Green Synthesis and Catalysis最新文献

A catalyst-free and atom-economical [4 ​+ ​3] cycloaddition of azadienes with C,N-cyclic azomethine imines has been developed, providing an efficient and environmentally benign access to 1,2,4-triazepines with high diastereoselectivities and yields. This reaction can be performed in 2-methyltetrahydrofuran under mild conditions smoothly.

A novel, efficient and pragmatic method to prepare gem-diboron products with vicinal tertiary/quaternary stereocenters using LiTMP-mediated 1,6-conjugate addition of gem-diborylalkanes to para-quinone methides was described for the first time. The results showed that various gem-diboron products with vicinal tertiary and quaternary stereocenters could be formed within 15 ​min at ambient temperature. This simple protocol has also been applied for the efficient synthesis of the analogue of Bedaquiline.

An acetic acid-promoted C(sp³)-H functionalization of 2-methyl quinoline, enaminoesters and elemental sulfur for the synthesis of 3,4,5-trisubstituted isothiazoles under metal-free conditions has been developed. This approach provides viable access to various 5-(quinolin-2-yl)isothiazoles in moderate to good yields with good functional group tolerance. Moreover, the success of the gram-scale reaction gives this reaction a great potential application.

A novel defluorinative ring-opening of gem-difluorocyclopropenes is presented, providing a concise and efficient method for accessing 2-fluoropropenals and 2-fluorobuta-1,3-dienes in moderate to good yields with excellent regio- and stereoselectivities. The reaction is performed under mild conditions with no need of using an excess amount of nucleophilic reagents. Water plays a crucial role in this transformation.

A visible-light-promoted formal [2 ​+ ​2 + 1] cyclization of N-aryl glycines with quinoxalin-2(1H)-ones to synthesize tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones have been developed. The protocol features operational simplicity, mild reaction conditions with blue LED light employing Ru(bpy)₃Cl₂^.6H₂O as a photoredox catalyst, a combination of O₂ from air and Cu(OAc)₂ as the oxidant and broad substrate applicability.

The efficient synthesis of useful primary amines via reductive amination of biomass-based aldehydes and ketones over earth-abundant base metal catalysts is an attractive biomass value-adding technology yet facing lots of challenges. Herein, natural attapulgite (ATP) was applied as support for the fabrication of active Ni catalysts with different Ni loadings (5–30 ​wt%) by the deposition-precipitation method. The Ni/ATP-550 catalyst with 10–15 ​wt% Ni loadings was found to present the highest catalytic performance for the synthesis of valuable 5-amino-1-pentanol (5-AP) via reductive amination of biofurfural-derived 2-hydroxytetrahydropyran among a variety of commonly used oxide supports loaded Ni catalysts, as well as ATP supported nickel catalysts with other loadings, achieving 5-AP yield up to 94%. The intrinsic activity of the Ni/ATP catalysts was found to depend strongly on the Ni⁰ crystallite size and Ni⁰ fraction of the catalysts, which generally increased with increasing Ni⁰ crystallite size and fraction, owing probably to the hydrogenation of imine intermediate is a structure-sensitive reaction. The efficient 10Ni/ATP-550 catalyst also exhibited good activity and stability in the reductive amination of several other biomass-derived aldehydes and ketones to their corresponding primary amines with good to excellent yields (81%–99%). This work provided a clean and efficient natural ATP-supported non-noble metal nickel-based catalytic system for the reductive amination of aldehydes and ketones to synthesize high-value-added primary amines, which could be a promising candidate for the industrial production of amines.