Alkenyl Triflates Research Articles

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source.

Carbon dioxide (CO2) is one of the most important materials as renewable chemical feedstock. In this review, the Co- and Rh-catalyzed transformation of CO2 via carbon–carbon bond-forming reactions is summarized. Combinations of metals (cobalt or rhodium), substrates, and reducing agents realize efficient carboxylation reactions using CO2. The carboxylation of propargyl acetates and alkenyl triflates using cobalt complexes as well as the cobalt-catalyzed reductive carboxylation of α,β-unsaturated nitriles and carboxyamides in the presence of Et2Zn proceed. A Co complex has been demonstrated to act as an efficient catalyst in the carboxylation of allylic C(sp3)–H bonds. Employing zinc as the reductant, carboxyzincation and the four-component coupling reaction between alkyne, acrylates, CO2, and zinc occur efficiently. Rh complexes also catalyze the carboxylation of arylboronic esters, C(sp2)–H carboxylation of aromatic compounds, and hydrocarboxylation of styrene derivatives. The Rh-catalyzed [2 + 2 + 2] cycloaddition of diynes and CO2 proceeds to afford pyrones.

A one-pot protocol for copper-mediated azide–alkyne cycloaddition using alkenyl triflate precursors

On the basis of the mild transformation of alkenyl triflates into alkynes promoted by LiCl, a one-pot protocol using alkenyl triflate precursors was developed for copper-mediated azide–alkyne cycloaddition. This protocol may provide an opportunity of sequentially click reactions for the construction of bifunctional probes in chemical biology studies.

Synthesis of 2-trifluoromethyl-2-hydroxy-2H-chromenes via cyclization of (Z)-trifluoromethyl alkenyl triflates and salicylaldehydes

A new and efficient method for the synthesis of 2-trifluoromethyl-2-hydroxy-2H-chromenes was developed via intermolecular cyclization of (Z)-trifluoromethyl alkenyl triflates and salicylaldehydes. A series of 2-trifluoromethyl-2-hydroxy-2H-chromenes with aryl or alkyl groups at 3-position have been obtained in moderate to excellent yields. And a key intermediate, 3-phenyl-4-(pyrrolidin-1-yl)-2-(trifluoromethyl)chroman-2-ol (6), was isolated and fully characterized, which suggests that the elimination of pyrrolidine from this intermediate is the last step during the formation of 2-trifluoromethyl-2-hydroxy-2H-chromenes.

Formation of Chiral Allylic Ethers via an Enantioselective Palladium-Catalyzed Alkenylation of Acyclic Enol Ethers.

This report details a palladium-catalyzed process to access highly functionalized, optically active allylic aryl ethers. A number of electron-deficient alkenyl triflates underwent enantioselective and site-selective coupling with acyclic aryl enol ethers in the presence of a chiral palladium catalyst. This transform provides chiral allylic ether products in high yields and excellent enantiomeric ratios, furnishing a unique disconnection to incorporate heteroatoms at a stereocenter. Finally, the applicability of the products to target synthesis was demonstrated through the formation of a chiral allylic alcohol and the generation of a flavone-inspired product.

Barbier-Negishi Coupling of Secondary Alkyl Bromides with Aryl and Alkenyl Triflates and Nonaflates.

A mild and practical Barbier-Negishi coupling of secondary alkyl bromides with aryl and alkenyl triflates and nonaflates has been developed. This challenging reaction was enabled by the use of a very bulky imidazole-based phosphine ligand, which resulted in good yields as well as good chemo- and site selectivities for a broad range of substrates at room temperature and under non-aqueous conditions. This reaction was extended to primary alkyl bromides by using an analogous pyrazole-based ligand.

Barbier–Negishi Coupling of Secondary Alkyl Bromides with Aryl and Alkenyl Triflates and Nonaflates

AbstractA mild and practical Barbier–Negishi coupling of secondary alkyl bromides with aryl and alkenyl triflates and nonaflates has been developed. This challenging reaction was enabled by the use of a very bulky imidazole‐based phosphine ligand, which resulted in good yields as well as good chemo‐ and site selectivities for a broad range of substrates at room temperature and under non‐aqueous conditions. This reaction was extended to primary alkyl bromides by using an analogous pyrazole‐based ligand.

Editorial

Editorial

Palladium-Catalyzed Alkene Carboalkoxylation Reactions of Phenols and Alcohols for the Synthesis of Carbocycles.

