(2,9 : 6,12-η-2,3,5,6-Tetrakis(methylene)-bicyclo[2.2.2]octane)zirconocene, an Isolable...
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Schmidt, G. Grundler, Synrhesis (1981) 885; d) R. R. Schmidt, 1. Eur. Symp. Carbohydr. Glycoconjugates, Vienna 198 1, [3] Recently TMS-OTf has been suggested as a coupling reagent for the syn- thesis of B-D-glycosides: a) T. Ogawa, K. Beppu, S. Nakabayashi, Carbo- hydr. Res. 93 (1981) C6; b) see [6a] p. 195. [5] 3,4,6-tri-O-acetyl-2-azido-2-deoxy-D-galactose was prepared by azidoni- tration of the corresponding galactal after R. U. Lemieux, R. M. Ratcliffe, Can. J. Chem. 57 (1979)1244). [6] a) H. Paulsen, Angew. Chem. 94 (1982)184; Angew. Chem. Int. Ed. Engl. 21 (1982) 155: b) H. Paulsen, A. Bunsch, Carbohydr. Res. 100 (1982) 143. (2,9 : 6,12-q-2,3,5,6-Tetrakis(methylene)- bicyclol2.2.2loctane)zirconocene, an Isolable Bis(olefin)zirconium(Ir) Compound** By Gerhard Erker*, Klaus Engel, and Pierre Vogel The equilibration between bis(o1efin)transition-metal complexes and metallacyclopentanes is of great impor- tance for the development of metal-catalyzed processes for the conversion of olefin substrates[Ib1. Due to their rapid rearrangement to the more favorable metallacycles, bis(olefin) complexes of group IV transition metals, in contrast to those of other transition metals, have not been observed so far[31. By using the olefinic ligand 2,3,5,6-tetra- kis(methylene)bicyclo[2.2.2]octane 6[7aI, we have now been able to prepare, to our knowledge the first, bis(o1efin)zir- conocene complex isolable at room temperature. Bis(q5-cyclopentadienyl)zirconium(~~), generated in situ from diphenylzirconocene by photochemically induced re- ductive elimination of biphenylI5I, reacts with 6 by coordi- nation of the 1,Cdiene unit to give the title compound 7. 7, which is only moderately soluble in the aromatic sol- vents used, is very sensitive to air and moisture; like ha- loalkanes, oxygen also liberates the ligand 6. Thermolysis of 7 (benzene, 60 "C, tl,z= 5 min) leads to formation of its isomer 8, in which one of the two conjugated diene-units of 6 is bound to the zirconocene group. The bis(o1efin)zir- conocene complex 7 can be quantitatively recovered upon irradiation (HPK 125, Pyrex filter) of 8 in benzene solu- tion at room temperature. Tables 1 and 2 (selection). 1H-['3C-]NMR data of the zirconocene complexes 7 and 8 [a]. 7 8 4.46, 4.39 br. s (< I) [96.2 t (157)l I17.8 t (152)l =CHI (free) =CHI (compl.) 2.30,-0.02 d (3.6) 2.51,0.14 d (11.0 CP 5.07, 4.68 [104.0, 104.5] 5.50, 5.30 [104.0, 106.01 5.13, 4.60 br. s (< 1) [I03 t (I58)l [45.4 dd (130; 145)j [a] C6D6, 6 rel. TMS, 2JHH ['JcH] in Hz [*I Priv.-Doz. Dr. G. Erker, K. Engel Abteilung fur Chemie der Ruhr-Universitat Postfach 102148,D-4630 Bochum 1 (Germany) Prof. Dr. P. Vogel lnstitut fur Organische Chemie der Universitat Rue de la Barre 2, CH-1005 Lausanne (Switzerland) schung des Landes Nordrhein-Westfalen. [**I This work was supported by the Minister fur Wissenschaft und For- According to the NMR spectra (Tables 1 and 2) 7 is characterized by a markedly much more pronounced n- complex character than 8. The similarity of the spectra of 7 and those of the previously known mononuclear (s-trans- q4-diene)zirconocene complexes[61 is remarkable. From the finding that 7 can be readily and reversibly converted into a (q4-diene)metal complex 8 of "normal" structure and stability it appears promising that the observation of other bis(o1efin) complexes of early transition metals equilibrat- ing with the isomeric metallacyclopentanes might also be possible. Received: May 21, 1982 [Z 51 IE] revised: July 16, 1982 German version: ,4ngew. Chem. 94 (1982)791 The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982. 