B2(OH)4-Mediated Reductive Ring-Opening of N-Tosyl Aziridines by Nitroarenes: A Green and Regioselective Access to Vicinal Diamines.

The nucleophilic ring-opening of aziridine derivatives provides an important synthetic tool for the preparation of various ß-functionalized amines. Amines as nucleophiles are employed to prepare synthetically useful 1,2-diamines in the presence of various catalysts or activators. Herein, the B2(OH)4-mediated reductive ring-opening transformation of N-tosyl aziridines by nitroarenes was developed. This aqueous protocol employed nitroarenes as cheap and readily available amino sources and proceeds under external catalyst-free conditions. Control experiments and DFT calculations pointed to the in situ reduction of nitroarenes to aryl amines via N-aryl boramidic acid (E) and an SN1-type ring-opening of N-tosylaziridines by the resultant aryl amines with high regioselectivity.

A Synthesis of α-Alkyl Cycloenones by Pd-Catalyzed Suzuki-Miyaura Coupling with Cyclic Morita-Baylis-Hillman Adducts.

We herein disclose a Pd-catalyzed Suzuki-Miyaura coupling of cyclic Morita-Baylis-Hillman adducts with organoboronic acids under mild conditions, which allows for a rapid access to diverse α-alkyl substituted cycloenones. The advantage of this method resides in the employment of functionalized allyl alcohols as the unprecedented electrophilic partners in the absence of external activators.

Palladium-Catalyzed Suzuki-Miyaura Reactions with Triazenyl-Tethered Aryl Bromides: Exploiting the Orthogonal Coupling Sites under Different Conditions.

Transition-metal-catalyzed cross-coupling of arenes bearing two or more potential coupling sites is often challenging because of the chemoselectivity issue. If orthogonal cross-couplings were applicable, one can develop a synthetically useful approach for consecutive functionalization of the starting arenes compounds. We herein reported a Suzuki-Miyaura coupling of triazenyl-substituted aryl bromides catalyzed by PdCl2(PCy3)2/PPh3 under basic conditions. The resultant polyfunctionalized aryl triazenes could undergo Suzuki-Miyaura couplings under acidic conditions or be converted to many other functionalized arenes. This orthogonal coupling strategy allows for a sequential functionalization of arenes with same type of nucleophilic reagents toward the synthesis of diverse biaryls and teraryls.

Synthesis of ortho-Methylated Benzamides via Palladium-Catalyzed Denitrogenative Cross-Coupling Reaction of [1,2,3]-Benzotriazin-4(3H)-ones with DABAL-Me3.

We herein developed a palladium-catalyzed reaction of [1,2,3]-benzotriazin-4(3H)-ones with DABAL-Me3 [bis(trimethylaluminum)-1,4-diazabicyclo[2.2.2]octane adduct], a cheap, stable, and solid organoaluminum reagent. In the presence of Pd(OAc)2/XantPhos as a commercially available catalyst, [1,2,3]-benzotriazin-4(3H)-ones underwent denitrogenative coupling with DABAL-Me3 to afford a wide array of N-aryl amides derived from ortho-methylated carboxylic acids. Under the same catalytic conditions, ortho-ethylation of [1,2,3]-benzotriazin-4(3H)-ones could also be achieved by using triethylaluminum.