Intermolecular alkene difunctionalization reactions between terminal alkenes bearing a pendant aryl or alkenyl triflate electrophile and exogenous alcohol or phenol nucleophiles are described. These transformations afford substituted indanyl or alkylidenecyclopentyl ethers in high yield with excellent diastereoselectivity. The transformations proceed through intermolecular capture of an intermediate [Pd(II)-alkene]+[OTf]- complex by the alcohol or phenol nucleophile.

Synthesis of N‐alkyl‐N′‐aryl or Alkenylpiperazines: A Copper‐Catalyzed C–N Cross‐Coupling in the Presence of Aryl and Alkenyl Triflates and DABCO

Unsymmetrical piperazines are key constituents of many pharmaceuticals. Given that the selective introduction of an aryl and alkyl motif onto the piperazine is not always straightforward, direct arylation and alkenylation of 1,4‐diaza‐bicyclo[2.2.2]octane would obviate the inefficiencies associated with the preparation of these target molecules. We have utilized alkyl halides, aryl or alkenyl triflates, and 1,4‐diaza‐bicyclo[2.2.2]octane for the synthesis of N‐alkyl‐N′‐aryl or alkenylpiperazines. The optimum conditions are developed using CuCl, t‐BuOLi in NMP. Alkenyl triflates requires N,N′‐dimethylethylenediamine and higher temperature to afford the desired cross‐coupled product. Substrates bearing electron‐deficient and electron‐rich groups were successfully coupled under the optimum reaction conditions.

Pd-Catalyzed Regioselective 1,2-Difunctionalization of Vinylarenes with Alkenyl Triflates and Aryl Boronic Acids at Ambient Temperature.

A Pd-catalyzed highly regioselective 1,2-difunctionalization of vinylarenes is disclosed in which multisubstituted olefins are efficiently and conveniently constructed under ambient temperature with good compatibility and a broad substrate scope. Notably, a quarternary carbon center could be readily built up from 1,1-disubstituted styrenes, which are big challenges in the previous methods.

Palladium-catalyzed geometrically selective hydrogenation of (Z)-trifluoromethyl alkenyl triflate: an efficient approach to (Z) or (E)-3,3,3-trifluoropropenyl derivatives

A Pd-catalyzed hydrogenation of (Z)-trifluoromethyl alkenyl triflate providing either (Z)- or (E)-3,3,3-trifluoropropenyl derivatives with excellent divergent geometric control in good yield is described. Catalyzed by Pd(OAc)2/PPh3, the reduction of (Z)-trifluoromethyl alkenyl triflates with HSiEt3 gave (E)-3,3,3-trifluoropropenyl derivatives, and while using HCOOH/Et3N as the reducing agent, the (Z)-isomers were obtained through an elimination/hydrogenation tandem pathway. Both transformations showed excellent geometrical selectivity.

Terminal‐Selective Functionalization of Alkyl Chains by Regioconvergent Cross‐Coupling

AbstractHydrocarbons are still the most important precursors of functionalized organic molecules, which has stirred interest in the discovery of new C−H bond functionalization methods. We describe herein a new step‐economical approach that enables C−C bonds to be constructed at the terminal position of linear alkanes. First, we show that secondary alkyl bromides can undergo in situ conversion into alkyl zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross‐coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross‐coupling then provided access to the corresponding linear arylation product in only two steps.

Terminal-Selective Functionalization of Alkyl Chains by Regioconvergent Cross-Coupling.

Hydrocarbons are still the most important precursors of functionalized organic molecules, which has stirred interest in the discovery of new C-H bond functionalization methods. We describe herein a new step-economical approach that enables C-C bonds to be constructed at the terminal position of linear alkanes. First, we show that secondary alkyl bromides can undergo in situ conversion into alkyl zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross-coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross-coupling then provided access to the corresponding linear arylation product in only two steps.

Enantioselective Palladium-Catalyzed Alkenylation of Trisubstituted Alkenols To Form Allylic Quaternary Centers

In this report, we describe the generation of remote allylic quaternary stereocenters β, γ, and δ relative to a carbonyl in high enantioselectivity. We utilize a redox-relay Heck reaction between alkenyl triflates and acyclic trisubstituted alkenols of varying chain-lengths. A wide array of terminal (E)-alkenyl triflates are suitable for this process. The utility of this functionalization is validated further by conversion of the products, via simple organic processes to access remotely functionalized chiral tertiary acid, amine, and alcohol products.

Decarboxylative Aminomethylation of Aryl- and Vinylsulfonates through Combined Nickel- and Photoredox-Catalyzed Cross-Coupling.

