Tandem Catalysis: Transforming Alcohols to Alkenes by Oxidative Dehydroxymethylation

Abstract

We report a Rh-catalyst for accessing olefins from primary alcohols by a C-C bond cleavage that results in dehomologation. This functional group interconversion proceeds by an oxidation-dehydroformylation enabled by N, N-dimethylacrylamide as a sacrificial acceptor of hydrogen gas. Alcohols with diverse functionality and structure undergo oxidative dehydroxymethylation to access the corresponding olefins. Our catalyst protocol enables a two-step semisynthesis of (+)-yohimbenone and dehomologation of feedstock olefins.

Transition Metal‐Mediated C−C Single Bond Cleavage: Making the Cut in Total Synthesis

“…In recent years,h owever,t here has been ap rofusion of C À Cb ond-cleavage methods that enable bond constructions beyond those employed in the syntheses covered in this Review and offer new opportunities for innovative total syntheses.One area ripe for innovation is the cleavage of CÀC bonds of unstrained rings,f or which an umber of effective methods have been published recently [59] but whose use in total synthesis has so far been limited (the synthesis of (À)lingzhiol described above being the sole exception highlighted in this Review). In contrast to using approaches to cleave CÀCb onds of strained rings,w ea nticipate that the cleavage of CÀCb onds of unstrained rings in total synthesis would both enable myriad retrosynthetic opportunities-as unstrained rings are far more common than strained rings in simple chemical building blocks-as well as help further curtail the lengths of syntheses,g iven that synthetic steps often must be expended to construct strained rings before subsequent CÀCb ond cleavage.I na ddition, opportunities remain for advancing the use of peripheral C À Cb ond cleavage in total synthesis,m oving beyond decarboxylative strategies;f or example,t he use of newly published methods for CÀCb ond cleavage on substrates at al ower oxidation state than the carboxylic acid (e.g.atthe alcohol or aldehyde oxidation state) [60] promises to streamline syntheses that often involve multiple steps for functional group interconversions.…”

Catalytic Isofunctional Reactions—Expanding the Repertoire of Shuttle and Metathesis Reactions

“…[37] They reported aRhcatalyzed dehydroformylation to transform aldehydes to the corresponding alkenes by transfer of hydrogen and carbon monoxide to as trained alkene,e ither norbornadiene or norbornene (Scheme 6A). [39] This enables direct access to alkenes from simple alcohol precursors. A plausible explanation for this is that the transfer to the strained alkene leads to an exothermic reaction and is thus irreversible under these conditions.F rom their mechanistic studies,the group of Dong proposed that the Rh complex 15 adds oxidatively across the C À Hbond of the aldehyde to form 16 (Scheme 6B).…”

Übergangsmetallvermittelte Spaltung von C‐C‐Einfachbindungen

“…Außerdem ergeben sich fürSpaltungen peripherer C-C-Bindungen in der Totalsynthese über decarboxylierende Strategien hinaus neue Einsatzmçglichkeiten;b eispielsweise verspricht die Anwendung neuer Methoden fürd ie C-C-Bindungsspaltung an Substraten in niedrigeren Oxidationszuständen als die Carbonsäure (z. B. Alkoholen oder Aldehyden) [60] eine Optimierung von Synthesen, die häufig mehrere Stufen zur Umwandlung funktioneller Gruppen bençtigen.…”