An Atom-Economic and Selective Ruthenium-Catalyzed Redox Isomerization of Propargylic Alcohols. An Efficient Strategy for the Synthesis of Leukotrienes

Abstract

Catalytic ruthenium complexes in conjunction with an indium cocatalyst and Bronsted acid isomerize primary and secondary propargylic alcohols in good yields to provide trans enals and enones exclusively. Readily available indenylbis(triphenylphosphine)ruthenium chloride in the presence of indium triflate and camphorsulfonic acid give the best turnover numbers and reactivity with the broadest range of substrates. Deuterium labeling experiments suggest that the process occurs through propargylic hydride migration followed by protic cleavage of the resultant vinylruthenium intermediate. Application of this method to the synthesis of leukotriene B4 demonstrates its utility and extraordinary selectivity.

Synthesis of dihydrobenzofurans and dihydroindoles by intramolecular Friedel-Crafts reaction of aryloxy- and arylamino-substituted propargylic alcohols

“…A series of other desiccants, such as CaH 2 and MgSO 4 , were also tested (entries 10, 11), and they displayed higher efficiency for the reaction. No significant formation of 2a was detected when other solvents, including MeNO 2 , toluene, MeCN and DCM were used (entries [12][13][14][15]. Decreasing the catalyst from 1 equivalent to 20 mol% had a drastic effect as only 14% of 2a was isolated (entry 16), indicating that stoichiometric catalyst was required for the transformation to occur.…”

“…[13][14][15][16][17][18][19] One of the most important applications of propargylic alcohols is the synthesis of allenes by the coupling of a nucleophiles with allenic carbocation intermediates, which were generated in situ by the Meyer-Schuster rearrangement. The allenes generated in situ could then undergo various cascade reactions to form many useful structural frameworks.…”

Epoxidation of alkenes with NaIO4 catalyzed by an efficient and reusable natural polymer-supported ruthenium(III) salophen catalyst

“…Immobilization of homogeneous catalysts on a solid support enables easy recovery and recycling of homogeneous catalysts and avoids their disadvantages with respect to handling and reusability of the catalyst [29]. Recently, ruthenium complexes have been developed as suitable catalysts in organic synthesis [30][31][32][33][34][35]. Also, Schiff base complexes of ruthenium(III) are used as potential catalysts for olefin epoxidation [36].…”

Stereoselective Synthesis of Exocyclic Tetrasubstituted Vinyl Halides via Ru-Catalyzed Halotropic Cycloisomerization of 1,6-Haloenynes

“…Remarkably, 8d was obtained cleanly, without any redox isomerization byproducts. 15 While a remote phenyl group ( 7i ) had little impact on the E/Z selectivity, a conjugated phenyl group ( 7e ) gave an E/Z ratio of 6:1.…”