1746-1756 [I] b) A. Stockis, R. Hoffmann, 1. Am. Chem. SOC. 102 (1980) 2952. [3] J. X. McDermott, M. E. Wilson, G. M. Whitesides, J. Am. Chem. SOC. 98 (1976) 6529; D. R. McAlister, D. K. Erwin, J. E. Bercaw, ibid. 100 (1978) 5966. [5] G. Erker, J. Organomet. Chem. 134 (1977)189. [6] G. Erker, J. Wicher, K. Engel, F. Rosenfeldt, W. Dietrich, C. Kriiger, J. 171 a) A. Chollet, M. Wismer, P. Vogel, Tetrahedron Lett. 1976. 4271. Am. Chem. SOC. 102 (1980) 6344. Indirect Electrochemical Regeneration of NADH by a Bipyridinerhodium(1) Complex as Electron-Transfer Agent** By Rainer Wienkamp and Eberhard Steckhan* Because of its significance in enzyme-catalyzed syn- theses, there is considerable interest in straightforward and effective methods for the regeneration of NADH from NADO. We report here preliminary results on the indirect electrochemical regeneration of NADH from NAD@. The direct electrochemical reduction of NADe at - 1.1 V us. SCE leads essentially to inactive dimers and even at - 1.8 V, active NADH is only formed in 50% yield"]. We have now succeeded in reducing NAD@to NADH using the electrochemically generated two-electron transfer agent [Rh(bpy),]@, which is generated cathodically from [Rh(bpy)3]30151. In this way an enzyme is not required for the transfer of two electrons"' to the coenzyme. The regen- erated NADH is oxidized by cyclohexanone under cataly- sis of horse liver alcohol-dehydrogenase (HLAD) [eq. We performed the reactions in 40-60 mL tris-HC1 buf- fer (pH 9) in divided cells using a graphite cathode, plat- inum anode, and a glass frit as diaphram at - 850 to -950 mV us. Ag/AgCl in discontinuous or continuous working mode [eq. (b)] (Table 1). In experiment 3, 1.5 x mmol of NAD dimer could be determined[lhlcorresponding to 0.9% of NAD@per cy- cle. At lower working potentials dimerization can be dim- inished. Using the discontinuous working mode NADH can be separated chromatographically and determined from its absorbance["'. The small number of regenerative cycles does not arise from the instability of the electron transfer agent or from that of the coenzyme or enzyme; it results solely from pas- @)I. [*] Prof. Dr. E. Steckhan, R. Wienkamp Institut fur Organische Chemie der Universitat Gerhard-Domagk-Strasse I, D-5300 Bonn 1 (Germany) [**I Indirect Electrochemical Processes, Part 13. This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen 1ndustrie.-Part 12: S. Dapperheld, E. Steckhan, Angew. Chem. 94 (1982)785: Angew. Chem. In(. Ed. Engl. 21 (1982)1730: Angew. Chem. Suppl. 1982, 780 782 0 Verlag Chemie GmbH. 6940 Weinheim, 1982 0570-0833/82/1010-0782 $02.50/0 Angew. Chem. Int. Ed. Engl. 21 (1982) No. I0
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Transcript of (2,9 : 6,12-η-2,3,5,6-Tetrakis(methylene)-bicyclo[2.2.2]octane)zirconocene, an Isolable...
