Asymmetric Defluoroallylation of 4-Trifluoromethylpyridines Enabled by Umpolung C-F Bond Activation

Carbon-fluorine bond activation reaction of the trifluoromethyl group represent an important approach to fluorine-containing molecules. While selective defluorofunctionalization reactions of CF3-containing substrates have been achieved by invoking difluorocarbocation, difluorocarboradical, or difluoroorganometallic species as the key intermedi-ate, the transformations via fluorocarbanion mechanism remained a limited success. Furthermore, the enantioselective defluorotransformation of CF3 group has not yet been realized. Herein, we report a defluorofunctionalization reaction of 4-trifluoromethylpyridines involving pyridyldifluoromethyl anion as the key intermediate, which was developed based upon our previous studies on the N-boryl pyridyl anion chemistry. When combined with Ir-catalysis, asymmetric defluoroallylation of 4-trifluoromethylpyridines could be achieved to forge a difluoroalkyl-substituted chiral center. The present work opens up a new opportunity for the defluorofunctionalization of CF3 group, and provides new insights into the N-boryl pyridyl anion chemistry.

Impact of Na/Al Ratio on the Extent of Alkali-Activation Reaction: Non-linearity and Diminishing Returns

To address the high CO2 footprint associated with cement production, many alternative, sustainable binders are now gaining worldwide attention–including alkali-activated materials. The alkali-activation reaction of metakaolin is a fairly complex process involving transformation of one amorphous reactant (precursor metakaolin) into another amorphous product or products (N-A-S-H gel and/or disordered zeolite type phases). In spite of this complexity, researchers in the past 2 decades have gained significant knowledge on the nature of this reaction at multiple scales. Understanding and developing a clear relationship between the alkalinity of the mix and the extent of reaction is of high interest for practical applications. However, detailed and thorough investigations on this important relationship are limited. Here, in this study, we address this gap by systematically investigating a series of alkali-activated materials samples with a wide range of Na/Al ratios (0.5–1.8) using seven different yet complementary analytical techniques (isothermal calorimetry, FTIR, XRD, TGA, NMR, and Raman imaging). Applied in tandem, these tools reveal a clear but non-linear relationship between the Na/Al ratio and the extent of alkali-activation reaction indicating diminishing returns at higher Na/Al ratios, where higher Na/Al ratios cause an increase in the degree of reaction until a certain point at which the increase in Na/Al ratio does not significantly affect the reaction kinetics, but may affect the gel polymerization. These findings could potentially aid decision making for commercial applications of AAMs where alkalinity of the mix is an important parameter for performance as well as safety.

A concise and efficient CuI-catalyzed synthesis of diimino dihydroquinazoline derivatives from isocyanides and guanidines derivatives through intramolecular C–H activation

: A novel series of diimino dihydroquinazoline derivatives were synthesized from isocyanides and guanidine analogs in quantitative yields by applying an efficient, inexpensive, one-pot copper-catalyzed intramolecular C-H activation reaction under mild conditions. The structures were confirmed on the basis of IR, 1HNMR, 13C NMR, mass spectral and elemental analysis data. The protocol offers advantages like short reaction time, simple workup process, high yields, and an environmentally benign methodology. Interestingly, better results (yield = 82%) were observed in terms of the yield obtained by using a mixture of CuI, Cs2CO3 and acetonitrile as the catalyst, base and solvent, respectively. The data also suggested that compound 5i is produced with the highest yield (87%) from the corresponding diisopropyl carbon diimide, 4-nitroaniline and phenyl isocyanide. Finally, a mechanistic explanation for the reaction promoted by cuprous iodide (CuI) was proposed on the basis of previous investigations and our experimental observations.

Ru(II)-Catalyzed C-H Activation Reaction between 2-Phenylquinazolinone and Vinylene Carbonate

In the report, we described the ruthenium(II)-catalyzed C-H activation/cyclization of 2-arylquinazolinones with vinyl carbonate for the synthesis of different fused quinazolinones. Through this strategy, the 6-hydroxy-5,6-dihydro-8H-isoquinolino[1,2-b]quinazolin-8-one and 8H-Isoquino[1,2-b] quinazolin-8-one have been obtained respectively under different temperatures. Additionally, the reaction features broad substrate scope and good yields, only producing carbon dioxide as byproduct. Moreover, we performed preliminary mechanistic studies of this reaction and proposed a possible mechanism.

Ruthenium Metal: Uplifting Regioselective C-H activation

: Construction of the C-C bond has always been a challenge for organic chemists, because of the reactivity of carbon atoms. The making of nucleophilic carbon started with the Grignard reagent, enolate, and the ylide, moreover, the aromatic carbon activation was the challenge before the era of organometallic chemistry. The recognition of organometallic chemistry was in the light when the Nobel Prize was given for the C-C bond in the year 2010, However, The pre functionalization of the C-H bond was an additional step with halogenated reagent, which was the limitation of this reaction. Later the C-H activation with organometals like Pd, Ru, Cu, Rh, and other transition metal came into existence, where the directing group and metal makes feasibility to form the nonreactive C-C bond. In spite of several organometals, Ru made a special place due to the reactivity, coast and, stability. Various C-H activation reaction protocols were reported with their high regioselectivity as well as high atom economy. The C-H activation protocol is now in the next level of development like SP3, SP2 ortho, meta, and para C-H activation. Here in our aim is to get the summarized information regarding the Ru and their ortho -regioselective reactions with the help of the directing group. The reader will be benefited from the mechanistic part and the concept of C-H activation with some of the important examples, which have been summarized here in with the various Ru based regioselective reactions through weak and strong coordination of metal and substrate.