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Adam F. Littke

Bio: Adam F. Littke is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Aryl & Stille reaction. The author has an hindex of 14, co-authored 21 publications receiving 6927 citations.

Papers
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TL;DR: This review summarizes both the seminal early work and the exciting recent developments in the area of palladium-catalyzed couplings of aryl chlorides.
Abstract: Collectively, palladium-catalyzed coupling reactions represent some of the most powerful and versatile tools available to synthetic organic chemists. Their widespread popularity stems in part from the fact that they are generally tolerant to a large number of functional groups, which allows them to be employed in a wide range of applications. However, for many years a major limitation of palladium-catalyzed coupling processes has been the poor reactivity of aryl chlorides, which from the standpoints of cost and availability are more attractive substrates than the corresponding bromides, iodides, and triflates. Traditional palladium/triarylphosphane catalysts are only effective for the coupling of certain activated aryl chlorides (for example, heteroaryl chlorides and substrates that bear electron-withdrawing groups), but not for aryl chlorides in general. Since 1998, major advances have been described by a number of research groups addressing this challenge; catalysts based on bulky, electron-rich phosphanes and carbenes have proved to be particularly mild and versatile. This review summarizes both the seminal early work and the exciting recent developments in the area of palladium-catalyzed couplings of aryl chlorides.

2,377 citations

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TL;DR: In this paper, the authors used Pd2(dba)3/P(t-Bu)3 as a catalyst for Suzuki cross-coupling of aryl and vinyl triflates.
Abstract: Through the use of Pd2(dba)3/P(t-Bu)3 as a catalyst, a wide range of aryl and vinyl halides, including chlorides, undergo Suzuki cross-coupling with arylboronic acids in very good yield, typically at room temperature; through use of Pd(OAc)2/PCy3, a diverse array of aryl and vinyl triflates react cleanly at room temperature. Together, these two catalyst systems cover a broad spectrum of commonly encountered substrates for Suzuki couplings. Furthermore, they display novel reactivity patterns, such as the selective cross-coupling by Pd2(dba)3/P(t-Bu)3 of an aryl chloride in preference to an aryl triflate, and they can be used at low loading, even for reactions of aryl chlorides. Preliminary mechanistic work indicates that a palladium monophosphine complex is the active catalyst in the cross-coupling of aryl halides.

1,413 citations

Journal ArticleDOI
TL;DR: This development provides a general solution to a long-standing limitation of this extremely powerful process-the poor reactivity of inexpensive and readily accessible aryl chlorides.
Abstract: From only commercially available reagents a wide array of Suzuki cross-couplings of aryl chlorides with arylboronic acids can be effected in excellent yield [Eq. (a)]. This development provides a general solution to a long-standing limitation of this extremely powerful process-the poor reactivity of inexpensive and readily accessible aryl chlorides. dba=dibenzylideneacetone.

642 citations

Journal ArticleDOI
TL;DR: In the presence of Cy2NMe, Pd/P(t-Bu)3 serves as an exceptionally mild and versatile catalyst for Heck reactions of aryl chlorides and bromides, representing an advance over previously reported catalysts for these Heck coupling processes.
Abstract: In the presence of Cy2NMe, Pd/P(t-Bu)3 serves as an exceptionally mild and versatile catalyst for Heck reactions of aryl chlorides and bromides. A sterically and electronically diverse array of aryl bromides, as well as activated aryl chlorides, couple with a range of mono- and disubstituted olefins at room temperature, furnishing the arylated product with high E/Z stereoselection. The corresponding reactions of a broad spectrum of electron-neutral and electron-rich aryl chlorides proceed at elevated temperature, also with high selectivity. In terms of scope and mildness, Pd/P(t-Bu)3/Cy2NMe represents an advance over previously reported catalysts for these Heck coupling processes.

