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A new approach for the synthesis of 9-membered N,N,O-heterocycles by Pd-catalyzed [6+3] dipolar cycloaddition of N-iminoisoquinolinium ylides and 2-vinyl oxetanes has been developed.

An efficient cascade approach for the construction of nitrogen-containing polycyclic compounds from amines tethered with an alkenyl (or alkynyl) group and divinyl carbonates is described.

We have developed a catalytic asymmetric allylic substitution/isomerization process with central chirality transposition. This process takes advantage of the ambident reactivity of the 2-indole imine methide generated

B(C

Despite remarkable recent advances in transition-metal-catalyzed C(sp3)−C cross-coupling reactions, there remain challenging bond formations. One class of such reactions include the formation of tertiary-C(sp3)−C bonds, presumably due to unfavorable steric interactions and competing isomerizations of tertiary alkyl metal intermediates. Reported herein is a Ni-catalyzed migratory 3,3-difluoroallylation of unactivated alkyl bromides at remote tertiary centers. This approach enables the facile construction of otherwise difficult to prepare all-carbon quaternary centers. Key to the success of this transformation is an unusual remote functionalization via chain walking to the most sterically hindered tertiary C(sp3) center of the substrate. Preliminary mechanistic and radical trapping studies with primary alkyl bromides suggest a unique mode of tertiary C-radical generation through chain-walking followed by Ni–C bond homolysis. This strategy is complementary to the existing coupling protocols with tert-alkyl organometallic or -alkyl halide reagents, and it enables the expedient formation of quaternary centers from easily available starting materials., Formation of tertiary C(sp3)-C bonds is a formidable challenge due to steric interactions and low barriers for isomerization of intermediates. Here, the authors show a Ni-catalyzed migratory 3,3-difluoroallylation of unactivated alkyl bromides at remote tertiary carbon centers.

Active millimeter wave (AMMW) imaging technique plays an important role in the security check, due to its ability to detect the concealed objects harmlessly without violating privacy. With the rapid development of deep learning, several algorithms have achieved great success in concealed object detection for AMMW images. However, their performance is restricted for the lack of sufficient data, which is the prerequisite for training the deep learning neural network. To address this task, an improved ray tracing (RT) method is proposed to fast solve scattering fields. Specifically, the Blinn-Phong model, which is a simple but effective model in computer graphics rendering, is utilized to simulate the scattering in the target surface. Comparing with the conventional full-wave simulation methods, the proposed method can achieve similar results with much less time. Then the range migration algorithm (RMA) is employed to reconstruct the images. Both visual and numerical results, as well as comparisons with other classical simulation methods, demonstrate the effectiveness and superiority of the proposed improved ray tracing framework in generating AMMW images for deep learning based concealed object detection.

A strategically novel single C–F bond functionalization of CF3-derived molecules, which shows a prominent advantage for the expedient construction of difluoromethylene-bridged organic scaffolds, is disclosed. The reported protocol consists of SN2′ amination, N-alkylation and palladium-catalyzed allylic substitution reactions, which enables straightforward arylation and alkenylation of vinyltrifluoromethane derivatives. Furthermore, this strategy is characterized by its broad substrate scope with respect to both CF3-alkene and arylboronic acid derivatives.

Herein, we report the first example of group transfer radical addition of O-vinylhydroxylamine derivatives onto unactivated alkenes. By utilizing O-vinylhydroxylamine derivatives as both the N- and C-donors, this reaction enables intermolecular carboamination of unactivated alkenes in an atom economical fashion. As the process is initiated through N-radical addition followed by C-transfer, linear carboamination products are afforded. This differs from canonical radical carbofunctionalization of olefins, which typically favors branched product owing to initiation by C-radical addition.

The trifluoroacetic acid (TFA) mediated hydration of ynamides was developed, which is an efficient approach for the synthesis of N-monosubstituted amides. This convenient method is effective with a wide range of substrates under room temperature condition, and the products are obtained in high to excellent yields through an easy work-up process.

A highly regio- and stereoselective trans-iodofluorination reaction of ynamides with NIS and Et3N·3HF has been achieved, affording (E)-α-fluoro-β-iodoenamides in moderate to good yields. The reaction proceeds under mild reaction conditions and exhibits good functional group compatibility.

An attractive and novel methodology involving Pd/Cu-catalyzed tandem head-to-tail dimerization/cycloisomerization of terminal ynamides for the synthesis of 3,5-disubstituted oxazolones was developed. Under Pd(PPh3)2Cl2/CuI cooperative catalyzed reaction conditions, it provided efficient access to 5-vinyloxazolones with exceptional functional group tolerance and good chemoselectivity. The control experiments demonstrated that Pd(PPh3)2Cl2 serves a key role in the dimerization of terminal ynamides and shows low catalytic activity in the intramolecular cyclization. Moreover, the hetero-Diels-Alder reaction of product 5-vinyloxazolones was also described, which provided polycyclic oxazolones in good yield.

A novel chalcogen-mediated oxyfunctionalization mode of ynamides for the synthesis of α-chalcogenyl acrylamides has been developed. Independent of metal catalysts, external oxidants and additives, this mild process afforded a range of structurally diverse α-chalcogenyl acrylamides, including α-selanyl acrylamides and α-tellanyl acrylamides. Interestingly, diverse ynamides tolerated in this approach gave different stereoselectivities.

The trifluoroacetic acid (TFA) mediated hydration of ynamides was developed, which is an efficient approach for the synthesis of N-monosubstituted amides. This convenient method is effective with a wide range of substrates under room temperature condition, and the products are obtained in high to excellent yields through an easy work-up process.

A mild and efficient methodology involving the I2/TBHP-mediated intermolecular iodoamination of ynamides with amines for the synthesis of α-amino-β,β-diiodo-enamides was developed. This reaction provides the first intermolecular iodoamination of terminal alkynes to diiodo-enamines and can be easily applied to a wide range of substrates.

A novel chalcogen-mediated oxyfunctionalization mode of ynamides for the synthesis of α-chalcogenyl acrylamides has been developed. Independent of metal catalysts, external oxidants and additives, this mild process afforded a range of structurally diverse α-chalcogenyl acrylamides, including α-selanyl acrylamides and α-tellanyl acrylamides. Interestingly, diverse ynamides tolerated in this approach gave different stereoselectivities.

A mild and efficient methodology involving the I2/TBHP-mediated intermolecular iodoamination of ynamides with amines for the synthesis of α-amino-β,β-diiodo-enamides was developed. This reaction provides the first intermolecular iodoamination of terminal alkynes to diiodo-enamines and can be easily applied to a wide range of substrates.