Ana Castano - Academia.edu (original) (raw)

Papers by Ana Castano

Research paper thumbnail of Nucleophile Addition an (π-Allyl)palladium-Komplexe: Steuerung des Angriffs am zentralen oder an den terminalen Kohlenstoffatomen durch Liganden

Angewandte Chemie, 1995

bei niedrigeren Temperaturen als die von n-Hexan liegt, sollte dieser erste Massenverlust durch e... more bei niedrigeren Temperaturen als die von n-Hexan liegt, sollte dieser erste Massenverlust durch entropische und nicht durch energetische Effekte bestimmt sein. Dies bedeutet, daB die tiefe Temperatur, bei der der erste Desorptionspeak erscheint, durch einen relativ hohen Entropiegewinn bei der Desorption im Vergleich zu anderen n-Alkanen hervorgerufen sein miiBte. Dieser relativ hohe Entropiegewinn bei der Desorption kann nur auf einen niedrigen Wert der Entropie der adsorbierten n-Hexan-und n-Heptan-Molekiile, hervorgerufen durch eine raumlich eingeschrankte Position bei hohen Beladungen, zuruckzufuhren sein.

Research paper thumbnail of Allylsilanes as Carbon Nucleophiles in Intramolecular Pd(II)-Catalyzed 1,4Addition to Conjugated Dienes

Journal of The American Chemical Society, 1995

Nucleophilic additions to unsaturated hydrocarbons coordinated to transition metals are important... more Nucleophilic additions to unsaturated hydrocarbons coordinated to transition metals are important organometallic processes in organic synthesis.' In this area, palladium(II) complexes have proven to be efficient due to their ability to coordinate olefins and dienes and induce nucleophilic A few years ago we discovered the Pd(I1)-catalyzed 1 ,Coxidation of conjugated dienes involving regio-and stereoselective addition of nucleophiles to the 1-and 4-positions of the 1,3-diene.3 An intramolecular version of this Pd(I1)-catalyzed 1 ,Coxidation was developed recently and successfully applied to the construction of stereodefined heterocyclic systems (eq l)? However, the reaction has so far been limited to heteroatom nucleophiles, and attempts to employ different types of stabilized carbon nucleophiles in the side chain have been unsu~cessful.~-~ In our search to extend the reaction in eq 1 to C-C bond formation, we considered allylsilanes as possible carbon nucleophiles. We thought that the diene, activated by Pd(II), could be electrophilic enough to react in a Sakurai-type reaction with an allylsilane.8-10 In this communication we report on a (1) (a) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. C-C Bond formation was recently achieved by insertion of the diene in an in situ generated vinylpalladium species: Backvall, J. E.; Nilsson, Y. I. M.; Andersson, P. G.; Gatti, P. G.; Wu, J. Tetrahedron Lett. 1994, 35, 57 13-57 16. (6) The use of C-nucleophiles in the Pd(II)-promoted nucleophilic admtions to olefins has only been described with stoichiometric amounts of palladium. For a recent review, see: Hegedus, L. S . In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: Oxford, U.K., (7) Silylenol ethers react with olefins in the presence of stoichiometric Pd(I1) in a rather general process: (a) Toyota, M.; Wada, T.; Nishikawa, Y . ; Yanai, K.; Fukumoto, K. Synlett 1994, 597-598. (b) Toyota, M.; Nishikawa, Y.; Motoki, K.; Yoshida, N.; Fukumoto, K.

Research paper thumbnail of Nucleophilic Attack on(π-Allyl)palladium Complexes: Direction of the Attack to the Central or Terminal Carbon Atom by Ligand Control

Angewandte Chemie-international Edition, 1995

... 33. 1238. Nucleophilic Attack on (n-Allyl)palladium Complexes: Direction of the Attack to the... more ... 33. 1238. Nucleophilic Attack on (n-Allyl)palladium Complexes: Direction of the Attack to the Central or Terminal Carbon Atom by Ligand Control"" Ana M. Castaiio, Attila Aranyos. Krilmrin J. Szabo, and Jan-E. Bickvall* ... E = CO,Et. [*I Prof. Dr. J:E. Bickvall. Dr. A. M Castario. ...

