Convergent Synthesis of 1,4-Dicarbonyl Z-Alkenes through Three-Component Coupling of Alkynes, α-Diazo Sulfonium Triflate, and Water

Abstract

We report a general protocol for the convergent synthesis of 1,4-dicarbonyl Z-alkenes form alkynes using α-diazo sulfonium triflate and water. The CO, CC, and C−H bonds are formed under mild conditions with a wide range of functional groups tolerated. The reaction exhibits excellent Z-selectivity and complete regioselectivity. The resulting 1,4-dicarbonyl Z-alkenes can smoothly undergo follow-up conversion to a variety of heteroaromatic scaffolds. Moreover, the reaction also provides a facile access to the corresponding deuterated Z-alkenes and deuterated heteroarenes with a high level of deuterium incorporation (90− 97% D-inc.) by directly using D 2 O, thus rendering the method highly valuable. The comprehensive mechanistic studies indicate that a free carbyne radical intermediate is formed via the photocatalytic single electron transfer process, and KH 2 PO 4 plays a crucial role in significant improvements on yield and selectivity based on density-functional theory calculations, providing a new direction for radical coupling reactions of diazo compounds.

Generating Fischer-Type Rh-Carbenes with Rh-Carbynoids

“…In addition, we observed that sodium bicarbonate (2 equiv) slightly improved the efficiency of the reaction (entry 10) . Finally, alternative diazo compounds substituted with sulfonium, , ammonium, or bromide ( 2f – h , entries 11–13) were ineffective in promoting formation of 3a / 4a .…”

Catalytic Synthesis of Cyclopropenium Cations with Rh-Carbynoids

“…Herein, we would like to disclose the invention of a one-step Rh-catalyzed process for the preparing of CPCs that combines readily available alkynes and hypervalent iodine reagents as formal cationic carbyne sources (Figure B) . The process showed a broad scope of a new class of CPCs substituted with an ester group that, upon treatment with a diverse range of nucleophiles, provided access to valuable and elusive classes of cyclopropene derivatives …”

Photochemical synthesis of 1,2,4-triazolesviaaddition reaction of triplet intermediates to diazoalkanes and azomethine ylide intermediates

“…It is well known that incorporation of deuterium atoms into drug molecules are one the most important approaches for their activity modification. 11 To our delight, the deuterated 1,2,4-triazole 11t could be obtained in 61% yield with CD 3 CN as carbene trapping reagent. We also studied the effect of substituents on azodicarboxylates to the reaction efficiency ( Scheme 5c ).…”