Katalytische Markownikow‐ und Anti‐Markownikow‐Funktionalisierung von Alkenen und Alkinen

Abstract

Reaktionen zur selektiven Veredelung von Alkenen zählen zu den wichtigsten Methoden in der Organischen Synthese. Durch die Entwicklung von Übergangsmetallkatalysatoren in den letzten Jahrzehnten können heute alle Arten von Selektivität bei einer Vielzahl von Transformationen effizient gesteuert werden. Auch 100 Jahre nach dem Tod von Vladimir Markownikow – dem Pionier auf diesem Gebiet – ist die regioselektive Funktionalisierung von Alkenen und Alkinen immer noch ein wichtiges Forschungsziel: Besonders die Anti‐Markownikow‐Addition von Sauerstoff‐ und Stickstoff‐Nucleophilen an aliphatische Alkene und Alkine verfügt über großes industrielles Potenzial. In diesem Aufsatz werden neuere Entwicklungen auf diesem Gebiet beschrieben. Eine Auswahl aktueller Beispiele zeigt, wie die Regioselektivität durch die Wahl des Katalysators gesteuert werden kann.

Atom Economic Ruthenium‐Catalyzed Synthesis of Bulky β‐Oxo Esters

“…[3,4] Ruthenium catalysts are known to activate alkynes towards nucleophilic attack by coordination of the triple bond to the electrophilic metal center. [5,6] Depending on the tautomerizationb etween h 2 -alkyne and vinylidene binding modes the ruthenium complexesp romote either the Markovnikov addition or affordt he anti-Markovnikovp roducts by nucleophilic attack at the a-carbon of the vinylidenea nalogues (Scheme 1). [7][8][9] Then ucleophilic addition of carboxylic acids to terminal alkynes is an elegant method to produce enol esters.…”

“…[27][28][29] Thef irst catalytic system which was able to generate b-oxo estersw as described by Mitsudo andW atanabe. [30] They employed am ixture composed of bis(h 5 -cyclooctadienyl)ruthenium, P(n-Bu) 3 [11,[27][28][29]31,32] In addition, Cadierno and co-workers have shown that ruthenium(II) complexes containingh ydrosoluble phosphine ligands enable the formation of b-oxo estersi na queous medium. [27] Recently,w ec ould show for the first time that mononuclear ruthenium compoundso ft he type [Ru(CO) 2 (PPh 3 ) 2 (O 2 CR) 2 ]( R= CH 2 OCH 3 , i-Pr, t-Bu, 2-cyclo-C 4 H 3 O, Ph) are efficientc atalysts for the addition of carboxylic acids to propargylic alcohols,e ven when challengings ubstrates were applied.…”

Enantioselective Rhodium‐Catalyzed Synthesis of Branched Allylic Amines by Intermolecular Hydroamination of Terminal Allenes

“…[2,3] Catalytic enantioselective intermolecular hydroamination is a highly attractive, atom economical approach for the synthesis of non-racemic amines and their derivatives, and has been the subject of much attention. [4] Despite extensive effort, efficient methods for catalytic enantioselective intermolecular hydroamination are rare. [5] Although the enantioselective intermolecular hydroamination of allenes would be an efficient method for the synthesis of a-chiral allylic amines, [6,7] only one example has been reported, which requires internal allenes, has a limited scope, and provides only moderate levels of enantioselectivity (Scheme 1 a).…”

Transition Metal‐Catalyzed Asymmetric Hydroamination of Alkenes (AHA)

“…(2)] fashion. [2,3] Therefore, from an industrial point of view this reaction could be a highly useful and efficient method for the synthesis of a wide variety of industrially relevant basic and fine chemicals, as well as pharmaceuticals, from readily available and inexpensive starting materials.…”