A Surprising Substituent Effect Provides a Superior Boronic Acid Catalyst for Mild and Metal-Free Direct Friedel-Crafts Alkylations and Prenylations of Neutral Arenes

2015 ◽  
Vol 21 (11) ◽  
pp. 4218-4223 ◽  
Author(s):  
Carolynne L. Ricardo ◽  
Xiaobin Mo ◽  
J. Adam McCubbin ◽  
Dennis G. Hall
Keyword(s):  
Boronic Acid ◽  
Substituent Effect ◽  
Acid Catalyst ◽  
Metal Free

scholarly journals Recent Advances in Transition-Metal-Free (4+3)-Annulations

Synthesis ◽  
2021 ◽  
Author(s):  
Heather Lam ◽  
Mark Lautens ◽  
Xavier Abel-Snape ◽  
Martin F. Köllen
Keyword(s):  
Transition Metal ◽  
Boronic Acid ◽  
Lewis Acids ◽  
Acid Catalysis ◽  
Heterocyclic Carbenes ◽  
Bronsted Acids ◽  
Metal Free ◽  
Previous Review ◽  
Dual Activation ◽  
Metal Catalyzed

Abstract(4+3)-Annulations are incredibly versatile reactions which combine a 4-atom synthon and a 3-atom synthon to form both 7-membered carbocycles as well as heterocycles. We have previously reviewed transition-metal-catalyzed (4+3)-annulations. In this review, we will cover examples involving bases, NHCs, phosphines, Lewis and Brønsted acids as well as some rare examples of boronic acid catalysis and photocatalysis. In analogy to our previous review, we exclude annulations involving cyclic dienes like furan, pyrrole, cyclohexadiene or cyclopentadiene, as Chiu, Harmata, Fernándes and others have recently published reviews encompassing such substrates. We will however discuss the recent additions (2010–2020) to the literature on (4+3)-annulations involving other types of 4-atom-synthons.1 Introduction2 Bases3 Annulations Using N-Heterocyclic Carbenes3.1 N-Heterocyclic Carbenes (NHCs)3.2 N-Heterocyclic Carbenes and Base Dual-Activation4 Phosphines5 Acids5.1 Lewis Acids5.2 Brønsted Acids6 Boronic Acid Catalysis and Photocatalysis7 Conclusion

scholarly journals 1,3-Dioxolan-4-Ones as Promising Monomers for Aliphatic Polyesters: Metal-Free, in Bulk Preparation of PLA

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2396
Author(s):  
Stefano Gazzotti ◽  
Marco Aldo Ortenzi ◽  
Hermes Farina ◽  
Alessandra Silvani
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Acid Catalyst ◽  
Monomer Conversion ◽  
Reaction Conditions ◽  
Aliphatic Polyesters ◽  
Metal Free ◽  
Weight Growth ◽  
Double Activation

The first example of solvent-free, organocatalyzed, polymerization of 1,3-dioxolan-4-ones, used as easily accessible monomers for the synthesis of polylactic acid (PLA), is described here. An optimization of reaction conditions was carried out, with p-toluensulfonic acid emerging as the most efficient Brønsted acid catalyst. The reactivity of the monomers in the tested conditions was studied following the monomer conversion by 1H NMR and the molecular weight growth by SEC analysis. A double activation polymerization mechanism was proposed, pointing out the key role of the acid catalyst. The formation of acetal bridges was demonstrated, to different extents depending on the nature of the aldehyde or ketone employed for lactic acid protection. The polymer shows complete retention of stereochemistry, as well as good thermal properties and good polydispersity, albeit modest molecular weight.

Regio- and stereoselective β-mannosylation using a boronic acid catalyst and its application in the synthesis of a tetrasaccharide repeating unit of lipopolysaccharide derived from E. coli O75

2017 ◽  
Vol 53 (21) ◽  
pp. 3018-3021 ◽  
Author(s):  
Nobuya Nishi ◽  
Junki Nashida ◽  
Eisuke Kaji ◽  
Daisuke Takahashi ◽  
Kazunobu Toshima
Keyword(s):  
Boronic Acid ◽  
Acid Catalyst ◽  
E Coli

A novel regio- and stereoselective β-mannosylation using 1,2-anhydromannose and a diol sugar acceptor in the presence of a boronic acid catalyst and its application are reported.

Metal-free electrocatalyst for reducing nitrogen to ammonia using a Lewis acid pair

2019 ◽  
Vol 7 (9) ◽  
pp. 4865-4871 ◽  
Author(s):  
Li Shi ◽  
Qiang Li ◽  
Chongyi Ling ◽  
Yehui Zhang ◽  
Yixin Ouyang ◽  
...  
Keyword(s):  
Lewis Acid ◽  
High Efficiency ◽  
Acid Catalyst ◽  
Acid Sites ◽  
Activation Mechanism ◽  
Ambient Conditions ◽  
Lewis Acid Sites ◽  
Metal Free ◽  
Nitrogen Activation ◽  
Lewis Acid Catalyst

Metal-free Lewis acid catalyst is developed as a high-efficiency electrocatalyst to enable nitrogen reduction under ambient conditions. A new nitrogen activation mechanism via the pull–pull effect between Lewis acid sites and nitrogen is also proposed.

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