Metal-Free Oxidative Decarbonylative [3+2] Annulation of Terminal Alkynes with Tertiary Alkyl Aldehydes toward Cyclopentenes.

A new metal-free oxidative decarbonylative [3+2] annulation of terminal alkynes with tertiary alkyl aldehydes is presented, which features broad substrate scope and excellent selectivity. The selectivity of this reaction toward cyclopentenes and indenes relies on the nature of the aldehyde substrates. While treatment of tertiary γ,δ-unsaturated aldehydes with common terminal alkynes assembles cyclopentenes, 2-methyl-2-arylpropanals succeed in accessing indenes.

Rhodium-catalyzed synthesis of isoquinolines and indenes from benzylidenehydrazones and internal alkynes.

A new route is presented for the selective assembly of isoquinolines and indenes by rhodium-catalyzed tandem cyclization of benzylidenehydrazones with internal alkynes. This method involves the selective cleavage of the N-N bond and the C═N bonds and is dependent on the substituents of the benzylidenehydrazone.

Single-structure 3-axis Lorentz force magnetometer based on an AlN-on-Si MEMS resonator.

This work presents a single-structure 3-axis Lorentz force magnetometer (LFM) based on an AlN-on-Si MEMS resonator. The operation of the proposed LFM relies on the flexible manipulation of applied excitation currents in different directions and frequencies, enabling the effective actuation of two mechanical vibration modes in a single device for magnetic field measurements in three axes. Specifically, the excited out-of-plane drum-like mode at 277 kHz is used for measuring the x- and y-axis magnetic fields, while the in-plane square-extensional mode at 5.4 MHz is used for measuring the z-axis magnetic field. The different configurations of applied excitation currents ensure good cross-interference immunity among the three axes. Compared to conventional capacitive LFMs, the proposed piezoelectric LFM utilizes strong electromechanical coupling from the AlN layer, which allows it to operate at ambient pressure with a high sensitivity. To understand and analyze the measured results, a novel equivalent circuit model for the proposed LFM is also reported in this work, which serves to separate the effect of Lorentz force from the unwanted capacitive feedthrough. The demonstrated 3-axis LFM exhibits measured magnetic responsivities of 1.74 ppm/mT, 1.83 ppm/mT and 6.75 ppm/mT in the x-, y- and z-axes, respectively, which are comparable to their capacitive counterparts.

Palladium-catalyzed methylation of alkynyl C(sp)-H bonds with dimethyl sulfonium ylides.

A novel palladium-catalyzed methylation protocol for the synthesis of methyl-functionalized internal alkynes has been established. This methylation method is achieved through a C(sp)-C(sp(3)) bond formation process and represents a new synthetic application of sulfonium ylides.

Palladium-catalyzed cyclocarbonylation of arynes with methyl allyl carbonates: selective synthesis of 1H-inden-1-ones.

A selective protocol for the synthesis of 2-methylene-3-substituted-2,3-dihydro-1H-inden-1-ones and 2-benzylidene-2,3-dihydro-1H-inden-1-ones has been developed via palladium-catalyzed cyclocarbonylation reactions of arynes with allyl carbonates and carbon monooxide (CO). It is noteworthy that the selectivity of this new route is depended on both substrates and ligands.

Annulation Cascades of N-Allyl- N-((2-bromoaryl)ethynyl)amides Involving C-H Functionalization.

An annulation cascades of N-allyl- N-((2-bromoaryl)ethynyl)amides with terminal alkynes or 1,3-dicarbonyls involving C-H functionalization for producing 2,3-functionalized indoles has been first developed by means of Cu catalysis. The method is enabled by the formation of the ketenimine intermediates to deliver 2,3-disubstituted indoles through a sequence of aza-Claisen rearrangement, C-H functionalization, Ullmann C-N coupling, and cyclization.

Oxidative 1,2-carboamination of alkenes with alkyl nitriles and amines toward γ-amino alkyl nitriles.

Difunctionalization of alkenes has become a powerful tool for quickly increasing molecular complexity in synthesis. Despite significant progress in the area of alkene difunctionalization involving the incorporation of a nitrogen atom across the C-C double bonds, approaches for the direct 1,2-carboamination of alkenes to produce linear N-containing molecules are scarce and remain a formidable challenge. Here we describe a radical-mediated oxidative intermolecular 1,2-alkylamination of alkenes with alkyl nitriles and amines involving C(sp3)-H oxidative functionalization catalysed by a combination of Ag2CO3 with iron Lewis acids. This three-component alkene 1,2-alkylamination method is initiated by the C(sp3)-H oxidative radical functionalization, which enables one-step formation of two new chemical bonds, a C-C bond and a C-N bond, to selectively produce γ-amino alkyl nitriles.

Dehydrogenative [2 + 2 + 1] Heteroannulation Using a Methyl Group as a One-Carbon Unit: Access to Pyrazolo[3,4-c]quinolines.

A practical and straightforward access to pyrazolo[3,4-c]quinolines by molecular sieve mediated dehydrogenative [2 + 2 + 1] heteroannulation of N-(o-alkenylaryl)imines with aryldiazonium salts is described using a sp(3)-hybrid carbon atom as a one-carbon unit. The reaction enables the formation of three new chemical bonds, a C-C bond and two C-N bonds, in a single reaction and features simple operation and excellent functional group tolerance.

Metal-free nitrative cyclization of N-aryl imines with tert-butyl nitrite: dehydrogenative access to 3-nitroindoles.

We describe here a new metal-free route for the synthesis of 3-nitroindoles by the nitrative cyclization of N-aryl imines with tert-butyl nitrite. The radical transformation allows the assembly of the indole framework through oxidative cleavage of multi C-H bonds, a nitration, cyclization and isomerization cascade.

Silver-mediated radical cyclization: construction of Δ(2)-isoxazolines from α-halo ketoximes and 1,3-dicarbonyl compounds.

A novel route to Δ(2)-isoxazolines is presented via silver-mediated radical cyclization of α-halo ketoximes with 1,3-dicarbonyl compounds. This method is performed using a radical strategy, and represents a new example of silver-initiated generation of oxime radicals for the formation of the C(sp(3))-O bonds.

Oxidative coupling of alkenes with amides using peroxides: selective amide C(sp3)-H versus C(sp2)-H functionalization.

A new oxidative coupling of unactivated terminal alkenes with amides using peroxides is described, in which mono- and difunctionalization of alkenes are selectively achieved. In this reaction with amides, the chemoselectivity toward the functionalization of the C(sp(3))-H bonds adjacent to the nitrogen atom or the functionalization of the carbonyl C(sp(2))-H bonds across alkenes relies on the reaction conditions.