ChemInform Abstract: Polymer-Supported Dicyanoketene Acetal as a π-Acid Catalyst: Monothioacetalization and Carbon-Carbon Bond Formation of Acetals.

ChemInform ◽  
2000 ◽  
Vol 31 (49) ◽  
pp. no-no
Author(s):  
Nobuyuki Tanaka ◽  
Tsuyoshi Miura ◽  
Yukio Masaki
Keyword(s):  
Bond Formation ◽  
Acid Catalyst ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Polymer Supported

scholarly journals The two-step mechanochemical synthesis of porphyrins

2014 ◽  
Vol 170 ◽  
pp. 59-69 ◽  
Author(s):  
Hannah Shy ◽  
Paula Mackin ◽  
Andrea S. Orvieto ◽  
Deepa Gharbharan ◽  
Geneva R. Peterson ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Mechanochemical Synthesis ◽  
Bond Formation ◽  
Acid Catalyst ◽  
Solvent Free ◽  
Oxidizing Agent ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Solvent Free Conditions ◽  
Porphyrin Synthesis

Porphyrin synthesis under solvent-free conditions represents the “greening” of a traditional synthesis that normally requires large amounts of organic solvent, and has hindered the industrial-scale synthesis of this useful class of molecules. We have found that the four-fold acid-catalysed condensation of aldehyde and pyrrole to yield a tetra-substituted porphyrin is possible through mechanochemical techniques, without a solvent present. This represents one of the still-rare examples of carbon–carbon bond formation by mechanochemistry. Specifically, upon grinding equimolar amounts of pyrrole and benzaldehyde in the presence of an acid catalyst, cyclization takes place to give reduced porphyrin precursors (reversible), which upon oxidation form tetraphenylporphyrin (TPP). The approach has been found to be suitable for the synthesis of a variety of meso-tetrasubstituted porphyrins. Oxidation can occur either by using an oxidizing agent in solution, to give yields comparable to those published for traditional methods of porphyrin synthesis, or through mechanochemical means resulting in a two-step mechanochemical synthesis to give slightly lower yields that are still being optimized. We are also working on “green” methods of porphyrin isolation, including entrainment sublimation, which would hopefully further reduce the need for large amounts of organic solvent. These results hold promise for the development of mechanochemical synthetic protocols for porphyrins and related classes of compounds.

Carbon Dioxide-Mediated C(sp2)–H Arylation of Primary and Secondary Benzylamines

2018 ◽  
Author(s):  
Mohit Kapoor ◽  
Pratibha Chand-Thakuri ◽  
Michael Young
Keyword(s):  
Carbon Dioxide ◽  
Transition Metal ◽  
Bond Activation ◽  
Bond Formation ◽  
Carbon Bond ◽  
Chelate Effect ◽  
Free Amine ◽  
Carbon Carbon Bond ◽  
New Strategy ◽  
Metal Catalyzed

Carbon-carbon bond formation by transition metal-catalyzed C–H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of <i>ortho</i>-arylbenzylamines, however, effective <i>ortho</i>-C–C bond formation from C–H bond activation of free primary and secondary benzylamines using Pd<sup>II</sup> remains an outstanding challenge. Presented herein is a new strategy for constructing <i>ortho</i>-arylated primary and secondary benzylamines mediated by carbon dioxide (CO<sub>2</sub>). The use of CO<sub>2</sub> is critical to allowing this transformation to proceed under milder conditions than previously reported, and that are necessary to furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, a chelate effect is demonstrated to facilitate selective monoarylation.

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