Dehydrogenative Heck Reaction Research Articles

Rhodaelectro-Catalyzed Synthesis of Pyrano[3,4-b]indol-1(9H)-ones via the Double Dehydrogenative Heck Reaction between Indole-2-carboxylic Acids and Alkenes

Rhodaelectro-Catalyzed Synthesis of Pyrano[3,4-<i>b</i>]indol-1(9<i>H</i>)-ones via the Double Dehydrogenative Heck Reaction between Indole-2-carboxylic Acids and Alkenes

Pd-catalyzed Intermolecular Dehydrogenative Heck Reactions of Six-membered Heteroarenes

The PdII-mediated cross-coupling of (hetero)arenes with alkenes may be an effective method for the formation of a C–C bond from two C–H bonds. This reaction was discovered by Fujiwara and his co-workers in 1967, which led to a number of reports that we first highlighted in 2011 (review with references till June 2010) and for which we retained the name “Dehydrogenative Heck Reaction” (DHR). The DHR of six-membered heteroarenes has been the subject of intensive research over the last ten years. The present review is limited to these dehydrogenative Heck reactions published since 2010, underlining the diversity of the procedures, mechanisms and intermediates that have been proposed along with some personal comments.

Pd-Catalyzed Intermolecular Dehydrogenative Heck Reactions of Five-Membered Heteroarenes

The Pd-mediated cross-coupling of (hetero)arenes with alkenes may be an effective method for the formation of a C–C bond from two C–H bonds. Discovered by Fujiwara and co-workers in 1967, this reaction led to a number of reports that we firstly highlighted in 2011 (review with references till June 2010) and for which, we retained the name “dehydrogenative Heck reaction”. The topic, especially the reactions of five-membered heteroarenes, has been the subject of intensive research over the last ten years. The present review is limited to these dehydrogenative Heck reactions published since 2010, underlining the progress of the procedures.

Introducing unactivated acyclic internal aliphatic olefins into a cobalt catalyzed allylic selective dehydrogenative Heck reaction.

Unactivated acyclic internal aliphatic olefins are often found to be unreactive in conventional alkenylation reactions. To address this problem, a cobalt catalyzed allylic selective dehydrogenative Heck reaction with internal aliphatic olefins has been developed. The method is highly regio- and stereoselective, the conditions are mild and a wide variety of functional groups can be tolerated. Remarkably, both internal and terminal aliphatic olefins can be employed, thereby significantly expanding the scope of alkenylation chemistry with aliphatic olefins.

Catalyst‐Controlled Regiodivergent Dehydrogenative Heck Reaction of 4‐Arylthiophene/Furan‐3‐Carboxylates

AbstractA catalyst‐controlled regiodivergent dehydrogenative Heck reaction of 4‐arylthiophene/furan‐3‐carboxylates has been realized. Use of a palladium catalyst led to the C‐5 alkenylation through electronic palladation, while a ruthenium catalyst favored the C‐2 alkenylation with the assistance of a directing group. This reaction exhibited good to excellent regioselectivities.magnified image

Switch to Allylic Selectivity in Cobalt-Catalyzed Dehydrogenative Heck Reactions with Unbiased Aliphatic Olefins

A unique C–H allylation has been discovered with unbiased aliphatic olefins. An intimate M–L affiliation between a high-valent cobalt catalyst and amino-quinoline derived benzamides has been found to be crucial for this unprecedented selectivity. An exemplary set of aliphatic olefins, high yields coupled with excellent regio- and stereoselectivity, and wide functional group tolerances are noteworthy. In addition, a catalytically competent organometallic Co(III) species has been identified through X-ray crystallography. This study is expected to facilitate new synthetic designs toward unconventional allylic selectivity with aliphatic olefins.

ChemInform Abstract: Ligand‐Promoted Reactivity of Alkenes in Dehydrogenative Heck Reactions of Furans and Thiophenes.

Abstract4,5‐Diazafluorenone is found to be an effective ligand for the dehydrogenative Heck reaction of cinnamic acid derivatives or stilbenes with thiophenes and furanes.

Aerobic palladium(II)-catalyzed dehydrogenative heck reaction in the synthesis of pyrenyl fluorophores. a photophysical study of β-pyrenyl acrylates in solution and in the solid state.

