High temperature resistant ultra-short DBR Yb-doped fiber laser.

We present a distributed Bragg reflector (DBR) Yb-doped fiber laser based on a pair of type IA fiber Bragg gratings (FBGs). The high temperature resistant gratings are fabricated in high absorption hydrogen loaded Yb-doped silica fiber by use of a 244 nm argon laser and phase mask method. The DBR laser, with only 10 mm cavity length, exhibits high signal-noise ratio (SNR) of over 50 dB and can survive at 450°C in a long term with stable output power and central wavelength. Besides, the laser has a relatively low temperature sensitivity of 8.9 pm/°C, which contributes to cross-sensitization of stress and temperature.

Isocyanide-Induced Activation of Copper Sulfate: Direct Access to Functionalized Heteroarene Sulfonic Esters.

A novel and direct approach to alkyl/aryl heteroarene sulfonic esters using copper sulfate as the environmentally benign inorganic sulfonation reagent was first realized with the aid of isocyanide. A variety of heterocycles reacted to afford the corresponding sulfonic esters through C-H functionalization. In this transformation, the otherwise inert copper sulfate was unusually activated by an isocyanide and employed as the source of the sulfonic substituents in an unprecedented fashion. The findings suggest that an appropriate activator may liberate the chemical activities of some relatively inert inorganic salts for organic synthesis.

Ruthenium-catalyzed double-fold C-H tertiary alkoxycarbonylation of arenes using di-tert-butyl dicarbonate.

An efficient ruthenium-catalyzed double-fold C-H alkoxycarbonylation of arenes was developed using di-tert-butyl dicarbonate as the tertiary esterification reagent, which leads to a direct route to valuable 2,6-dicarboxylated products.

Mn(II)/O2-promoted oxidative annulation of vinyl isocyanides with boronic acids: synthesis of multi-substituted isoquinolines.

An efficient manganese(II)/O2-promoted oxidative radical cascade reaction was developed for the modular synthesis of multi-substituted isoquinolines from easily accessible vinyl isocyanides and boronic acids.

Rhodium-catalyzed regioselective C-H chlorination of 7-azaindoles using 1,2-dichloroethane.

An unexpected rhodium-catalyzed regioselective C-H chlorination of 7-azaindoles was developed using 1,2-dichloroethane (DCE) as a chlorinating agent and 7-azaindole as the directing group. This protocol provides an efficient access to ortho-chlorinated azaindoles with operational simplicity, good functional group tolerance, and a wide substrate scope.

Rhodium-catalyzed direct ortho C-N bond formation of aromatic azo compounds with azides.

An efficient rhodium-catalyzed regioselective C-N bond formation of azo compounds in good to excellent yields through C-H bond functionalization using azides as the nitrogen source was developed. Alkyl, aryl, and sulfonyl azides could be efficiently assembled in this reaction with excellent functional group tolerance.

Rhodium-catalyzed direct C-H bond cyanation of arenes with isocyanide.

An efficient rhodium-catalyzed regioselective C-H bond cyanation of arenes was developed using tert-butyl isocyanide as the cyanide source. A wide range of (hetero)aryl and cycloalkenyl nitriles could be afforded with high regioselectivity and good functional group tolerance.

Palladium-catalyzed tandem allenyl and aryl C-N bond formation: efficient access to N-functionalized multisubstituted indoles.

An efficient palladium-catalyzed synthesis of N-functionalized multisubstituted indoles from easily accessible ortho-haloarylallenes and primary amines has been developed. A wide range of electronically and structurally varied nitrogen fragments could be introduced through this tandem C-N bond-forming process by tuning the reaction conditions.

Palladium-assisted regioselective C-H cyanation of heteroarenes using isonitrile as cyanide source.

A palladium-catalyzed regioselective C-H cyanation of heteroarenes was achieved using tert-butyl isocyanide as "CN" source, which provides a new and unique strategy for the preparation of (hetero)aryl nitriles. Indoles, pyrroles, and aromatic rings could be efficiently cyanated through C-H bond activation with high regioselectivity.