Abstract:A series of half-sandwich phosphoramidite complexes of ruthenium were synthesized and employed as catalysts in the atom-economical formation of b-oxo esters from carboxylic acids and propargylic alcohols. Reaction of the phosphoramidites (R)-BINOL-PNR 2 (R = Me, 1a; i-Pr, 1b; benzyl, 1c) and (rac)-6,6'-dibromo-BINOL-PNMe 2 (1d) with the di- propargylic alcohols and carboxylic acids. Standard conditions involve cyclohexane solvent, propargylic alcohol (1.0 equiv.), carboxylic acid (1.0 equiv.), ruthenium cataly… Show more
“…[27] So far, just with complex[ RuCl 2 (pcymene){(R)}-BINOL-N,N-dibenzyl-phosphoramidite}] (14)r eported by Bauer et al acceptable yields in the conversion of 1,1-diphenylprop-2-yn-1-ol (1i)t o benzoic acid 2-oxo-1,1-diphenylpropyl ester (3i)w ere obtained. [28] All other systems failed in this conversion as they could only detect trace amounts of the desired product. [27,46] By applying catalyst 6g we could now isolate7 4% of product 3i in 4hat 80 8 8C, whereas with complex 14 just 68% after 5hat 90 8 8Cw ere achieved.…”
Section: Catalytic Experimentsmentioning
confidence: 98%
“…This factc an be explained by af acilitated activation of the electron-rich C Ct riple bondb yc oordination of the propargylic alcohol to the electrophilic ruthenium atom. However, the low yields obtained with electron-rich substrates suggest that not only the formation of the b-oxo esters is accelerated, but also that undesireds ider eactions take place.F or this reason the crude reactionm ixturesw ere analyzed by GC-MS.T hereby, olefinic side productsr esulting from the cleavageo ft he C Cb ond [27,28,47] or a,b-unsaturated vinyl aldehydesa rising from aM eyer-Schuster-type rearrangement [46,48] of the propargylic alcohol were observed. Bothr eactionp athways have already been reported to occur in the ruthenium-catalyzed addition of carboxylic acids to propargylic alcohols.…”
Section: Catalytic Experimentsmentioning
confidence: 99%
“…[27][28][29] Results and Discussion Synthesis 2 ] with basic phosphinel igands (6a,R= n-Bu; 6b,R= pMeO-C 6 H 4 ; 6c,R= p-Me-C 6 H 4 ; 6d,R= Ph) were prepared starting from Ru 3 (CO) 12 (4)b yasingle step conversion with the respective phosphine 5 and benzoic acid (2a)a nalogouslyt oaprocedure described by Bianchi [35] (Scheme 4).…”
Section: Scheme3mentioning
confidence: 99%
“…[4,16,26] Ther esulting enol ester D undergoesa ni ntramolecular transesterification to the alkenyl derivative E,which after keto-enol tautomerizationand protonation releases the b-oxo ester andr egenerates the catalytically active ruthenium species (Scheme 3). [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.…”
Section: Introductionmentioning
confidence: 99%
“…[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.…”
Ruthenium complexes with the formulae Ru(CO) 2 (PR 3 ) 2 (O 2 CPh) 2 [6a-h;R = n-Bu, p-MeO-C 6 H 4 , p-Me-C 6 H 4 ,P h, p-Cl-C 6 H 4 , m-Cl-C 6 H 4 , p-CF 3 -C 6 H 4 , m,m'-(CF 3 ) 2 C 6 H 3 ]w ere prepared by treatment of triruthenium dodecacarbonyl [Ru 3 (CO) 12 ]w ith the respective phosphine and benzoic acid or by the conversion of Ru(CO) 3 (PR 3 ) 2 (8e-h)w ith benzoic acid. During the preparation of 8,r uthenium hydride complexes of type Ru(CO)(PR 3 ) 3 (H) 2 (9g, h)c ould be isolated as side products. Them olecular structures of the newly synthesizedc omplexes in the solid state are discussed. Compounds 6a-h were found to be highly effective catalysts in the addition of carboxylic acids to propargylic alcohols to give valuable b-oxo esters.T he catalyst screening revealed ac onsiderably influence of the phosphine'se lectronicn ature on the resulting activities. Theb est performances were obtained with complexes 6g and 6h,f eaturing electron-withdrawing phosphine ligands.A dditionally,c atalyst 6g is very active in the conversion of sterically demanding substrates,l eading to ab road substrate scope.T he catalytic preparation of simple as wella sc hallenging substrates succeeds with catalyst 6g in yields that often exceed those of established literature systems.F urthermore,t he reactions can be carriedo ut with catalyst loadings down to 0.1 mol% andr eactiont emperatures down to 50 8 8C.
