Domino Rhodium/Palladium‐Catalyzed Dehydrogenation Reactions of Alcohols to Acids by Hydrogen Transfer to Inactivated Alkenes

Abstract

The combination of the d(8) Rh(I) diolefin amide [Rh(trop(2)N)(PPh(3))] (trop(2)N=bis(5-H-dibenzo[a,d]cyclohepten-5-yl)amide) and a palladium heterogeneous catalyst results in the formation of a superior catalyst system for the dehydrogenative coupling of alcohols. The overall process represents a mild and direct method for the synthesis of aromatic and heteroaromatic carboxylic acids for which inactivated olefins can be used as hydrogen acceptors. Allyl alcohols are also applicable to this coupling reaction and provide the corresponding saturated aliphatic carboxylic acids. This transformation has been found to be very efficient in the presence of silica-supported palladium nanoparticles. The dehydrogenation of benzyl alcohol by the rhodium amide, [Rh]N, follows the well established mechanism of metal-ligand bifunctional catalysis. The resulting amino hydride complex, [RhH]NH, transfers a H(2) molecule to the Pd nanoparticles, which, in turn, deliver hydrogen to the inactivated alkene. Thus a domino catalytic reaction is developed which promotes the reaction R-CH(2)-OH+NaOH+2 alkene-->R-COONa+2 alkane.

Nitrous Oxide as a Hydrogen Acceptor for the Dehydrogenative Coupling of Alcohols

“…However, these transformations require elevated temperatures, and the search for catalytic systems that enable the use of inexpensive hydrogen acceptors that allow for an easy work‐up of the reaction mixtures remains attractive. Unactivated olefins can be used as hydrogen acceptors in the presence of palladium nanoparticles supported on silica as a co‐catalyst . Oxygen from the air can also serve as a hydrogen acceptor in the dehydrogenative coupling of primary alcohols with water .…”

A Biologically Inspired Organometallic Fuel Cell (OMFC) That Converts Renewable Alcohols into Energy and Chemicals

“…We recently reported that the organometallic complex [Rh(trop 2 N)(PPh 3 )] (1) catalyses the oxidation of primary alcohols to give carboxylic acid derivatives in the presence of hydrogen acceptors A such as RR'C = O, olefins, or palladium nanoparticles in either homogeneous [9,10] or heterogeneous phase (Scheme 1). [11] The amido complex 1 is simply accessed by deprotonation of the precursor complex [Rh(OTf)-(trop 2 NH)(PPh 3 )] (2) under basic conditions (OTf = trifluoromethanesulfonate).…”

Chemical Constituents from the Fruits ofForsythia suspensaand Their Antimicrobial Activity

“…The crude extract was suspended into water and partitioned with chloroform to afford chloroform and water soluble fractions, respectively. Purification of the chloroform fraction of the methanol extracts of fruits of F. suspensa by a combination of chromatographic techniques yielded one new triterpene, 3 β -acetoxy-20 α -hydroxyursan-28-oic acid ( 1 ) (Figure 1), β -amyrin acetate ( 2 ) [22], taraxasterol acetate ( 3 ) [23], 3 β -acetyl-20,25-epoxy-dammarane-24 α -ol ( 4 ) [24], acetyl oleanolic acid ( 5 ) [25], betulinic acid ( 6 ) [26], labda-8(17),13 E -dien-15,18-dioic acid 15-methyl ester ( 7 ) [27], mixture of β -sitosterol ( 8 ) and stigmasterol ( 9 ) [28], ψ -taraxasterol ( 10 ) [29], 3 β -hydroxyanticopalic acid ( 11 ) [30], agatholic acid ( 12 ) [31], 3,4-dimethoxybenzoic acid ( 13 ) [32], vanillic acid ( 14 ) [33], syringic acid ( 15 ) [33], phillyrin ( 16 ) [15], p -hydroxyphenylacetic acid ( 17 ) [34], p -hydroxybenzoic acid ( 18 ) [33], and benzoic acid ( 19 ) [35], respectively. The water fraction was subjected to the reversed-phase Diaion HP-20 column chromatography and successive isolation to afford p -hydroxyphenylacetic acid ( 17 ), p -hydroxybenzoic acid ( 18 ), p -hydroxyphenylacetic acid methyl ester ( 20 ) [36], p -tyrosol ( 21 ) [37], hydroxytyrosol ( 22 ) [38], 2-furancarboxylic acid ( 23 ) [39], salidroside ( 24 ) [40], (6 S ,9 R )-roseoside ( 25 ) [41], forsythoside D ( 26 ) [8], methyl- α -D-glucopyranoside ( 27 ) [42], adoxosidic acid ( 28 ) [43], protocatechualdehyde ( 29 ) [44], esculetin ( 30 ) [45], caffeic acid ( 31 ) [46], trans -coumaric acid ( 32 ) [47], trans -ferulic acid ( 33 ) [48], and quercetin ( 34 ) [49], respectively.…”