604 citations

Journal ArticleDOI
TL;DR: Palladiumkatalysierte kupplungen gehoren zu den leistungsfahigsten and vielseitigsten Reaktionen, die dem organischen Chemiker fur die Synthese zur Verfugung stehen as mentioned in this paper.
Abstract: Palladiumkatalysierte Kupplungen gehoren zu den leistungsfahigsten und vielseitigsten Reaktionen, die dem organischen Chemiker fur die Synthese zur Verfugung stehen. Ihre grose Beliebtheit ruhrt teilweise daher, dass sie bei den Umsetzungen gewohnlich viele funktionelle Gruppen tolerieren, was ihre breite Verwendung in vielen Bereichen ermoglicht. Allerdings unterlagen die palladiumkatalysierten Kupplungen jahrelang grosen Einschrankungen durch die geringe Reaktivitat der Arylchloride; diese Verbindungen sind in Bezug auf Kosten und Verfugbarkeit attraktivere Substrate als die entsprechenden Bromide, Iodide und Triflate. Herkommliche Palladium/Triarylphosphan-Katalysatoren setzten nur bestimmte aktivierte Arylchloride um (z. B. Heteroarylchloride und Substrate mit elektronenanziehenden Gruppen), nicht aber Arylchloride generell. Seit 1998 haben mehrere Forschungsgruppen bedeutende Fortschritte hinsichtlich dieser Herausforderung beschrieben; Katalysatoren mit voluminosen, elektronenreichen Phosphanen und Carbenen erwiesen sich als sehr vielseitig und ermoglichen besonders milde Reaktionsbedingungen. Dieser Aufsatz fasst die fruhen, wegweisenden Arbeiten und die spannenden neuartigen Entwicklungen auf dem Gebiet der palladiumkatalysierten Kupplungen von Arylchloriden zusammen.

468 citations


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TL;DR: A review of palladium-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle can be found in this paper.
Abstract: Pick your Pd partners: A number of catalytic systems have been developed for palladium-catalyzed CH activation/CC bond formation. Recent studies concerning the palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle are discussed (see scheme), and the versatility and practicality of this new mode of catalysis are presented. Unaddressed questions and the potential for development in the field are also addressed. In the past decade, palladium-catalyzed CH activation/CC bond-forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming CC bonds from CH bonds: PdII/Pd0, PdII/PdIV, Pd0/PdII/PdIV, and Pd0/PdII catalysis. A more detailed discussion is then directed towards the recent development of palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle. Despite the progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge.

3,533 citations

Journal ArticleDOI
TL;DR: s, or keywords if they used Heck-type chemistry in their syntheses, because it became one of basic tools of organic preparations, a natural way to make organic preparations.
Abstract: s, or keywords if they used Heck-type chemistry in their syntheses, because it became one of basic tools of organic preparations, a natural way to

3,373 citations

Journal ArticleDOI
TL;DR: A number of improvements have developed the former process into an industrially very useful and attractive method for the construction of aryl -aryl bonds, but the need still exists for more efficient routes whereby the same outcome is accomplished, but with reduced waste and in fewer steps.
Abstract: The biaryl structural motif is a predominant feature in many pharmaceutically relevant and biologically active compounds. As a result, for over a century 1 organic chemists have sought to develop new and more efficient aryl -aryl bond-forming methods. Although there exist a variety of routes for the construction of aryl -aryl bonds, arguably the most common method is through the use of transition-metalmediated reactions. 2-4 While earlier reports focused on the use of stoichiometric quantities of a transition metal to carry out the desired transformation, modern methods of transitionmetal-catalyzed aryl -aryl coupling have focused on the development of high-yielding reactions achieved with excellent selectivity and high functional group tolerance under mild reaction conditions. Typically, these reactions involve either the coupling of an aryl halide or pseudohalide with an organometallic reagent (Scheme 1), or the homocoupling of two aryl halides or two organometallic reagents. Although a number of improvements have developed the former process into an industrially very useful and attractive method for the construction of aryl -aryl bonds, the need still exists for more efficient routes whereby the same outcome is accomplished, but with reduced waste and in fewer steps. In particular, the obligation to use coupling partners that are both activated is wasteful since it necessitates the installation and then subsequent disposal of stoichiometric activating agents. Furthermore, preparation of preactivated aryl substrates often requires several steps, which in itself can be a time-consuming and economically inefficient process.

3,204 citations

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TL;DR: This Review highlights recent applications of controlled microwave heating in modern organic synthesis, and discusses some of the underlying phenomena and issues involved.
Abstract: Although fire is now rarely used in synthetic chemistry, it was not until Robert Bunsen invented the burner in 1855 that the energy from this heat source could be applied to a reaction vessel in a focused manner. The Bunsen burner was later superseded by the isomantle, oil bath, or hot plate as a source for applying heat to a chemical reaction. In the past few years, heating and driving chemical reactions by microwave energy has been an increasingly popular theme in the scientific community. This nonclassical heating technique is slowly moving from a laboratory curiosity to an established technique that is heavily used in both academia and industry. The efficiency of "microwave flash heating" in dramatically reducing reaction times (from days and hours to minutes and seconds) is just one of the many advantages. This Review highlights recent applications of controlled microwave heating in modern organic synthesis, and discusses some of the underlying phenomena and issues involved.

3,044 citations