An aerobic dehydrogenative Heck reaction of pyrene (1a) and 2,7-di-tert-butylpyrene (1b) with ethyl acrylate is reported. The reaction is catalyzed by a Pd(OAc)2/4,5-diazafluoren-9-one (DAF) system and takes place in acetic or pivalic acid as solvents at 110-130 °C. The reaction of 1a afforded a 6:1 mixture of C-1- and C-4-alkenylated pyrenes (2a and 3a, respectively) in 71% yield. In the case of 1b, only a C-4-substituted product (3b) was formed in 46% yield. Compounds 2a and 3a,b exhibited fluorescence in solution and in the solid state. In chloroform and THF solution the fluorescence maxima were in the range of 440-465 nm, and quantum yields decreased in the order 2a > 3a> 3b. In the solid state, 3a,b showed blue-green fluorescence (ΦF = 0.26 and 0.14, respectively), whereas 2a emitted yellow-green fluorescence) (ΦF = 0.35). Besides blue-emitting monomers, the presence of green-emitting aggregated species (preformed dimers) in the crystals of 3a,b and red-emitting dynamic excimers in the crystals of 2a has been demonstrated. Single-crystal X-ray diffraction analyses of 2a and 3b confirmed π-stacking of pyrenyl moieties in the crystals of the former and the absence of stacking in the crystals of the latter compound.

Ligand‐Promoted Reactivity of Alkenes in Dehydrogenative Heck Reactions of Furans and Thiophenes

Abstract4,5‐Diazafluorenone was found to promote the dehydrogenative Heck reaction of furans and thiophenes with hindered alkenes. High stereoselectivity was achieved in the synthesis of β,β‐diaryl α,β‐unsaturated alkenes. A mechanism, based on ESI‐MS studies, kinetic experiments, and competitive reactions, was proposed. The ligand influences C–H bond activation, insertion of the alkenes, the stereodetermining step, and the aerobic regeneration of the catalyst.

Recent Developments in Pd-Catalyzed Oxidative Heck Cross Coupling Reaction of Arenes/Alkenes with Allylic Esters

The cross coupling reaction of arene with alkene generating substituted olefin through two sp(2)-C-H bond activation is named oxidative Heck reaction, dehydrogenative Heck reaction (DBR), or Fujiwara-Moritani reaction. In the past decades, these reactions have drawn much attention due to their C-C bond formations via direct C-H functionalization. However, only electron-deficient alkenes are effective coupling partners in most of these systems. The oxidative Heck reaction using electron-rich olefins such as allylic esters and ethers as the coupling partners has rarely been studied. Recently, several novel Pd-catalyzed strategies for cross coupling reactions of arenes/alkenes with allylic esters/ethers have been explored by us and other groups. This review will summarize the developments in this interesting and atom-economic area.

Pd催化苯乙烯脱氢氧化偶联研究

我们对未活化的苯乙烯末端烯烃进行了脱氢Heck反应的研究，运用Pd(acac)2做催化剂，Cu(OAc)2作氧化剂，并添加少量AgF，乙酸乙酯作溶剂，在100℃下反应24 h，苯乙烯直接脱氢得到1,4-二苯基-1,3-丁二烯，具有共轭结构，能作为许多有价值化合物的中间体，具有潜在的应用价值，我们还对该反应提出了一个可能的机理。 The work about dehydrogenative Heck reaction of unactivated terminal alkene of styrene was studied. Using Pd(acac)2 as catalyst, Cu(OAc)2 as oxidant, EtOAc as solvent, and adding some AgF, at 100˚C for 24 h, styrene was directly dehydrogenized to generate 1,4-dipheny-1,3-butadiene with conjugated construction which can be intermediate of many value compounds, so this reaction has potential value. A plausible mechanism was proposed.

ChemInform Abstract: Dehydrogenative Heck Reaction (Fujiwara—Moritani Reaction) of Unactivated Olefins with Simple Dihydropyrans under Aprotic Conditions.

AbstractIn the reaction with olefins only (E)‐products are observed but in most of the cases along with some homo‐coupling products.