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Schmidt, G. Grundler, Synrhesis (1981) 885; d) R. R. Schmidt, 1. Eur. Symp. Carbohydr. Glycoconjugates, Vienna 198 1,
[3] Recently TMS-OTf has been suggested as a coupling reagent for the syn- thesis of B-D-glycosides: a) T. Ogawa, K. Beppu, S. Nakabayashi, Carbo- hydr. Res. 93 (1981) C6; b) see [6a] p. 195.
[5] 3,4,6-tri-O-acetyl-2-azido-2-deoxy-D-galactose was prepared by azidoni- tration of the corresponding galactal after R. U. Lemieux, R. M. Ratcliffe, Can. J. Chem. 57 (1979) 1244).
[6] a) H. Paulsen, Angew. Chem. 94 (1982) 184; Angew. Chem. Int. Ed. Engl. 21 (1982) 155: b) H. Paulsen, A. Bunsch, Carbohydr. Res. 100 (1982) 143.
(2,9 : 6,12-q-2,3,5,6-Tetrakis(methylene)- bicyclol2.2.2loctane)zirconocene, an Isolable Bis(olefin)zirconium(Ir) Compound** By Gerhard Erker*, Klaus Engel, and Pierre Vogel
The equilibration between bis(o1efin)transition-metal complexes and metallacyclopentanes is of great impor- tance for the development of metal-catalyzed processes for the conversion of olefin substrates[Ib1. Due to their rapid rearrangement to the more favorable metallacycles, bis(olefin) complexes of group IV transition metals, in contrast to those of other transition metals, have not been observed so far[31. By using the olefinic ligand 2,3,5,6-tetra- kis(methylene)bicyclo[2.2.2]octane 6[7aI, we have now been able to prepare, to our knowledge the first, bis(o1efin)zir- conocene complex isolable a t room temperature. Bis(q5-cyclopentadienyl)zirconium(~~), generated in situ
from diphenylzirconocene by photochemically induced re- ductive elimination of biphenylI5I, reacts with 6 by coordi- nation of the 1,Cdiene unit to give the title compound 7 . 7, which is only moderately soluble in the aromatic sol-
vents used, is very sensitive to air and moisture; like ha- loalkanes, oxygen also liberates the ligand 6. Thermolysis of 7 (benzene, 60 "C, tl,z= 5 min) leads to formation of its isomer 8, in which one of the two conjugated diene-units of 6 is bound to the zirconocene group. The bis(o1efin)zir- conocene complex 7 can be quantitatively recovered upon irradiation (HPK 125, Pyrex filter) of 8 in benzene solu- tion at room temperature.
Tables 1 and 2 (selection). 1H-['3C-]NMR data of the zirconocene complexes 7 and 8 [a].
7 8
4.46, 4.39 br. s (< I ) [96.2 t (157)l
I17.8 t (152)l
=CHI (free)
=CHI (compl.) 2.30, -0.02 d (3.6) 2.51, 0.14 d (11.0
CP 5.07, 4.68 [104.0, 104.5] 5.50, 5.30 [104.0, 106.01
5.13, 4.60 br. s (< 1) [I03 t (I58)l
[45.4 dd (130; 145)j
[a] C6D6, 6 rel. TMS, 2JHH ['JcH] in Hz
[*I Priv.-Doz. Dr. G. Erker, K. Engel Abteilung fur Chemie der Ruhr-Universitat Postfach 1021 48, D-4630 Bochum 1 (Germany) Prof. Dr. P. Vogel lnstitut fur Organische Chemie der Universitat Rue de la Barre 2, CH-1005 Lausanne (Switzerland)
schung des Landes Nordrhein-Westfalen. [**I This work was supported by the Minister fur Wissenschaft und For-
According to the NMR spectra (Tables 1 and 2) 7 is characterized by a markedly much more pronounced n- complex character than 8. The similarity of the spectra of 7 and those of the previously known mononuclear (s-trans- q4-diene)zirconocene complexes[61 is remarkable. From the finding that 7 can be readily and reversibly converted into a (q4-diene)metal complex 8 of "normal" structure and stability it appears promising that the observation of other bis(o1efin) complexes of early transition metals equilibrat- ing with the isomeric metallacyclopentanes might also be possible.