“…[27] So far, just with complex[ RuCl 2 (pcymene){(R)}-BINOL-N,N-dibenzyl-phosphoramidite}] (14)r eported by Bauer et al acceptable yields in the conversion of 1,1-diphenylprop-2-yn-1-ol (1i)t o benzoic acid 2-oxo-1,1-diphenylpropyl ester (3i)w ere obtained. [28] All other systems failed in this conversion as they could only detect trace amounts of the desired product. [27,46] By applying catalyst 6g we could now isolate7 4% of product 3i in 4hat 80 8 8C, whereas with complex 14 just 68% after 5hat 90 8 8Cw ere achieved.…”
Section: Catalytic Experimentsmentioning
confidence: 98%
“…This factc an be explained by af acilitated activation of the electron-rich C Ct riple bondb yc oordination of the propargylic alcohol to the electrophilic ruthenium atom. However, the low yields obtained with electron-rich substrates suggest that not only the formation of the b-oxo esters is accelerated, but also that undesireds ider eactions take place.F or this reason the crude reactionm ixturesw ere analyzed by GC-MS.T hereby, olefinic side productsr esulting from the cleavageo ft he C Cb ond [27,28,47] or a,b-unsaturated vinyl aldehydesa rising from aM eyer-Schuster-type rearrangement [46,48] of the propargylic alcohol were observed. Bothr eactionp athways have already been reported to occur in the ruthenium-catalyzed addition of carboxylic acids to propargylic alcohols.…”
Section: Catalytic Experimentsmentioning
confidence: 99%
“…[27][28][29] Results and Discussion Synthesis 2 ] with basic phosphinel igands (6a,R= n-Bu; 6b,R= pMeO-C 6 H 4 ; 6c,R= p-Me-C 6 H 4 ; 6d,R= Ph) were prepared starting from Ru 3 (CO) 12 (4)b yasingle step conversion with the respective phosphine 5 and benzoic acid (2a)a nalogouslyt oaprocedure described by Bianchi [35] (Scheme 4).…”
Section: Scheme3mentioning
confidence: 99%
“…[4,16,26] Ther esulting enol ester D undergoesa ni ntramolecular transesterification to the alkenyl derivative E,which after keto-enol tautomerizationand protonation releases the b-oxo ester andr egenerates the catalytically active ruthenium species (Scheme 3). [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.…”
Section: Introductionmentioning
confidence: 99%
“…[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.…”
Ruthenium complexes with the formulae Ru(CO) 2 (PR 3 ) 2 (O 2 CPh) 2 [6a-h;R = n-Bu, p-MeO-C 6 H 4 , p-Me-C 6 H 4 ,P h, p-Cl-C 6 H 4 , m-Cl-C 6 H 4 , p-CF 3 -C 6 H 4 , m,m'-(CF 3 ) 2 C 6 H 3 ]w ere prepared by treatment of triruthenium dodecacarbonyl [Ru 3 (CO) 12 ]w ith the respective phosphine and benzoic acid or by the conversion of Ru(CO) 3 (PR 3 ) 2 (8e-h)w ith benzoic acid. During the preparation of 8,r uthenium hydride complexes of type Ru(CO)(PR 3 ) 3 (H) 2 (9g, h)c ould be isolated as side products. Them olecular structures of the newly synthesizedc omplexes in the solid state are discussed. Compounds 6a-h were found to be highly effective catalysts in the addition of carboxylic acids to propargylic alcohols to give valuable b-oxo esters.T he catalyst screening revealed ac onsiderably influence of the phosphine'se lectronicn ature on the resulting activities. Theb est performances were obtained with complexes 6g and 6h,f eaturing electron-withdrawing phosphine ligands.A dditionally,c atalyst 6g is very active in the conversion of sterically demanding substrates,l eading to ab road substrate scope.T he catalytic preparation of simple as wella sc hallenging substrates succeeds with catalyst 6g in yields that often exceed those of established literature systems.F urthermore,t he reactions can be carriedo ut with catalyst loadings down to 0.1 mol% andr eactiont emperatures down to 50 8 8C.
Highly enantioselective benzylic hydroxylations of benzene derivatives (1-4) containing reactive functional groups were achieved for the first time with Pseudomonas monteilii TA-5 as biocatalyst, giving the corresponding (R)-benzylic alcohols 5-8 in 93-99% ee as the only products. Preparative biotransformations were demonstrated by the biohydroxylation of 1 and 2 with resting cells of P. monteilii TA-5 to afford (R)-5 in 94% ee and 66% yield and (R)-6 in 94% ee and 56% yield, respectively. The highly enantioselective biohydroxylations represent a simple access to (R)-benzylic alcohols containing reactive functional groups that are useful pharmaceutical intermediates and versatile chiral building blocks.
Ah igh-yielding synthesis of a-acyloxyketones using aN -heterocyclic-carbene (NHC)-catalyzed, oxidative ring-opening of epoxides with aromatic aldehydes is described. This regioselective,o xidative process utilizes a Nbromosuccinimide( NBS)/DMSO combination as the oxidant system and Et 3 Na st he base under mild reaction conditions. Scheme1.NHC-catalyzed,o xidative ring-opening of epoxides with aromatic aldehydes.[a] R.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.