Reactions oft-BuOK and Dibenzyl, Benzyl Allyl, and Allyl β-Keto Sulfide Complexes of the Chiral Rhenium Lewis Acid [(η5-C5H5)Re(NO)(PPh3)]+: Highly Diastereoselective or Chemoselective [2,3]-Sigmatropic Rearrangements
19
Citation
25
Reference
10
Related Paper
Citation Trend
Abstract:
Reaction of the dibenzyl sulfide complex [(η5-C5H5)Re(NO)(PPh3)(S(CH2Ph)2)]+TfO- (4a+TfO-) and t-BuOK (THF, −80 °C) gives the thiolate (η5-C5H5)Re(NO)(PPh3)(SCH(o-C6H4CH3)Ph) (5a; 99%) as a 96:4 mixture of SR,RS/SS,RR Re:C diastereomers. This transformation involves initial deprotonation of a benzyl group to give an ylide, followed by [2,3]- and [1,3]-rearrangements. A crystal structure of (SR,RS)-5a establishes the configuration. Similar reactions of the benzyl allyl sulfide complexes [(η5-C5H5)Re(NO)(PPh3)(S(CH2CRCH2)CH2Ph)]+TfO- (R = H, CH3) give mainly the thiolates (SS,RR)-(η5-C5H5)Re(NO)(PPh3)(SCH(CH2CRCH2)Ph), derived from benzyl group deprotonation. Some thiolates derived from allyl group deprotonation also form. Similar reactions of the allyl β-keto sulfide complexes [(η5-C5R5)Re(NO)(PPh3)(S(CH2CR'CR''2)CH2COPh)]+X- (R/R'/R'' = H/H/H, H/H/CH3, H/CH3/H, CH3/H/H) give the thiolates (η5-C5R5)Re(NO)(PPh3)(SCH(CR''2CR'CH2)COPh), derived from CH2COPh group deprotonation, as >96:<4 to 68:32 diastereomer mixtures. Reactions of 4a+TfO- with MeLi give mainly the [1,2]-rearrangement product (η5-C5H5)Re(NO)(PPh3)(SCH(CH2Ph)Ph) ((35−70):(65−30) diastereomer mixtures), which has been independently synthesized. The thiolate ligands are easily converted to free methyl sulfides. Mechanisms of diastereoselection, and similar reactions of organic sulfonium salts, are discussed.Keywords:
Diastereomer
Ylide
Scrap
Cite
Citations (10)
The removal of 75% of the lipid from bacteriorhodopsin caused the following: (i) decreased efficiency and rate of deprotonation of the protonated Schiff base (as monitored by absorption of the M412 intermediate); (ii) increased efficiency of deprotonation of deionized samples; (iii) a decrease by 1 unit in the pH at which deprotonation ceases; (iv) increased intensity of Eu3+ emission in Eu3+-regenerated deionized delipidated samples; (v) increased exposure of the Eu3+ sites to water; and (vi) elimination of the dependence of the deprotonation efficiency on the metal cation concentration. These results are discussed in terms of changes in the protein conformation upon delipidation, which in turn control the deprotonation mechanism.
Halobacteriaceae
Cite
Citations (30)
Cite
Citations (31)
Attempts to prepare rhenium hexachloride by the method described by Colton (2) have been unsuccessful. The products of the reaction were always impure rhenium oxotetrachloride and rhenium pentachloride. A compound of rhenium(VI), ReOCl 4 OPCl 3 , is shown to have a structure analogous to that of rhenium(V) ions [ReOX 4 .L] − in which the ligands are in a pseudooctahedral arrangement with L trans to the oxo-group (3). Reactions of ReOCl 4 and ReOCl 4 -OPCl 3 with pyridine and 2,2′-dipyridyl are described, and a scheme is proposed for the reactions of the products. Two stable complexes of perrhenyl chloride with the above amines have been obtained.
Perrhenate
Cite
Citations (22)
This chapter contains sections titled: Re Facts about Rhenium Discovery Where Should Elements 43 and 75 Be Looked For? The River Rhein but not the Region Masurien A Worldwide Search for Rhenium High Concentrations of Rhenium are Unexpectedly Found at Home! Rhenium Sources in Modern Times Modern Techniques for Manufacturing Rhenium Uses of Rhenium The Biological Role of Rhenium
Cite
Citations (0)
Cite
Citations (43)
Distance dependence of appended Lewis acids in N2H4 binding and deprotonation was evaluated within a series of zinc complexes.
Coordination sphere
Cite
Citations (12)
Cite
Citations (10)
Cite
Citations (12)
We have designed and prepared a series of rhenium complexes with 4,4′-bipyridyl as an electron-accepting unit. Electrochemical studies revealed that oxidation and reduction of these complexes occurred on the rhenium center and the 4,4′-bipyridyl skeleton, respectively. The redox potentials of the rhenium complexes are controllable by tuning the substituents on the 4,4′-bipyridyl skeleton and the coordinating groups to the rhenium center. We have also examined the reactivity of the rhenium complexes in electrochemical and photochemical CO2 reduction.
Reactivity
Center (category theory)
Cite
Citations (12)