Research paper thumbnail of Central versus Terminal Attack in Nucleophilic Addition to (π-Allyl)palladium Complexes. Ligand Effects and Mechanism

Organometallics, 1997

... Attila Aranyos, Kálmán J. Szabó, Ana M. Castaño, and Jan-E Bäckvall*. Department of Organic C... more ... Attila Aranyos, Kálmán J. Szabó, Ana M. Castaño, and Jan-E Bäckvall*. Department of Organic Chemistry, University of Uppsala, Box 531, S-751 21 Uppsala, Sweden. Organometallics , 1997, 16 (5), pp 1058–1064. DOI: 10.1021 ...

Research paper thumbnail of Allylsilanes as Carbon Nucleophiles in the Palladium-Catalyzed 1,4Oxidation of Conjugated Dienes

Chemistry-a European Journal, 2006

Palladium-catalyzed oxidation of cyclic 1,3-dienes 3, 5, 9, 11, and 13, with an allylsilane group... more Palladium-catalyzed oxidation of cyclic 1,3-dienes 3, 5, 9, 11, and 13, with an allylsilane group in the side chain, led to an intramolecular 1,4-syn-addition to the conjugated diene through a carbocyclization. Acyclic trienesilanes 7 also underwent analogous 1,4-oxidations. The reaction was carried out in acetone-acetic acid (2:1) with a slight excess of LiCl. p-Benzoquinone was employed as the oxidant and Li2PdCl4 as the catalyst. The reaction proceeds through an intramolecular trans addition of the allylsilane to a (π-diene)palladium complex to produce a bicyclic (π-allyl)palladium intermediate. Subsequent trans attack by chloride at the π-allyl intermediate gives the product. The intermediate (π-allyl)palladium complex was isolated and fully characterized. It was unambiguously demonstrated that the allylsilane had attacked the coordinated double bond trans to palladium (trans-carbopalladation). The use of CuCl2 as the oxidant, instead of p-benzoquinone, gave a less stereoselective addition, but interestingly, with the opposite stereochemistry.

Research paper thumbnail of Nucleophile Addition an (π-Allyl)palladium-Komplexe: Steuerung des Angriffs am zentralen oder an den terminalen Kohlenstoffatomen durch Liganden

Angewandte Chemie, 1995

bei niedrigeren Temperaturen als die von n-Hexan liegt, sollte dieser erste Massenverlust durch e... more bei niedrigeren Temperaturen als die von n-Hexan liegt, sollte dieser erste Massenverlust durch entropische und nicht durch energetische Effekte bestimmt sein. Dies bedeutet, daB die tiefe Temperatur, bei der der erste Desorptionspeak erscheint, durch einen relativ hohen Entropiegewinn bei der Desorption im Vergleich zu anderen n-Alkanen hervorgerufen sein miiBte. Dieser relativ hohe Entropiegewinn bei der Desorption kann nur auf einen niedrigen Wert der Entropie der adsorbierten n-Hexan-und n-Heptan-Molekiile, hervorgerufen durch eine raumlich eingeschrankte Position bei hohen Beladungen, zuruckzufuhren sein.

Research paper thumbnail of Allylsilanes as Carbon Nucleophiles in Intramolecular Pd(II)-Catalyzed 1,4Addition to Conjugated Dienes