Received: May 21, 1982 [Z 51 IE] revised: July 16, 1982
German version: ,4ngew. Chem. 94 (1982) 791 The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982. 1746-1756
[I] b) A. Stockis, R. Hoffmann, 1. Am. Chem. SOC. 102 (1980) 2952. [3] J. X. McDermott, M. E. Wilson, G. M. Whitesides, J. Am. Chem. SOC. 98
(1976) 6529; D. R. McAlister, D. K. Erwin, J. E. Bercaw, ibid. 100 (1978) 5966.
[5] G. Erker, J. Organomet. Chem. 134 (1977) 189. [6] G. Erker, J. Wicher, K. Engel, F. Rosenfeldt, W. Dietrich, C. Kriiger, J.
171 a) A. Chollet, M. Wismer, P. Vogel, Tetrahedron Lett. 1976. 4271. Am. Chem. SOC. 102 (1980) 6344.
Indirect Electrochemical Regeneration of NADH by a Bipyridinerhodium(1) Complex as Electron-Transfer Agent** By Rainer Wienkamp and Eberhard Steckhan*
Because of its significance in enzyme-catalyzed syn- theses, there is considerable interest in straightforward and effective methods for the regeneration of NADH from NADO. We report here preliminary results on the indirect electrochemical regeneration of NADH from NAD@.
The direct electrochemical reduction of NADe at - 1 . 1 V us. SCE leads essentially to inactive dimers and even at - 1.8 V, active NADH is only formed in 50% yield"].
We have now succeeded in reducing NAD@ to NADH using the electrochemically generated two-electron transfer agent [Rh(bpy),]@, which is generated cathodically from [Rh(bpy)3]30151. In this way an enzyme is not required for the transfer of two electrons"' to the coenzyme. The regen- erated NADH is oxidized by cyclohexanone under cataly- sis of horse liver alcohol-dehydrogenase (HLAD) [eq.
We performed the reactions in 40-60 mL tris-HC1 buf- fer (pH 9) in divided cells using a graphite cathode, plat- inum anode, and a glass frit as diaphram at - 850 to -950 mV us. Ag/AgCl in discontinuous or continuous working mode [eq. (b)] (Table 1).
In experiment 3, 1.5 x mmol of NAD dimer could be determined[lhl corresponding to 0.9% of NAD@ per cy- cle. At lower working potentials dimerization can be dim- inished. Using the discontinuous working mode NADH can be separated chromatographically and determined from its absorbance["'.
The small number of regenerative cycles does not arise from the instability of the electron transfer agent or from that of the coenzyme or enzyme; it results solely from pas-
@)I.
[*] Prof. Dr. E. Steckhan, R. Wienkamp Institut fur Organische Chemie der Universitat Gerhard-Domagk-Strasse I , D-5300 Bonn 1 (Germany)
[**I Indirect Electrochemical Processes, Part 13. This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen 1ndustrie.-Part 12: S. Dapperheld, E. Steckhan, Angew. Chem. 94 (1982) 785: Angew. Chem. I n ( . Ed. Engl. 21 (1982) 1730: Angew. Chem. Suppl. 1982, 780
782 0 Verlag Chemie GmbH. 6940 Weinheim, 1982 0570-0833/82/1010-0782 $02.50/0 Angew. Chem. Int. Ed. Engl. 21 (1982) No. I0
![INDEX [] · S1 Supporting information for Zirconium–MOF catalysed selective synthesis of α- hydroxyamide via transfer hydrogenation of α-ketoamide Ashish A. Mishra† and Bhalchandra](https://static.fdocument.org/doc/165x107/602b5ab73fe4e62cda6bca69/index-s1-supporting-information-for-zirconiumamof-catalysed-selective-synthesis.jpg)
