Understanding the Reactivity of Acyl Anion Equivalents: The Epoxide Ring Opening Case

Preparation of Functionalized Amides Using Dicarbamoylzincs

We report a new convenient preparation of dicarbamoylzincs of type (R¹R²NCO)₂Zn by the treatment of ZnCl₂ and formamides R¹R²NCHO with LiTMP in THF (15 °C, 15 min) or by the reaction of formamides R¹R²NCHO with TMP₂Zn (25 °C, 16 h). This second method tolerates sensitive groups such as an ester, ketone or nitro function. Reaction of these dicarbamoylzincs with allylic, benzylic, aryl, alkenyl bromides, acid chlorides, aldehydes or enones provided various polyfunctional amides in 47–97 % yields. ¹³C NMR characterization of these new carbamoylzinc derivatives is reported.

One pot synthesis of isocyano-containing, densely functionalised gem-difluoroalkenes from α-trifluoromethyl alkenes, alkyl halides and TosMIC

A base-promoted one-pot, three-component reaction of TosMIC with α-trifluoromethyl alkenes and alkyl halides has been deveolped for the synthesis of isocyano-containing, densely functionalised gem-difluoroalkenes.

The Future of Retrosynthesis and Synthetic Planning: Algorithmic, Humanistic or the Interplay?

The practice of deploying and teaching retrosynthesis is on the cusp of considerable change, which in turn forces practitioners and educators to contemplate whether this impending change will advance or erode the efficiency and elegance of organic synthesis in the future. A short treatise is presented herein that covers the concept of retrosynthesis, along with exemplified methods and theories, and an attempt to comprehend the impact of artificial intelligence in an era when freely and commercially available retrosynthetic and forward synthesis planning programs are increasingly prevalent. Will the computer ever compete with human retrosynthetic design and the art of organic synthesis?

Asmic Isocyanide [3 + 2] Cascade to Dihydrooxazoles and Dihydroimidazoles

The versatile isocyanide building block Asmic, anisylsulfanylmethylisocyanide, reacts with aldehydes and ketones in a BF₃·OEt₂-mediated condensation to afford thioimidoyl-substituted 2,5-dihydrooxazoles. The condensation is distinguished from related base and transition-metal-catalyzed [3 + 2] processes in proceeding via the condensation of aldehydes and ketones with 2 equiv of an isocyanide followed by a molecular rearrangement that installs four new bonds. BF₃·OEt₂ mediates an analogous condensation of Asmic with imines to generate N-substituted dihydroimidazoles. Mechanistically, BF₃·OEt₂ activates the isocyanide to facilitate deprotonation evolving to a zwitterion that traps π-electrophiles in a formal [3 + 2] process. A second deprotonation-condensation with Asmic initiates a structural rearrangement involving a sulfanyl elimination-addition transposition sequence. The resulting dihydrooxazoles and dihydroimidazoles contain a thioimidate that serves as a diversification point for further elaboration.

Metalated isocyanides: formation, structure, and reactivity

Metalated isocyanides are highly versatile organometallics. Central to the reactivity of metalated isocyanides is the presence of two orthogonally reactive carbons, a highly nucleophilic "carbanion" inductively stabilized by a carbene-like isocyanide carbon. The two reactivities are harnessed in the attack of metalated isocyanides on π-electrophiles where an initial nucleophilic attack leads to an electron pair that cyclizes onto the terminal isocyanide carbon in a rapid route to diverse, nitrogenous heterocycles. Harnessing the potent nucleophilicity of metalated isocyanides while preventing electrophilic attack on the terminal isocyanide carbon has largely been driven by empirical heuristics. This review provides a foundational understanding by surveying the formation, structure, and properties of metalated isocyanides. The focus on the interplay between the structure and reactivity of metalated isocyanides is anticipated to facilitate the development and deployment of these exceptional nucleophiles in complex bond constructions.

Aryl Azides as Forgotten Electrophiles in the Van Leusen Reaction: A Multicomponent Transformation Affording 4-Tosyl-1-arylimidazoles

Considering aryl azides as electrophilic partners for the TosMIC mediated Van Leusen reaction, a novel multicomponent synthesis of 4-tosyl-1-arylimidazoles is reported. In this transformation, two molecules of TosMIC participate in the reaction mechanism in two different ways, with the second molecule undergoing a novel type of fragmentation resulting in the incorporation of a C-H into the final product.

Recent advances and applications of p-toluenesulfonylmethyl isocyanide (TosMIC)

TosMIC, a unique and multifunctional synthetic reagent, reacts with a wide spectrum of synthons to deliver novel scaffolds.

Pot-Economy Autooxidative Condensation of 2-Aryl-2-lithio-1,3-dithianes

The autoxidative condensation of 2-aryl-2-lithio-1,3-dithianes is here reported. Treatment of 2-aryl-1,3-dithianes with n-BuLi in the absence of any electrophile leads to condensation of three molecules of 1,3-dithianes and formation of highly functionalized α-thioether ketones orthothioesters in 51-89% yields upon air exposure. The method was further expanded to benzaldehyde dithioacetals, affording corresponding orthothioesters and α-thioether ketones in 48-97% yields. The experimental results combined with density functional theory studies support a mechanism triggered by the autoxidation of 2-aryl-2-lithio-1,3-dithianes to yield a highly reactive thioester that undergoes condensation with two other molecules of 2-aryl-2-lithio-1,3-dithiane.

Arylsulfonylmethyl isocyanides: a novel paradigm in organic synthesis

p-Tosylmethyl isocyanide (TosMIC), an α-acidic isocyanide has emerged as a privileged reagent to access biologically relevant fused heterocycles and some natural products like (−)-ushikulide A, variolin B, porphobilinogen and mansouramycin B.