Role of Mono-N-protected Amino Acid Ligands in Palladium(II)-Catalyzed Dehydrogenative Heck Reactions of Electron-Deficient (Hetero)arenes: Experimental and Computational Studies

We report here that mono-N-protected amino acids (MPAAs), an important environmentally compatible structural motif, enable acceleration of Pd(II)-catalyzed dehydrogenative Heck reactions between pyridines and electron-deficient arenes with simple alkenes, leading to diversely functionalized C3- or meta-selective alkenylated pyridines and benzenes via non-chelate-assisted C–H activation. A comprehensive theoretical study by DFT calculations discloses that the amino scaffold of the MPAA ligand facilely converts to an X-type ligand by an initial N–H activation, resulting in a relatively low activation barrier for the C–H cleavage of pyridine. Then a property reversal of the amino group from X-type to L-type ligand allows the alkene substitution to take place smoothly, while the carboxyl group enables the formation of an intramolecular hydrogen bond, significantly decreasing the activation barrier for the carbopalladation. The results of calculations and the kinetic isotopic effect measurement support a rate-...

Palladium-Catalyzed Enantioselective Dehydrogenative Heck Reaction

Palladium-Catalyzed Enantioselective Dehydrogenative Heck Reaction

Dehydrogenative Heck Reaction (Fujiwara–Moritani Reaction) of Unactivated Olefins with Simple Dihydropyrans under Aprotic Conditions

AbstractThe dehydrogenative Heck coupling (Fujiwara–Moritani reaction) of unactivated olefins with 3,4‐dihydro‐2H‐pyrans is described. The two main highlights of the work are the use of unconventional unactivated olefins as coupling partners in the palladium‐catalyzed reaction and the use of aprotic conditions for the coupling reaction of the acid‐labile dihydropyrans.magnified image

ChemInform Abstract: α‐Palladation of Imines as Entry to Dehydrogenative Heck Reaction: Aerobic Oxidative Cyclization of N‐Allylimines to Pyrroles.

We report here a palladium(II)-catalyzed oxidative cyclization reaction of N-allylimines derived from methyl ketones, typically acetophenones, affording pyrrole derivatives at room temperature under oxygen atmosphere. The reaction likely proceeds through α-palladation of the imine followed by olefin migratory insertion and β-hydride elimination, thus representing a new example of aerobic dehydrogenative Heck cyclization.

Aerobic Dehydrogenative Heck Reaction of Ferrocene with a Pd(OAc)2/4,5-Diazafluoren-9-one Catalyst

The aerobic dehydrogenative Heck alkenylation of ferrocene with alkenes, catalyzed by a Pd(OAc)2/4,5-diazafluoren-9-one system, is disclosed. Monoalkenylated ferrocenes were obtained in moderate yields and selectivities using various electron-poor alkenes. Oxygen at an atmospheric pressure was the sole oxidant. The reaction can be carried out at room temperature (several days) or at 70 °C (∼3 h).

ChemInform Abstract: Aerobic Dehydrogenative Heck Reactions of Heterocycles with Styrenes: A Negative Effect of Metallic Co‐Oxidants.

AbstractAerobic dehydrogenative Heck reactions of heterocycles with styrene derivatives are shown to be more efficient in the absence of metallic co‐oxidants.

α-Palladation of Imines as Entry to Dehydrogenative Heck Reaction: Aerobic Oxidative Cyclization ofN-Allylimines to Pyrroles

We report here a palladium(II)-catalyzed oxidative cyclization reaction of N-allylimines derived from methyl ketones, typically acetophenones, affording pyrrole derivatives at room temperature under oxygen atmosphere. The reaction likely proceeds through α-palladation of the imine followed by olefin migratory insertion and β-hydride elimination, thus representing a new example of aerobic dehydrogenative Heck cyclization.

Redox of ferrocene controlled asymmetric dehydrogenative Heck reaction via palladium-catalyzed dual C–H bond activation

A novel strategy of dehydrogenative Heck reaction controlled by redox process of ferrocene has been developed. Commercially available chiral amino acid as ligand realized asymmetric dehydrogenative Heck reaction, leading to planar-chiral ferrocene derivatives with excellent enantioselectivity and in good to excellent yields (up to 99% ee and 98% yield).