Photoinduced Decarboxylative Borylation of N-Hydroxyphthalimide Esters with Hypoboric Acid.

We developed a visible-light-driven photochemical transformation in which activated primary, secondary, and tertiary alkylcarboxylic acids were converted into the corresponding boronic esters in the absence of catechol and any added photocatalyst. The procedure relies on the utilization of hypoboric acid and redox-active esters of alkylcarboxylic acids to ensure a simple and economic procedure. Quantum chemical calculations and mechanistic considerations provide deeper insights into the mechanism of photochemical borylation reactions.

Stereoselective Direct N-Trifluoropropenylation of Heterocycles with a Hypervalent Iodonium Reagent.

The availability and synthesis of fluorinated enamine derivatives such as N-(3,3,3-trifluoropropenyl)heterocycles are challenging, especially through direct functionalization of the heterocyclic scaffold. Herein, a stereoselective N-trifluoropropenylation method based on the use of a bench-stable trifluoropropenyl iodonium salt is described. This reagent enables the straightforward trifluoropropenylation of various N-heterocycles under mild reaction conditions, providing trifluoromethyl enamine type moieties with high stereoselectivity and efficiency.

Understanding and Exploitation of Neighboring Heteroatom Effect for the Mild N-Arylation of Heterocycles with Diaryliodonium Salts under Aqueous Conditions: A Theoretical and Experimental Mechanistic Study.

The mechanism of arylation of N-heterocycles with unsymmetric diaryliodonium salts is elucidated. The fast and efficient N-arylation reaction is interpreted in terms of the bifunctionality of the substrate: The consecutive actions of properly oriented Lewis base and Brønsted acid centers in sufficient proximity result in the fast and efficient N-arylation. The mechanistic picture points to a promising synthetic strategy where suitably positioned nucleophilic and acidic centers enable functionalization, and it is tested experimentally.

Transition-Metal-Free N-Arylation of Pyrazoles with Diaryliodonium Salts.

A new synthetic method was developed for the N-arylation of pyrazoles using diaryliodonium salts. The transformation does not require any transition-metal catalyst and provides the desired N-arylpyrazoles rapidly under mild reaction condition in the presence of aqueous ammonia solution as a mild base without the use of inert atmosphere. The chemoselectivity of unsymmetric diaryliodonium salts was also explored with large number of examples.

Efficient copper-catalyzed trifluoromethylation of aromatic and heteroaromatic iodides: the beneficial anchoring effect of borates.

Efficient copper-catalyzed trifluoromethylation of aromatic iodides was achieved with TMSCF3 in the presence of trimethylborate. The Lewis acid was used to anchor the in situ generated trifluoromethyl anion and suppress its rapid decomposition. Broad applicability of the new trifluoromethylating reaction was demonstrated in the functionalization of different aromatic and heteroaromatic iodides.

Evaluation of bis-triphenylphosphano-copper(I)-butyrate (C3H7COOCu(PPh3)2) as catalyst for the synthesis of 1-glycopyranosyl-4-substituted-1,2,3-triazoles.

Bis-triphenylphosphano-copper(I)-butyrate (C(3)H(7)COOCu(PPh(3))(2)) was applied for the synthesis of O-peracylated 1-glycopyranosyl-4-substituted-1,2,3-triazoles from the corresponding glycosyl azides and alkynes. This catalyst proved superior to the CuSO(4)/L-ascorbic acid system even with sterically hindered and less reactive glycosyl azides.

Highly active copper-catalysts for azide-alkyne cycloaddition.

Bis-triphenylphosphano complexes of copper(I)-carboxylates serve as efficient catalysts for azide-alkyne cycloaddition. The triazole formation takes place straightforwardly at ambient temperature providing a wide variety of products with good yields in the presence of 0.005-0.05% catalyst.