Synthesis of vinyl-substituted alcohols using acetylene as a C2 building block

Modular and Diverse Synthesis of Acrylamides by Palladium-Catalyzed Hydroaminocarbonylation of Acetylene

The development of all kinds of covalent drugs had a major impact on the improvement of the human health system. Covalent binding to target proteins is achieved by so-called electrophilic warheads, which are incorporated in the respective drug molecule. In the last decade, specifically acrylamides emerged as attractive warheads in covalent drug design. Herein, a straightforward palladium-catalyzed hydroaminocarbonylation of acetylene has been developed, allowing a modular and diverse synthesis of bio-active acrylamides. This general protocol features high atom efficiency, wide functional group compatibility, high chemoselectivity and proceeds additive free under mild reaction conditions. The synthetic utility of this protocol is showcased in the synthesis of ibrutinib, osimertinib, and other bio-active compound derivatives.

Enantioselective Allylboration of Acetylene: A Versatile Tool for the Stereodivergent Synthesis of Natural Products

Efficient catalytic methods that allow the use of simple and abundant chemical feedstocks for the preparation of synthetically versatile compounds are central to modern synthetic chemistry. Acetylene is a basic feedstock with a remarkable production over one million tons per year, although it is underutilized in the stereoselective synthesis of fine chemicals. Here we report a facile catalytic multicomponent reaction that allows for the enantio- and diastereoselective allylboration of acetylene gas. This process is catalyzed by a chiral copper catalyst, operates without specialized equipment or pressurization, and provides chiral skipped dienes bearing stereodefined and orthogonally functionalized olefins with excellent levels of chemo-, regio-, enantio- and diastereoselectivity. The combined stereochemical features and orthogonal functionalization make the products privileged structural scaffolds to access the complete set of stereoisomers of the chiral skipped diene core through simple enantio- and diastereodivergent pathways. The utility of the method is demonstrated with the enantioselective synthesis of three bioactive natural skipped diene products, namely (+)-Nyasol, (+)-Hinokiresinol and Phorbasin C, and other related synthetically relevant chiral molecules.

Three-Component Gold(I)-Catalyzed Alkoxyvinylation

Acetylene has been underexploited despite being a highly valuable feedstock for chemical synthesis. We have developed the first true gold(I)-catalyzed intermolecular three-component reaction between acetylene, alkenes, and alcohols to afford β-vinyl hemiaminal scaffolds from N-vinyl amides. Unusual biscyclopropyl and 3-vinyl N-heterocyclic scaffolds were obtained through the incorporation of a second N-vinyl unit or tethered alkene into the starting material.

Construction of 3-Methyl-2-Substituted Benzo[b]furans and 3-Methyl-2-Substituted Benzo[b]thiophenes Using Solid Calcium Carbide as a Substitute for Gaseous Acetylene

A concise method for the facile construction of 3-methyl-2-substituted benzo[b]furans and 3-methyl-2-substituted benzo[b]thiophenes using low-cost, abundant, and easy-to-use solid calcium carbide instead of flammable and explosive gaseous acetylene as an original alkyne source, o-bromophenyl ethers or o-bromophenyl thioethers as substrates through an intramolecular carbanion-yne cyclization in a 5-exo-dig manner, and subsequent double-bond isomerization is described. The simultaneous formation of two C-C bonds is realized in a one-step route. The wide substrate scope, high yield, and simple workup manipulations are also merits of this method. The synthetic strategy can also be suitable for the gram scale.

Ligand Control of Copper-Mediated Cycloadditions of Acetylene to Azides: Chemo- and Regio-Selective Formation of Deutero- and Iodo-Substituted 1,2,3-Triazoles

The participation of σ-monocopper and σ-bis-copper acetylide in mechanistic pathways for copper-catalyzed cycloaddition (CuAAC) reactions of acetylene with azides was probed by analysis of deuterium distributions in the 1,2,3-triazole product formed by deuterolysis of initially formed mono- and bis-copper triazoles. The results show that, when Cu(Phen)(PPh3)2NO3 is used as the catalyst for reactions of acetylene with azides in DMF/D2O, 1-substituted-5-deutero-1,2,3-triazoles are generated selectively. This finding demonstrates that the Cu(Phen)(PPh3)2NO3-catalyzed cycloadditions utilize monocopper acetylide as the substrate and produce 5-copper-1,2,3-triazoles initially. Conversely, when DBU or Et3N is the copper ligand, the process takes place through initial formation and cycloaddition of bis-copper acetylide to produce 4,5-bis-copper-triazole, which reacts with D2O to form the corresponding 4,5-bis-deutero-triazole. Moreover, when C2D2 is used as the substrate, Cu(Phen)(PPh3)2NO3 as the Cu ligand, and H2O/DMF as the solvent, mono-C4-deutreo 1,2,3-triazoles are generated in high yields and excellent levels of regioselectivity. Lastly, CuAAC reactions of acetylene with azides, promoted by CuCl2·2H2O and NaI, yield 4,5-diiodo-1,2,3-triazoles with moderate to high efficiencies.

1,2,4-Triazines and Calcium Carbide in the Catalyst-Free Synthesis of 2,3,6-Trisubstituted Pyridines and Their D-, 13 C-, and Doubly D2 -13 C2 -Labeled Analogues

A novel synthetic approach to 2,3,6-trisubstituted pyridines, their 4,5-dideuterated derivatives, 4,5-13 C2 - and doubly-labeled D2 -13 C2 -pyridines has been developed using catalyst-free [4+2] cycloaddition of 1,2,4-triazines and in situ generated acetylene or labeled acetylene. Calcium carbide and water or deuterium oxide were used for the in situ generation of acetylene and dideuteroacetylene. Calcium carbide-13 C2 in the mixture with water or deuterium oxide was applied as 13 C2 -acetylene and D2 -13 C2 -acetylene source.

Gold(I)-Catalyzed Intermolecular Aryloxyvinylation with Acetylene Gas

Acetylene gas is an important feedstock for chemical production, although it is underutilized in organic synthesis. We have developed an intermolecular gold(I)-catalyzed alkyne/alkene reaction of o-allylphenols with acetylene gas that gives rise to chromanes by a stereospecific aryloxycyclization through the nucleophilic regioselective opening of cyclopropyl gold(I)-carbene intermediates. The synthetic application of this method was demonstrated in the late-stage functionalization of the natural product lapachol.

Synthesis of E-Dienyl Esters Using Acetylene as C2 Synthon

The stereoselective synthesis of dienyl esters with high atom- and step-economy has been largely unexplored. Herein, we report an efficient approach for the synthesis of E-dienyl esters via rhodium catalysis using carboxylic acid and acetylene as C2 synthon through the cascade of cyclometalation and C-O coupling. This protocol features mild conditions, excellent functional group tolerance, and exclusive E-stereoselectivity and utility in the late-stage modification of pharmaceuticals and natural products.