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Cleavage of C(CO)–C bonds is a fascinating transformation that offers exciting opportunities for development of new synthetic methodologies through reconstruction of the molecular skeleton. However, the catalytic insertion of heteroallenes into C(CO)–C bonds of unstrained 1,3-diketones is so far challenging and still unknown. Herein, we report an environmentally friendly and green synthetic approach to prepare racemic or enantioenriched 3,4,6-trisubstituted α-pyrones through the cheap K2CO3-catalyzed formal C(CO)–C bond insertion reaction of ketenimines with 1,3-diketones. In addition, a one-pot procedure leading to either 3,4,6-trisubstituted α-pyrones or 4,6-disubstituted α-pyrones through an unprecedented sequential Pd(0) or Co(II)/K2CO3 catalysis has also been developed. The synthetic utility of this methodology was demonstrated by the broad substrate scope, the concise synthesis of analogues of pharmaceutically active compounds, and the diverse derivatization of the pyrone framework. More importantly, this work not only opens up a new avenue for designing structurally non-traditional α-pyrones, but also unlocks the huge potential of some extended π-conjugated α-pyrones with optoelectronic application in organic light-emitting diodes. [ABSTRACT FROM AUTHOR]

This study aims to investigate the heat and thermal insulation mechanisms of aerogel heat-insulating reflective coatings. Two working conditions, the hot box method and the open environment at the hot end, were simulated using a gypsum board as the substrate. We conducted thermal tests on blank panels, composite panels with aerogel heat-insulating reflective coatings, and XPS-insulated composite panels for two operating conditions. And the thermal insulation power calculation was carried out for the reflective and barrier materials. The test results show that the air temperature differences between the hot and cold ends of the blank, aerogel coating, and XPS boards under the hot box method were 28.8 °C, 38.2 °C, and 55.2 °C, respectively, and that the air temperature differences between the cold ends of the coating and XPS panels under the natural environment heating condition were 24.2 °C and 24 °C, respectively. Theoretical calculations show that the aerogel heat-insulating reflective coatings produce a net radiative cooling power of 145.9 W/m² when the surface of the specimen is at the same temperature as the ambient temperature. The heat flux powers of the aerogel coating board and XPS panel were 9.55 W/m² and 1.65 W/m² when the temperature difference between the two surfaces on both sides of the specimen was 10 °C, respectively. [ABSTRACT FROM AUTHOR]

Catalytic tandem cyclization of ynamides has attracted considerable interest in organic synthesis because of its atom economy in the rapid formation of polycyclic compounds. However, examples on the construction of pentacyclic spiroindolines are quite scarce. Herein, we described a BiCl3‐mediated tandem cyclization reaction of tryptamine‐ynamides, which led to the formation of appealing pentacyclic spiroindoline scaffolds in moderate to excellent yields. In addition, such a reaction can lead to the divergent synthesis of tricyclic indole derivatives with moderate yields by engineering substrate structures. The synthetic utility of this methodology has also been demonstrated by further interesting transformations. [ABSTRACT FROM AUTHOR]

Herein a catalyst‐free solvent‐controlled method for the divergent synthesis of spirocyclopropyl and spiropyrazoline oxindoles from 3‐ylideneoxindoles and ethyl diazoacetate was developed. With ClCH2CH2Cl as the solvent, spirocyclopropyl oxindoles were obtained in moderate to excellent yields, whereas the use of MeOH as solvent afforded spiropyrazoline oxindoles in moderate to good yields. The readily available substrates, simple operation and various product transformations further highlighted the utility of this method. [ABSTRACT FROM AUTHOR]

The base-mediated allylic defluorinative functionalization of β-CF 2 H-1,3-enynes with nucleophiles is described, affording terminal monofluoroalkenes bearing an alkynyl group in synthetically useful yields and Z / E selectivities. Importantly, the resultant Z / E mixture could be separated by flash chromatography in all cases; thus, stereoisomerically pure monofluoroenynes were obtained. Postsynthetic modifications of the synthesized monofluoroenynes were also accomplished to access diverse molecular structures. Computational studies disclosed the origin of the diastereoselectivity.

A 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed cascade annulation reaction between p -quinamines and 3-formylchromones was developed, affording a series of benzopyrone-fused hydrobenzo[ c , d ]indoles in moderate to high yields with excellent diastereoselectivity. This cascade reaction is efficient since two new rings as well as one C-N, one C═C, and two C-C bonds are created in a single step. The scale-up synthesis and versatile transformations of the products further demonstrated the practicality and utility of this approach.

A base-controlled divergent cyclization between 2-mercaptobenzimidazoles and β-CF 3 -1,3-enynes providing either trifluoromethylated or fluorinated benzo[4,5]imidazo[2,1- b ][1,3]thiazines has been developed. The β-CF 3 -1,3-enyne, as a three-carbon synthon, underwent a 1,8-diazabicyclo[5.4.0] undec-7-ene (DBU)-catalyzed tandem hydroamination/intramolecular hydrothiolation to give CF 3 -substituted 3,4-dihydro-2 H -benzo[4,5]imidazo[2,1- b ][1,3]thiazine, whereas reaction with KOH afforded fluorinated 4 H -benzo[4,5]imidazo[2,1- b ][1,3]thiazine exclusively. In addition, the synthetic utility of this methodology was showcased through a variety of downstream derivatizations.

A new class of Michael acceptor, tetrazolyl-trifluoromethyl alkenes, has been discovered. They readily undergo Michael-type addition instead of addition-elimination reaction with aliphatic amines and azoles to furnish β-trifluoromethyl alkylamines and CF 3 -substituted 1,2-bisazole derivatives, respectively. Additionally, some of the products are capable of engaging in microwave-assisted intramolecular denitrogenative annulation, leading to the formation of CF 3 -substituted 1,4,5,6-tetrahydro-1,2,4-triazines that are otherwise difficult to access by other methodologies.