Journal of The American Chemical Society, 1995

Nucleophilic additions to unsaturated hydrocarbons coordinated to transition metals are important... more Nucleophilic additions to unsaturated hydrocarbons coordinated to transition metals are important organometallic processes in organic synthesis.' In this area, palladium(II) complexes have proven to be efficient due to their ability to coordinate olefins and dienes and induce nucleophilic A few years ago we discovered the Pd(I1)-catalyzed 1 ,Coxidation of conjugated dienes involving regio-and stereoselective addition of nucleophiles to the 1-and 4-positions of the 1,3-diene.3 An intramolecular version of this Pd(I1)-catalyzed 1 ,Coxidation was developed recently and successfully applied to the construction of stereodefined heterocyclic systems (eq l)? However, the reaction has so far been limited to heteroatom nucleophiles, and attempts to employ different types of stabilized carbon nucleophiles in the side chain have been unsu~cessful.~-~ In our search to extend the reaction in eq 1 to C-C bond formation, we considered allylsilanes as possible carbon nucleophiles. We thought that the diene, activated by Pd(II), could be electrophilic enough to react in a Sakurai-type reaction with an allylsilane.8-10 In this communication we report on a (1) (a) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. C-C Bond formation was recently achieved by insertion of the diene in an in situ generated vinylpalladium species: Backvall, J. E.; Nilsson, Y. I. M.; Andersson, P. G.; Gatti, P. G.; Wu, J. Tetrahedron Lett. 1994, 35, 57 13-57 16. (6) The use of C-nucleophiles in the Pd(II)-promoted nucleophilic admtions to olefins has only been described with stoichiometric amounts of palladium. For a recent review, see: Hegedus, L. S . In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: Oxford, U.K., (7) Silylenol ethers react with olefins in the presence of stoichiometric Pd(I1) in a rather general process: (a) Toyota, M.; Wada, T.; Nishikawa, Y . ; Yanai, K.; Fukumoto, K. Synlett 1994, 597-598. (b) Toyota, M.; Nishikawa, Y.; Motoki, K.; Yoshida, N.; Fukumoto, K.

Research paper thumbnail of Nucleophilic Attack on(π-Allyl)palladium Complexes: Direction of the Attack to the Central or Terminal Carbon Atom by Ligand Control

Angewandte Chemie-international Edition, 1995

... 33. 1238. Nucleophilic Attack on (n-Allyl)palladium Complexes: Direction of the Attack to the... more ... 33. 1238. Nucleophilic Attack on (n-Allyl)palladium Complexes: Direction of the Attack to the Central or Terminal Carbon Atom by Ligand Control"" Ana M. Castaiio, Attila Aranyos. Krilmrin J. Szabo, and Jan-E. Bickvall* ... E = CO,Et. [*I Prof. Dr. J:E. Bickvall. Dr. A. M Castario. ...

Research paper thumbnail of Central versus Terminal Attack in Nucleophilic Addition to (π-Allyl)palladium Complexes. Ligand Effects and Mechanism

Organometallics, 1997

... Attila Aranyos, Kálmán J. Szabó, Ana M. Castaño, and Jan-E Bäckvall*. Department of Organic C... more ... Attila Aranyos, Kálmán J. Szabó, Ana M. Castaño, and Jan-E Bäckvall*. Department of Organic Chemistry, University of Uppsala, Box 531, S-751 21 Uppsala, Sweden. Organometallics , 1997, 16 (5), pp 1058–1064. DOI: 10.1021 ...

Research paper thumbnail of Allylsilanes as Carbon Nucleophiles in the Palladium-Catalyzed 1,4Oxidation of Conjugated Dienes

Chemistry-a European Journal, 2006

Palladium-catalyzed oxidation of cyclic 1,3-dienes 3, 5, 9, 11, and 13, with an allylsilane group... more Palladium-catalyzed oxidation of cyclic 1,3-dienes 3, 5, 9, 11, and 13, with an allylsilane group in the side chain, led to an intramolecular 1,4-syn-addition to the conjugated diene through a carbocyclization. Acyclic trienesilanes 7 also underwent analogous 1,4-oxidations. The reaction was carried out in acetone-acetic acid (2:1) with a slight excess of LiCl. p-Benzoquinone was employed as the oxidant and Li2PdCl4 as the catalyst. The reaction proceeds through an intramolecular trans addition of the allylsilane to a (π-diene)palladium complex to produce a bicyclic (π-allyl)palladium intermediate. Subsequent trans attack by chloride at the π-allyl intermediate gives the product. The intermediate (π-allyl)palladium complex was isolated and fully characterized. It was unambiguously demonstrated that the allylsilane had attacked the coordinated double bond trans to palladium (trans-carbopalladation). The use of CuCl2 as the oxidant, instead of p-benzoquinone, gave a less stereoselective addition, but interestingly, with the opposite stereochemistry.