Palladium-Catalyzed Arylation and Vinylation of 4-Alkyl Substituted 2,3-Dihydrofurans: A Catalytic Sequence to Anti-Aldol Compounds

Hillers, Stephan; Reiser, Oliver

doi:10.1055/s-1995-4899

Cited by 23 publications

(10 citation statements)

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“…[571 (1a.P). [26,561 (Ip), [38] (IP) (with vinyl acetate to yield stilbenes), [84] (IIZ), [83a] (IIZa), [74] (IIIZa), [73] (IIIZP), [83b,c) (ketene acetals), [85] L86al (IP)…”

Section: Tetrasubstituted (Z)mentioning

confidence: 99%

Palladium‐Catalyzed Coupling of Organyl Halides to Alkenes — the Heck Reaction

Bräse¹,

Meijere²

1998

Metal‐Catalyzed Cross‐Coupling Reactions

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About 25 years ago, a Japanese and an American group simultaneously designed and executed palladium-catalyzed coupling reactions of aryl and alkenyl halides with alkenes [ 11. In subsequent investigations, Richard Heck and his group demonstrated the usefulness and rather broad scope of this new catalytic transformation. The real push to utilize this powerful C-C bond-forming process, however, started only about 12 years ago; now, an impressive number of publications has established the so-called Heck reaction [2] as an indispensable method in organic synthesis [3]. The applications range from the preparation of hydrocarbons, novel polymers, and dyes to new advanced enantioselective syntheses of natural products. The simultaneous developments of mechanistically related variants, namely the Kumada, Suzuki, Stille, and Negishi coupling reactions (Chapters 1, 2, and 4 in this book, respectively) of metallated alkenes and arenes with alkenes or the metalcatalyzed formation and cycloisomerization of enynes have drawn profit from the improvement of and mechanistic insights into the Heck reaction. This, of course, applies conversely as well. Using only a catalytic amount of a palladium(0) complex, the Heck reaction can bring about unprecedented structural changes, particularly when conducted intramolecularly. Although the potential of this palladium-catalyzed process has not yet been at all fully explored, it is appropriate to say, even at this stage, that the Heck reaction is one of the true "power tools" in contemporary organic synthesis [4].In this chapter, an attempt is made to summarize the current state of understanding of the basics of the mechanism, to provide an overview over the diverse and sometimes mysterious compositions of applicable catalyst "cocktails", and to review important recent developments and applications of this reaction principle. Principles The MechanismEven at an early stage in the evolution of the Heck reaction into a facile method for the preparation of alkenyl-and aryl-substituted alkenes, reasonable concepts for the mechanism emerged, which could serve at least as working hypotheses. 99Metal-catalyzed Cross-coupling Reactions Edited by François Diederich, Peter J. Stang A coordinatively unsaturated 14-electron palladium(0) complex, usually coordinated with weak donor ligands (usually tertiary phosphanes), has meanwhile been proven to be the catalytically active species [5]. This complex is mostly generated in situ. Tetrakis(triphenyIphosphane)palladium(O) [6], which exists in an equilibrium with tris(triphenylphosphane)palladium(O) and free triphenylphosphane in solution, is frequently employed. The endergonic loss of a second phosphane ligand [7] leads to the catalytically active bis(triphenylphosphane)palladium(O). However, palladium(I1) complexes such as bis(tripheny1phosphane)palladium dichloride or palladium acetate, which are easily reduced (e.g. by triarylphosphanes; see below) in the reaction medium, are more commonly employed for convenience, as they are inherently stable towards ...

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“…[571 (1a.P). [26,561 (Ip), [38] (IP) (with vinyl acetate to yield stilbenes), [84] (IIZ), [83a] (IIZa), [74] (IIIZa), [73] (IIIZP), [83b,c) (ketene acetals), [85] L86al (IP)…”

Section: Tetrasubstituted (Z)mentioning

confidence: 99%

Palladium‐Catalyzed Coupling of Organyl Halides to Alkenes — the Heck Reaction

Bräse¹,

Meijere²

1998

Metal‐Catalyzed Cross‐Coupling Reactions

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“…Palladium-catalyzed arylation of 2 proceeds highly diastereoselectively to yield exclusively trans-disubstituted 2,3-dihydrofurans 4 (48-67%), which gave rise to anti-aldol compounds 3 (>90%) on subsequent oxidative cleavage by ozonolysis. [1] Results and Discussion However, the situation appears to be more complicated: the most crucial point seems to be the question if ligand exchange remains possible under pressure [4] so that a catalytic cycle can occur. There are two distinct mechanistic pathways by which ligand exchange reactions can take place.…”

Section: Introductionmentioning

confidence: 99%

The Influence of High Pressure in Palladium Catalyzed Coupling Reactions.

Hillers

Mengel

Bodmann

et al. 1998

THE REVIEW OF HIGH PRESSURE SCIENCE AND TECHNOLOGY

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The influence of high pressure (1-10 kbar) in solution on palladium catalyzed coupling reactions is examined both under the aspect of reactivity as well as selectivity. We present evidence that pressure can considerably accelerate such reactions as well as dramtically increase the turnover numbers of the catalysts. Moreover, new catalytic reactions become possible by using pressure: we present here our preliminary results on palladium catalyzed acylations of alkenes and the synthesis of trisubstituted alkenes by a new domino process combining the Horner-Wadsworth-Emmons and the Heck reaction. [palladium, alkenes, c ,f l-unsaturated ketones, Heck reaction, Horner-Wadsworth-Emmons reaction]

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“…Interestingly, 2-( p -tolyl)-2,3-dihydrofuran 1c obtained from an independent Heck cross-coupling reaction , also proved a competent partner delivering 3n as a single diastereoisomer in 67% yield and 91% ee (Figure B). More remarkably, trans -3-methyl-2-( p -tolyl)-2,3-dihydrofuran 1d , afforded the corresponding carboetherification product 3o with four contiguous stereocenters in 53% yield, 10:1 dr, and 96% ee (Figure C). Of note, an optically active tetrahydrofurobenzofurans with such a level of stereochemical complexity would certainly be difficult to prepare by conventional methods…”

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confidence: 98%