ◽  
E. Üstündag ◽  
S.L. Sass
Keyword(s):  
Reaction Mechanism ◽  
Intermediate Stage ◽  
Reduction Reaction ◽  
Reduction Mechanism ◽  
Partial Reduction ◽  
Metal Ceramic ◽  
Mechanism And Kinetics ◽  
Equilibrium Phases ◽  
Metastable Defect

ABSTRACTMetal-ceramic microstructures were formed in situ by partial reduction of the spinel compound NiAl2O4. At 1300°C the reduction reaction passed through an intermediate stage involving the formation of Ni and metastable “defect spinel” phases, before the appearance of the equilibrium phases, Ni + α-Al2O3. At 1100°C, depending on the reduction time, the products of the reduction reaction were Ni and the metastable “defect spinel” for less than 24 hours; Ni + θ-Αl2Ο3 for 24-48 hours; and Ni + GI-AI2O3 for 144-168 hours. The effects of dopants, such as Cr2O3, MgO, TiO2 and Y2O3, on the reduction mechanism and kinetics were examined and shown, in the case of TiO2, to have a controlling influence. A reduction reaction mechanism is proposed.

scholarly journals Reduction of mixed Mn–Zr oxides: in situ XPS and XRD studies

2015 ◽  
Vol 44 (35) ◽  
pp. 15499-15507 ◽  
Author(s):  
O. A. Bulavchenko ◽  
Z. S. Vinokurov ◽  
T. N. Afonasenko ◽  
P. G. Tsyrul'nikov ◽  
S. V. Tsybulya ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Partial Reduction ◽  
Second Stage ◽  
In Situ Xps ◽  
Xrd Studies ◽  
Two Stages

The reduction of the solid solutions MnxZr1−xO2−δ proceeds via two stages. During the first stage, the Mn cations incorporated into the solid solutions MnxZr1−xO2−δ undergo partial reduction. At the second stage, Mn cations segregate on the surface.

The Carreira Synthesis of (–)-Dendrobine

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Claisen Rearrangement ◽  
Magnesium Bromide ◽  
Gel Chromatography ◽  
Ring Fusion ◽  
Enantiomerically Pure ◽  
Schwartz Reagent ◽  
Radical Reduction ◽  
Silica Gel Chromatography ◽  
Stereogenic Center

The tetracyclic alkaloid (–)-dendrobine 3 has at its core a cyclohexane that is substituted at each of its six positions, including one quaternary center. Erick M. Carreira of ETH Zürich chose (Angew. Chem. Int. Ed. 2012, 51, 3436) to assemble this ring by the Ireland-Claisen rearrangement of the lactone 1. The absolute configuration of the final product stemmed from the commercial enantiomerically pure acetonide 4, which was selectively converted to the Z-ester 5. Following the precedent of Costa, TBAF-mediated conjugate addition of 2-nitropropane to 5 proceeded with high diastereocontrol, to give, after free radical reduction, the ester 6, which was carried on the aldehyde 7. Exposure of the alkyne 9 to an in situ-generated Schwartz reagent followed by iodination gave 10 with 10:1 regioselectivity. It was possible to separate 10 from its regioisomer by careful silica gel chromatography. Metalation followed by the addition to 7 gave an intermediate that was conveniently debenzoylated with excess ethyl magnesium bromide to deliver the diol 11. Selective oxidation led to the lactone 1. Exposure of 1 to LDA and TMS-Cl induced rearrangement to the cyclohexene acid, which was esterified to give 2. Deprotection and oxidation then gave the enone 12. Cyclohexene construction by tethered Claisen rearrangement is a powerful transformation that has been little used in target-directed synthesis. Selective addition of pyrrolidine to the aldehyde of 12 generated an enamine, leading to an intramolecular Michael addition to the enone. This selectively gave the cis ring fusion, as expected, but the product was a mixture of epimers at the other newly formed stereogenic center. This difficulty was overcome by forming the enamine from N-methylbenzylamine. After cyclization, hydrogenation set the additional center with the expected clean stereocontrol, and also effected debenzylation to give 14. To close the last ring, the ketone 14 was brominated with the reagent 15, which was developed (Can. J. Chem. 1969, 47, 706) for the kinetic bromination of ketones. Exposure of the crude α-bromo ketone to 4-dimethylaminopyridine then effected cyclization to 16. Following the literature precedent, reduction of the ketone of 16 with NaBH4 followed by gentle warming led to (–)-dendrobine 3.

Ferromagnetic copper(II)–copper(II) interaction in a single chlorido and dicyanamido bridged mixed–valence copper(I/II) 2-D polymer generated by in situ partial reduction of copper(II)

2015 ◽  
Vol 68 (5) ◽  
pp. 916-927 ◽  
Author(s):  
Madhusudan Nandy ◽  
Shyamapada Shit ◽  
Piu Dhal ◽  
Corrado Rizzoli ◽  
Carlos J. Gómez–García ◽  
...  
Keyword(s):  
Mixed Valence ◽  
Partial Reduction
Sign in / Sign up

Export Citation Format

Share Document