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Heck Reaction—State of the Art catalysts Review Heck Reaction—State of the Art ID SangeetaReview Jagtap DepartmentHeck of Reaction—State Chemistry, Baburaoji Gholap College,of the Sangvi, Art Pune 411027, India; [email protected]; Tel.: +91-20-2728-0204 Sangeeta Jagtap Received: 20 August 2017; Accepted: 6 September 2017; Published: 11 September 2017 Department of Chemistry, Baburaoji Gholap College, Sangvi, Pune 411027, India; Abstract:[email protected];The Heck reaction is one Tel.: of+91 the‐20‐2728 most‐0204 studied coupling reactions and is recognized with the NobelReceived: Prize in 20 Chemistry.August 2017; Accepted: Thousands 6 September of articles, 2017; hundreds Published: 11 of September reviews and2017 a number of books have been published on this topic. All reviews are written exhaustively describing the various aspects of HeckAbstract: reaction The andHeck refer reaction to the is one work of donethe most hitherto. studied Looking coupling atreactions the quantum and is recognized of the monographs with published,the Nobel and Prize the in reviews Chemistry. based Thousands on them, of articles, we found hundreds a necessity of reviews to summarize and a number all of reviews books on have been published on this topic. All reviews are written exhaustively describing the various Heck reaction about catalysts, ligands, suggested mechanisms, conditions, methodologies and the aspects of Heck reaction and refer to the work done hitherto. Looking at the quantum of the compoundsmonographs formed published, via Heck and reaction the reviews in one based review on andthem, generate we found a resource a necessity of information.to summarize Oneall can find almostreviews allon the Heck catalysts reaction used soabout far forcatalysts, Heck reaction ligands, in suggested this review. mechanisms, conditions, methodologies and the compounds formed via Heck reaction in one review and generate a resource Keywords:of information.Heck reaction; One can reviews;find almost C-C all coupling;the catalysts catalysis; used so far mechanism; for Heck reaction application in this review. Keywords: Heck reaction; reviews; C‐C coupling; catalysis; mechanism; application 1. Introduction The1. Introduction new era of research started after the introduction of coupling reactions, i.e., carbon–carbon bond forming reactions like Heck [1], Suzuki [2], Sonogoshira [3], Negishi [4], Kumada [5], Stille [6], The new era of research started after the introduction of coupling reactions, i.e., carbon–carbon Tsuji-Trostbond forming [7], etc. reactions These reactions like Heck have [1], Suzuki played [2], an Sonogoshira enormously [3], decisive Negishi and [4], importantKumada [5], role Stille in [6], shaping chemicalTsuji‐ synthesisTrost [7], etc. and These have reactions revolutionized have played the way an oneenormously thinks aboutdecisive synthetic and important organic role chemistry. in The Heckshaping reaction chemical (Equation synthesis (1))and ishave used revolutionized extensively the in manyway one syntheses, thinks about including synthetic agrochemical, organic fine chemicals,chemistry. The pharmaceutical, Heck reaction etc.(Equation The reaction(1)) is used was extensively introduced in bymany Mizoroki syntheses, [8] including and Heck [9] independentlyagrochemical, more fine thanchemicals, four pharmaceutical, decades ago. etc. It has The drawn reaction much was introduced attention by due Mizoroki to high [8] efficiency and and simplicity.Heck [9] independently Heck methodology more than is four attractive decades from ago. a It synthetic has drawn point much of attention view because due to of high its high chemoselectivityefficiency and andsimplicity. mild reactionHeck methodology conditions is attractive along with from low a synthetic toxicity point and of cost view of because the reagent of if, specifically,its high thechemoselectivity catalyst is recycled. and mild reaction conditions along with low toxicity and cost of the reagent if, specifically, the catalyst is recycled. (1) (1) The Heck reaction is described as a vinylation or arylation of olefins where a large variety of The Heck reaction is described as a vinylation or arylation of olefins where a large variety of olefins can be used, like derivatives of acrylates, styrenes or intramolecular double bonds. The aryl olefinshalide can variants be used, developed like derivatives in addition of to acrylates, typical aryl styrenes bromides or and intramolecular iodides are aromatic double triflates, bonds. aroyl The aryl halidechlorides, variants aryl developed sulfonyl in chlorides, addition aromatic to typical diazonium aryl bromides salts, aroyl and iodidesanhydrides, are aromatic aryl chlorides triflates, and aroyl chlorides,arylsilanols. aryl sulfonyl The catalyst