A photocatalyst-free radical cleavage of α-diazo sulfonium salts has been developed for the first time. The reaction provides an efficient method for the generation of diazomethyl radicals from α-diazosulfonium triflates under photochemical conditions. Utilizing the in situ generated diazomethyl radicals as key intermediate, the coupling cyclization reaction of α-diazosulfonium triflates with α-oxocarboxylic acids or alkynes has been achieved. The method affords a diverse set of important 2,5-disubstituted 1,3,4-oxadiazoles and 3,5-disubstituted-1H-pyrazoles with excellent regioselectivity in a single step. A reaction mechanism involving a radical pathway was further supported by control experiments and DFT calculations.

A rhodium-catalyzed coupling cyclization of isocyanides with 2-azidophenyloxyacrylates has been developed for the first time. This reaction allows divergent syntheses of two significant N-heterocycles, five-membered N-(3-substituted benzo[d]oxazol-2(3H)-ylidene)amines and dihydrobenzo[d]oxazoles, from...

A NaN­(SiMe3)2/CsTFA copromoted aminobenzylation/cyclization reaction of 2-isocyanobenzaldehydes with toluene derivatives or benzyl compounds has been developed. The reaction works with a broad range of toluene derivatives and benzyl compounds, and provides a simple and efficient strategy for the synthesis of 4-benzyl-substitued dihydroquinazoline and quinazoline derivatives from easily available acyclic starting materials in a single step. Further applications, including synthesis of quinazoline, dihydroindolo­[1,2-c]­quinazoline, and dihydro-8H-isoquinolino­[2,3-c]­quinazoline, demonstrated the tremendous potential of the tandem reaction.

A Lewis acid mediated conjugate addition of isocyanides to β-hydroxy-α-diazo carbonyls has been developed for the first time. The reaction realizes the efficient construction of quaternary carbon centers and provides a novel and efficient strategy for the synthesis of β-carboxamido-α-diazo carbonyls that would be otherwise difficult to form in a single step. Further applications, including synthesis of methylenecyclohexane, spiro-β-lactam, and nitrogen-bridged tricyclic β-lactam, demonstrated the tremendous potential of the coupling reaction.

A novel DBU-promoted tandem cyclization reaction of ynones with diazo compounds as the N-terminal electrophiles has been developed. The reaction provides a simple and efficient method for the synthesis of fused eight-membered oxocino[2,3-c] pyrazoles from readily available acyclic starting materials in a single step. This reaction allows the formation of four new bonds and two rings in a highly regio-and diastereoselective manner, where two adjacent stereocenters are created simultaneously in an atomeconomic manner.E ight-membered cyclic ethers are privileged structural motifs found in a wide variety of natural products and drug molecules (Figure 1). 1 These compounds possess diverse pharmacological and biological properties as well as structural complexity and have attracted considerable attention of organic and medicinal chemists. 2 In comparison with five-to seven-membered rings, construction of eight-membered rings from acyclic precursors is often associated with constructive challenges owing to unfavorable enthalpic and entropic barriers in transition states. 3 In spite of the obstacles, a number of useful methods toward these scaffolds, such as ring-closing metathesis, 4 ring expansions, 5 retro-Claisen rearrangement, 6 intramolecular alkylation, 7 and others, 8 have been developed. However, these methods suffer from limited substrate scope, costly catalysts, unsatisfactory yields, multistep synthesis, and poor stereoselectivities. In addition, as important members of these families, aromatic ring-fused eight-membered cyclic ethers could possess important potential biological and Letter pubs.acs.org/OrgLett