Oxidative Dehydrogenation of Hydrazobenzenes toward Azo Compounds Catalyzed by -Butyl Nitrite in EtOH.

We describe a -butyl nitrite-catalyzed oxidative dehydrogenation of hydrazobenzenes for producing azobenzenes. This method proceeds at ambient temperature and under an atmospheric environment by employing eco-friendly EtOH as the medium, representing a mild, general route to the synthesis of various symmetrical and nonsymmetrical azobenzenes in excellent yields with broad functional group tolerance.

One-Carbon Incorporation Using Cyclobutanone Oxime Ester Enabled [2 + 2 + 1] Carboannulation of 1,7-Enynes by C-C/N-O Bond Cleavage and C-H Functionalization.

A NiCl-promoted [2 + 2 + 1] carboannulation of 1,7-enynes with internally oxidative cyclobutanone oximes to produce canyo-functionalized 4-cyclopenta[]quinolin-4-ones is disclosed. Through C-C/N-O bond cleavage and C-H functionalization, the process enables one-carbon incorporation using cyclobutanone oximes to achieve [2 + 2 + 1] carboannulation of 1,7-enynes, which is highlighted by allowing the formation of four new bonds with high selectivity and broad substrate scope.

Metal-free oxidative [2+2+1] heteroannulation of 1,7-enynes with thiocyanates toward thieno[3,4-c]quinolin-4(5H)-ones.

A new metal-free oxidative [2+2+1] heteroannulation of 1,7-enynes with thiocyanates for producing thieno[3,4-c]quinolin-4(5H)-ones is presented. This reaction employs benzoylperoxide (BPO) as the oxidant and sodium thiocyanate as the sulfur source to enable the formation of three chemical bonds, two C-S bonds and one C-C bond, in a single reaction, and represents a new, practical access to S-heterocycles with the avoidance of the use of metal catalysts and excess bases.

Copper-Catalyzed Annulation Cascades of Alkyne-Tethered α-Bromocarbonyls with Alkynes: An Access to Heteropolycycles.

We here describe a new Cu-catalyzed annulation cascade of alkyne-tethered α-bromocarbonyls with common alkynes for the synthesis of various heteropolycycle frameworks, including 1 H-benzo[ de]quinolin-2(3 H)-ones, 4 H-dibenzo[ de,g]quinolin-5(6 H)-one, and benzo[ de]chromen-2(3 H)-one, which were constructed with high selectivity. This was achieved by two-component annulation cascades, rather than atom-transfer radical cyclization (ATRC), with alkyne-tethered α-bromocarbonyls for one-step accessing heteropolycycles via C-Br bond split, intramolecular cyclization, intermolecular [4 + 2] annulation, and aryl C(sp)-H functionalization cascades.

An access to 1,3-azasiline-fused quinolinones via oxidative heteroannulation involving silyl C(sp)-H functionalization.

A Mn-promoted intermolecular oxidative radical heteroannulation of N-(2-cyanoaryl)-acrylamides and tertiary silanes has been described, which provides an efficient route to produce silicon/nitrogen heterocycles, sila-analogues of the known carbon-based structural motifs prevalent in bioactive natural products, pharmaceuticals and materials. The reaction enables Si-incorporation by controlling accurately several chemical bond cleavage and formation processes. Moreover, this reaction represents a new one-step construction of 1,3-azasiline-fused quinolinones that was achieved via silyl C(sp)-H functionalization using an oxidative radical strategy.

Complex Annulations through Silver Carbenoid Intermediate: An Alternative Entry to Transformations of 1,2,3-Triazoles.

An alternative entry to transformations of N-sulfonyl-4-(2-(ethynyl)aryl)-1,2,3-triazoles with various generated in situ or external nucleophiles by means of silver catalysis for producing diverse functionalized isoquinolines is described. Mechanistically, the reaction is proposed to involve a key silver carbenoid intermediate, thus enabling the formation of multiple chemical bonds via ring opening, N extrusion, silver carbenoid formation, nucleophilic addition, and complex annulations cascades.