Gorlos-Phos: addressing the stereoselectivity in palladium-catalyzed exo-mode cyclization of allenes with a nucleophilic functionality

Copper-catalyzed remote double functionalization of allenynes

Addition reactions of molecules with conjugated or non-conjugated multiple unsaturated C-C bonds are very attractive yet challenging due to the versatile issues of chemo-, regio-, and stereo-selectivities. Especially for the readily available conjugated allenyne compounds, the reactivities have not been explored. The first example of copper-catalyzed 2,5-hydrofunctionalization and 2,5-difunctionalization of allenynes, which provides a facile access to versatile conjugated vinylic allenes with a C-B or C-Si bond, has been developed. This mild protocol has a broad substrate scope tolerating many synthetically useful functional groups. Due to the highly functionalized nature of the products, they have been demonstrated as platform molecules for the efficient syntheses of monocyclic products including poly-substituted benzenes, bicyclic compounds, and highly functionalized allene molecules.

Advances in Palladium-Catalyzed Carboxylation Reactions

In this short review, we highlight the advancements in the field of palladium-catalyzed carbon dioxide utilization for the synthesis of high value added organic molecules. The review is structured on the basis of the kind of substrate undergoing the Pd-catalyzed carboxylation process. Accordingly, after the introductory section, the main sections of the review will illustrate Pd-catalyzed carboxylation of olefinic substrates, acetylenic substrates, and other substrates (aryl halides and triflates).

Three-Component Borylallenylation of Alkynes: Access to Densely Boryl-Substituted Ene-allenes

Ene-allenes serve as versatile building blocks in organic synthesis, and the development of their efficient preparation is valuable. Herein the synthesis of boryl-substituted ene-allenes utilizing a Cu/Pd-catalyzed borylallenylation of alkynes with propargylic carbonates and bis(pinacolato)diboron is reported. Densely (tetra-, penta-, and hexa-) substituted ene-allenes were synthesized in acceptable yield with high regio- and stereoselectivity. More important molecule structures can be obtained by subsequent modifications.

Synthesis of Oxazolidin-2-ones from Unsaturated Amines with CO2 by Using Homogeneous Catalysis

Carbon dioxide (CO₂ ), a well-known greenhouse gas, is also a nontoxic, readily accessible, and renewable one-carbon (C1) source. However, owing to its thermodynamic stability and kinetic inertness, the efficient utilization of CO₂ is challenging. Much effort has been devoted to achieving efficient and selective organic transformations of CO₂ . Recently, the synthesis of important oxazolidin-2-ones from unsaturated amines by using CO₂ has attracted much attention and been heavily studied. This Focus Review presents recent advances in this area by using homogenous catalysis. The cyclization of amines that contain alkynes, alkenes, and allenes with CO₂ is discussed, and possible reaction mechanisms and applications of these transformations are also described.

Upgrading carbon dioxide by incorporation into heterocycles

Carbon dioxide is commonly regarded as the primary greenhouse gas, but from a synthetic standpoint can be utilized as an alternative and sustainable C1 synthon in organic synthesis rather than a waste. This results in the production of organic carbonates, carboxylic acids, and derivatives. Recently, CO2 has emerged as an appealing tool for heterocycle synthesis under mild conditions without using stoichiometric amounts of organometallic reducing reagents. This Minireview summarizes recent advances on methodologies for CO2 incorporation into N-, O-, and C-nucleophiles to provide various heterocycles, including cyclic carbamates, benzoxazine-2-one, 4-hydroxyquinolin-2-one, quinazoline-2,4(1 H,3 H)-diones, benzimidazolones, α-alkylidene cyclic carbonate.

Palladium-catalyzed cyclization reactions of allenes in the presence of unsaturated carbon-carbon bonds

Modern synthetic chemists have looked for rapid and efficient ways to construct complex molecules while minimizing synthetic manipulation and maximizing atom-economy. Over the last few decades, researchers have made considerable progress toward these goals by taking full advantage of transition metal catalysis and the diverse reactivities of allenes, functional groups which include two cumulative carbon-carbon double bonds. This Account describes our efforts toward the development of Pd-catalyzed cyclization reactions of allenes in the presence of compounds that contain unsaturated carbon-carbon bonds such as alkenyl halides, simple alkenes, allenes, electron-deficient alkynes, or propargylic carbonates. First, we discuss the coupling-cyclization reactions of allenes bearing a nucleophilic functionality in the presence of alkenyl halides, simple alkenes, functionalized and nonfunctionalized allenes, or electron-deficient alkynes. These processes generally involve a Pd(II)-catalyzed sequence: cyclic nucleopalladation, insertion or nucleopalladation, and β-elimination, reductive elimination, cyclic allylation or protonation. We then focus on Pd(0)-catalyzed cyclization reactions of allenes in the presence of propargylic carbonates. In these transformations, oxidative addition of propargylic carbonates with Pd(0) affords allenylpalladium(II) species, which then react with allenes via insertion or nucleopalladation. These transformations provide easy access to a variety of synthetically versatile monocyclic, dumbbell-type bicyclic, and fused multicyclic compounds. We have also prepared a series of highly enantioenriched products using an axial-to-central chirality transfer strategy. A range of allenes are now readily available, including optically active ones with central and/or axial chirality. Expansion of these reactions to include other types of functionalized allenes, such as allenyl thiols, allenyl hydroxyl amines, and other structures with differing steric and electronic character, could allow access to cyclic skeletons that previously were difficult to prepare. We anticipate that other studies will continue to explore this promising area of synthetic organic chemistry.

Palladium-catalysed inter- and intramolecular formation of C–O bonds from allenes

This review highlights the Pd-catalysed formation of a C–O bond from allenes via the inter- or intramolecular reaction.