chlorides, is the essential aromatic part of diazonium a reaction where salts, a aroyl variety anhydrides, of metals along aryl with chlorides a huge and arylsilanols.range of Theligands catalyst is studied. is the Significant essential progress part of a for reaction the preparation where a and variety characterization of metals along of variety with of a huge rangeligands of ligands and catalysts is studied. has Significantbeen made for progress avoiding for protection the preparation and deprotection and characterization procedures, therefore of variety of ligandsallowing and catalysts for syntheses has beento be carried made forout avoiding in fewer steps. protection Development, and deprotection novel catalytic procedures, properties thereforeand allowingextensive for syntheses mechanistic to studies be carried are summarized out in fewer in steps. several Development, reviews based novel on seminal catalytic work properties of many and researchers and reviewers as described in following sections. Palladium is usually the preferred metal extensive mechanistic studies are summarized in several reviews based on seminal work of many as it tolerates a wide variety of functional groups and it has a remarkable ability to assemble C‐C researchers and reviewers as described in following sections. Palladium is usually the preferred metal bonds between appropriately functionalized substrates. Most palladium based methodologies as it toleratesproceed with a wide stereo variety‐ and of regioselectivity functional groups and andwith it excellent has a remarkable yields. Generally, ability to the assemble less crowded C-C bonds between appropriately functionalized substrates. Most palladium based methodologies proceed with Catalysts 2017, 7, 267; doi:10.3390/catal7090267 www.mdpi.com/journal/catalysts Catalysts 2017, 7, 267; doi:10.3390/catal7090267 www.mdpi.com/journal/catalysts Catalysts 2017, 7, 267 2 of 53 stereo- and regioselectivity and with excellent yields. Generally, the less crowded structure is preferred during Heck reaction, and often favours a trans product. Few mechanisms are also supported by the discussionCatalysts 2017 on, 7 the, 267 regioselectivity and stereoselectivity of Heck reaction. 2 of 53 Sometimes compounds such as TBAB (Tetra butyl ammonium bromide) are added in the reactionstructure mixture is preferred along with during organic Heck reaction, or inorganic and basesoften favours needed a for trans the product. sequestration Few mechanisms of acid generated. are Typicalalso supported solvents for by the discussion Heck reaction on the are regioselectivity dipolar aprotic and solvents stereoselectivity like DMF of Heck (dimethyl reaction. formamide) and NMPSometimes (N-methyl-2-pyrrolidone), compounds such as however, TBAB (Tetra the reaction butyl ammonium is also performed bromide) in manyare added other in different the reaction mixture along with organic or inorganic bases needed for the sequestration of acid solvents and in fact there are large numbers of reviews dedicated to the use of various solvents. generated. Typical solvents for the Heck reaction are dipolar aprotic solvents like DMF (dimethyl Besides these, many manuscripts describe the reaction in the absence of one of the component (other formamide) and NMP (N‐methyl‐2‐pyrrolidone), however, the reaction is also performed in many thanother substrates) different such solvents as ligand and in free,fact there organic are large solvent numbers free and of reviews so on. Recent dedicated publications to the use of also various describe howsolvents. to recover Besides used these, catalyst many specially manuscripts using aqueous describe medium the reaction which in implies the absence the potential of one forof greenerthe approachcomponent for organic (other than reactions. substrates) such as ligand free, organic solvent free and so on. Recent publicationsThere are aalso large describe number how of to excellent recover used reviews catalyst available specially on Heckusing reactionaqueous andmedium related which topics basedimplies on applications, the potential for mechanism, greener approach quest for for high organic turn reactions. over numbers (TONs), asymmetric synthesis, separationThere techniques, are a large etc. number In addition of excellent to this, reviews there are available a few manuscripts on Heck reaction that give and a generalrelated topics overview aboutbased Heck on reaction,applications, some mechanism, of them are quest detailed for high and turn some over are numbers not so descriptive. (TONs), asymmetric Many reviews synthesis, discuss variousseparation catalysis techniques, techniques etc. with In addition certain aspectsto this, wherethere are along a few with manuscripts the Heck reaction, that give other
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