A mild approach for the decarboxylative aminomethylation of aryl sulfonates by the combination of photoredox and nickel catalysis through C-O bond cleavage is described for the first time. A wide range of aryl triflates as well as aryl mesylates, tosylates and alkenyl triflates afford the corresponding products in good to excellent yields.

ChemInform Abstract: A Mild Preparation of Alkynes from Alkenyl Triflates.

AbstractA protocol for preparing alkynes from alkenyl triflates is reported.

Selenide-Catalyzed Stereoselective Construction of Tetrasubstituted Trifluoromethylthiolated Alkenes with Alkynes.

The efficient regio- and stereoselective construction of tetrasubstituted alkenes is challenging and very important. For this purpose, we have developed an efficient approach to synthesize tetrasubstituted trifluoromethylthiolated alkenes from simple alkynes in excellent regio- and stereoselectivities by selenide-catalyzed multicomponent coupling. Using this method, trifluoromethylthiolated alkenyl triflates and arenes were achieved. In particular, the triflates could be further converted into carbofunctionalized alkenes by palladium-catalyzed cross-coupling reactions. Our method provides a new pathway for the construction of trifluoromethylthiolated tricarboalkenes. This work presents the first example of selenide-catalyzed trifluoromethylthiolation of alkynes and enables the challenging functionalizations of alkynes.

ChemInform Abstract: Synthesis of (Z)‐α‐Trifluoromethyl Alkenyl Triflate: A Scaffold for Diverse Trifluoromethylated Species.

ChemInformVolume 47, Issue 41 Preparative Organic Chemistry ChemInform Abstract: Synthesis of (Z)-α-Trifluoromethyl Alkenyl Triflate: A Scaffold for Diverse Trifluoromethylated Species. Yilong Zhao, Yilong Zhao State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorYuhan Zhou, Yuhan Zhou State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorJuan Liu, Juan Liu State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorDongmei Yang, Dongmei Yang State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorLiang Tao, Liang Tao State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorYang Liu, Yang Liu State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorXiaoliang Dong, Xiaoliang Dong State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorJianhui Liu, Jianhui Liu State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorJingping Qu, Jingping Qu State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this author Yilong Zhao, Yilong Zhao State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorYuhan Zhou, Yuhan Zhou State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorJuan Liu, Juan Liu State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorDongmei Yang, Dongmei Yang State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorLiang Tao, Liang Tao State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorYang Liu, Yang Liu State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorXiaoliang Dong, Xiaoliang Dong State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorJianhui Liu, Jianhui Liu State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this authorJingping Qu, Jingping Qu State Key Lab. Fine Chem., Dalian Univ. Technol., Dalian 116024, Peop. Rep. ChinaSearch for more papers by this author First published: 22 September 2016 https://doi.org/10.1002/chin.201641053Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume47, Issue41September, 2016 RelatedInformation

Mechanism and Selectivity in the Pd-Catalyzed Difunctionalization of Isoprene.

The three-component coupling of isoprene, an alkenyl triflate, and styrenylboronic acid catalyzed by a palladium pyrox complex affords access to skipped dienes from simple chemical feedstocks. Unfortunately, the transformation proceeds with only moderate selectivity and yields. The reaction mechanism and factors responsible for the resulting regioselectivity were elucidated using M06/SDD/6-311++G(d,p) + SMD calculations. Distortion of the palladium coordination sphere in the transition structure of the migratory insertion step is found to control the 4,1- vs 1,x-selectivity. The calculated ΔΔG⧧ of 1.0 kcal/mol for this step is in excellent agreement with the experimentally observed selectivity of 1:9.9 disfavoring the 4,1-product. The transmetalation was found to be the regioselectivity determining step for the formation of the 1,2- vs 1,4-addition products. Systematic conformational searches for the transmetalation transition structure revealed a series of steric interactions between the t-Bu substituent on the ligand and the substrates in the model system that are balanced by additional repulsive interactions between the substrates and the pyridyl portion of the ligand. The combination of these effects leads to the low to moderate 1,2- vs 1,4-selectivity in the experimentally studied system.

Synthesis of (Z)-α-Trifluoromethyl Alkenyl Triflate: A Scaffold for Diverse Trifluoromethylated Species.

An efficient method for the synthesis of (Z)-selective α-trifluoromethyl alkenyl triflates is described. As an important fluorinated building block, it is utilized successfully for the synthesis of various trifluoromethyl derivatives such as diarylethylenes, enynes, alkynes, and benzofurans.