Expanding the Chemical Space of Electrophilic ß-Glycosyl ß-Lactams through Photoinduced Diastereoselective Functionalization.

Herein, we present a photoinduced diastereoselective C-3 functionalization of electrophilic ß-glycosyl ß-lactams. The developed protocol is simple, mild, and scalable and explores the use of 3-exomethylene ß-lactams as reaction partners in a Giese type reaction. The key nucleophilic alkyl radical is generated by a photoinduced electron transfer process in the EDA complex formed by NHPI and Hantzsch esters. The diastereoselective hydrogen atom transfer to the ß-lactam radical intermediate enables the synthesis of various N-phenyl ß-glycosyl ß-lactams.

A copper-catalysed one-pot hydroboration/azidation/cycloaddition reaction of alkynes.

Herein we report our study on the development of a catalytic one-pot process, showing the challenges and advantages encountered all over the way. At the end, we developed a regioselective, environmentally friendly, and operationally simple method to explore the reactivity of functionalized propargylic alkynes through three copper-catalysed reactions in a single reaction vessel. The sequence consisted of a hydroboration, azidation, and 1,3-dipolar cycloaddition and led to the regioselective formation of vinyl 1,2,3-triazoles in good yields.

Synthetic Approaches to Selenoesters.

Selenoesters are compounds of great synthetic relevance since they can be used in several types of chemical transformations and mainly due to their great capacity in the formation of acyl radicals. Therefore, the scientific community has been developing several methods for the synthesis of this class of molecules. This review will address the synthesis of these compounds from different starting materials, such as carboxylic acids derivatives (acid chlorides and anhydrides), aldehydes, selenoacetylenes and miscellaneous methods.

Meyer-Schuster-type rearrangement for the synthesis of α-selanyl-α,ß-unsaturated thioesters.

A new approach to prepare α-selanyl-α,ß-unsaturated thioesters from propargylthioalkynes and an electrophilic selenium species is reported. Pivotal is the intermediacy of a sulfur-stabilized vinyl cation, which is captured intramolecularly and ultimately enables 37 examples of the target compounds to be prepared in good yields. Computational studies shed light on the nature of intermediates in this transformation.

Redox-Neutral Synthesis of Selenoesters by Oxyarylation of Selenoalkynes under Mild Conditions.

An approach for the mild synthesis of selenoesters starting from selenoalkynes through an acid-catalyzed, redox-neutral oxyarylation reaction is reported. Brønsted acid activation of a selenoalkyne leads to a selenium-stabilized vinyl cation, which is captured by an aryl sulfoxide and undergoes sigmatropic rearrangement to deliver the final α-arylated selenoester product. Computational studies have been carried out to elucidate the nature of the Se-stabilized carbocation.

Ynamide Preactivation Allows a Regio- and Stereoselective Synthesis of α,ß-Disubstituted Enamides.

A novel ynamide preactivation strategy enables the use of otherwise incompatible reagents and allows preparation of α,ß-disubstituted enamides with high regio- and stereoselectivity. Mechanistic analysis reveals the intermediacy of a triflate-bound intermediate as a solution-stable, effective keteniminium reservoir, whilst still allowing subsequent addition of organometallic reagents.